Form 424B3

PIMCO Flexible Municipal Income Fund

Prospectus

April 30, 2021 (as supplemented May 14, 2021)

PIMCO Flexible Municipal Income Fund

	Common Shares
	Institutional Class	Class A-1	Class A-2*	Class A-3**
PIMCO Flexible Municipal Income Fund	PMFLX	PMAAX	PMALX	PMFAX

Class A-2 was formerly called Class A-1.

Class A-3 was formerly called Class A-2.

Neither the U.S. Securities and Exchange Commission nor the U.S. Commodity Futures Trading Commission has approved or disapproved of these securities or determined that this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

As permitted by regulations adopted by the Securities and Exchange Commission, paper copies of the Fund’s annual and semi-annual shareholder reports will no longer be sent by mail, unless you specifically request paper copies of the reports from the Fund or from your financial intermediary, such as a broker-dealer or bank. Instead, the reports will be made available on the Fund’s website, pimco.com/literature, and you will be notified by mail each time a report is posted and provided with a website link to access the report.

If you already elected to receive shareholder reports electronically, you will not be affected by this change and you need not take any action. You may elect to receive shareholder reports and other communications from the Fund electronically by visiting pimco.com/edelivery or by contacting your financial intermediary, such as a broker-dealer or bank.

You may elect to receive all future reports in paper free of charge. If you own these shares through a financial intermediary, such as a broker-dealer or bank, you may contact your financial intermediary to request that you continue to receive paper copies of your shareholder reports. If you invest directly with the Fund, you can inform the Fund that you wish to continue receiving paper copies of your shareholder reports by calling 844.312.2113. Your election to receive reports in paper will apply to all funds held with the fund complex if you invest directly with the Fund or to all funds held in your account if you invest through a financial intermediary, such as a broker-dealer or bank.

The Fund. PIMCO Flexible Municipal Income Fund (the “Fund”) is a non-diversified, closed-end management investment company that continuously offers its shares of beneficial interest, par value of $0.00001 per share (the “Common Shares”) and is operated as an “interval fund.” The Fund currently has four separate classes of Common Shares: Institutional Class, Class A-1, Class A-2 and Class A-3.

Investment Objectives. The Fund seeks to provide high current income exempt from federal income tax. Capital appreciation is a secondary objective.

Investment Strategy. The Fund attempts to achieve these objectives by investing, under normal circumstances, at least 80% of its net assets (plus any borrowings for investment purposes) in a portfolio of municipal bonds and other municipal securities, the interest from which, in the opinion of bond counsel for the issuer at the time of issuance (or on the basis of other authority believed by PIMCO to be reliable), is exempt from federal income tax (i.e., excluded from gross income for federal income tax purposes but not necessarily exempt from the federal alternative minimum tax or from the income taxes of any state or local government) as described under “Portfolio Contents” below. To a lesser extent, the Fund also expects to invest in a full range of preferred securities with an emphasis on preferred securities that, at the time of issuance, are eligible to pay dividends that qualify for certain favorable federal income tax treatment.

The Fund does not target a specific duration or maturity for the municipal bonds and other securities in which it invests, and the Fund’s average portfolio duration, as calculated by PIMCO, may vary significantly depending on market conditions and other factors. There is no limit on the maturity or duration of any individual security in which the Fund may invest.

Portfolio Contents. The Fund will invest, under normal circumstances, at least 80% of its net assets (plus any borrowings for investment purposes) in a portfolio of municipal bonds and other municipal securities, the interest from which, in the opinion of bond counsel for the issuer at the time of issuance (or on the basis of other authority believed by PIMCO to be reliable), is exempt from federal income tax (i.e., excluded from gross income for federal income tax purposes but not necessarily exempt from the federal alternative minimum tax or from the income taxes of any state or local government). The Fund’s 80% policy is a fundamental policy, which may not be changed without the approval of the holders of a majority of the Fund’s outstanding Common Shares and Preferred Shares (as defined below) voting together as a single class, and of the holders of a majority of the outstanding Preferred Shares voting as a separate class.

The Fund may invest without limit in municipal bonds and other securities that are rated below investment grade (or unrated but determined by PIMCO to be of comparable quality). Bonds of below investment grade quality are regarded as having predominantly speculative characteristics with respect to capacity to pay interest and repay principal and are commonly referred to as “junk bonds.” The Fund may also invest without limit in investment grade securities. The Fund may invest more than 25% of its total assets in bonds of issuers in California and New York.

The Fund may invest the balance of its assets (i.e., not towards its 80% policy noted above) in securities and assets that produce taxable income. Such assets are normally expected to include preferred securities, with an emphasis on preferred securities that, at the time of issuance, are eligible to pay dividends that qualify for certain favorable federal income tax treatment, such as dividends that are treated as qualified dividend income and eligible for the dividends received deduction (in each instance, provided certain requirements and holding periods are satisfied).

It is possible that the Fund could own no preferred securities at any given time, including, for example, if municipal securities are expected to produce a higher yield than preferred securities on an after-tax basis.

Subject to the Fund’s investment policies described above, the Fund may invest in other securities, including commercial paper, securities eligible for resale under Rule 144A of the Securities Act of 1933, as amended (the “1933 Act”), and other privately placed securities, and other debt securities subject to federal income tax, including privately negotiated debt obligations with respect to which the principal and/or interest is determined by reference to the performance of a benchmark asset, market or interest rate (an “embedded index”), such as specific securities, an index of securities or specified interest rates, or the differential performance of two assets or markets, such as indexes reflecting bonds. The rate of interest on an income-producing security may be fixed, floating or variable. The Fund may also engage in credit spread trades. A credit spread trade is an investment position relating to a difference in the prices or interest rates of two bonds or other securities, in which the value of the investment position is determined by changes in the difference between the prices or interest rates, as the case may be, of the respective securities. The Fund may purchase and sell securities on a when-issued, delayed delivery or forward commitment basis and may engage in short sales. The Fund may invest in trust certificates issued in tender option bond programs. In these programs, a trust typically issues two classes of certificates and uses the proceeds to purchase municipal securities having relatively long maturities and bearing interest at a fixed interest rate substantially higher than prevailing short-term tax-exempt rates. The Fund may also invest up to 5% of its total assets in securities of other investment companies, including closed-end funds, exchange-traded funds and other open-end funds, that invest primarily in municipal bonds and other municipal securities of the types in which the Fund may invest directly.

The Fund may, but is not required to, invest in derivative instruments, such as options, futures or forward contracts or swap agreements. For purposes of the Fund’s 80% policy, the Fund values its derivative instruments based on their market value. The Fund may, without limitation, seek to obtain market exposure to the securities in which it primarily invests by entering into a series of purchase and sale contracts or by using other investment techniques (such as buy backs or dollar rolls).

To the extent consistent with the applicable liquidity requirements for interval funds under Rule 23c-3 of the Investment Company Act of 1940, as amended, the Fund may invest without limit in illiquid investments.

Interval Fund/Repurchase Offers. The Fund is an “interval fund,” a type of fund which, in order to provide liquidity to shareholders, has adopted a fundamental investment policy to make quarterly offers to repurchase between 5% and 25% of its outstanding Common Shares at net asset value. Subject to applicable law and approval of the Fund’s Board of Trustees, for each quarterly repurchase offer, the Fund currently expects to offer to repurchase 10% of the Fund’s outstanding Common Shares at net asset value.

Leverage. The Fund currently utilizes leverage through its outstanding Variable Rate MuniFund Term Preferred Shares (“VMTP Shares”) and Remarketable Variable Rate MuniFund Term Preferred Shares (“RVMTP Shares” and, together with VMTP Shares and any other preferred shares the Fund may have outstanding, “Preferred Shares”) and the use of tender option bonds. The Fund may also choose to add leverage through the issuance of additional Preferred Shares or the use of reverse repurchase agreements, credit default swaps, dollar rolls or borrowings, such as through bank loans or commercial paper and/or other credit facilities. The Fund may issue additional Preferred Shares without the approval of holders of Common Shares (“Common Shareholders”). If the Fund issues additional Preferred Shares in the future, all costs and expenses relating to the issuance and ongoing maintenance of the Preferred Shares will be borne by the Common Shareholders, and these costs and expenses may be significant. The Fund may also enter into transactions other than those noted above that may give rise to a form of leverage including, among others, futures and forward contracts (including foreign currency exchange contracts), total return swaps and other derivative transactions, loans of portfolio securities, short sales and when-issued, delayed delivery and forward commitment transactions. The Fund utilizes leverage, including, without limitation, tender option bonds, opportunistically and may choose to increase or decrease, or eliminate entirely, its use of leverage over time and from time to time based on PIMCO’s assessment of the yield curve environment, interest rate trends, market conditions and other factors. The Fund may also determine to increase its leverage through the issuance of additional Preferred Shares, or decrease the leverage it currently maintains through its outstanding Preferred Shares through Preferred Share redemptions or tender offers and may or may not determine to replace such leverage through other sources. By using leverage, the Fund seeks to obtain a higher return for holders of Common Shares than if the Fund did not use leverage. Leveraging is a speculative technique and there are special risks and costs involved. There can be no assurance that a leveraging strategy will be used or that it will be successful during any period in which it is employed.

Investment Manager. The Fund’s investment manager is Pacific Investment Management Company LLC (“PIMCO” or the “Investment Manager”). As of December 31, 2020, PIMCO had approximately $2.21 trillion in assets under management.

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The Fund’s Common Shares are not listed for trading on any national securities exchange. The Fund’s Common Shares have no trading market and no market is expected to develop.

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An investment in the Fund is not suitable for investors who need certainty about their ability to access all of the money they invest in the short term.

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Even though the Fund will make periodic repurchase offers for its outstanding Common Shares, subject to the limitations described herein, investors should consider Common Shares of the Fund to be an illiquid investment.

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There is no guarantee that you will be able to sell your Common Shares at any given time or in the quantity that you desire.

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There is no assurance that the Fund will be able to make any distributions or maintain a certain level of distributions to Common Shareholders.

Institutional Class, Class A-1, Class A-2 and Class A-3 Common Shares each represent an investment in the same portfolio of investments, but each class has its own expense structure and arrangements for shareholder services or distribution, which allows you to choose the class that best fits your situation and eligibility requirements. Class A-1, Class A-2 and Class A-3 Common Shares are primarily offered and sold to retail investors by certain broker-dealers which are members of the Financial Industry Regulatory Authority (“FINRA”) and which have agreements with the Distributor to sell Class A-1, Class A-2 and/or Class A-3 Common Shares, but may be made available through other financial firms, including banks and trust companies and to specified benefit plans. Only certain investors are eligible to purchase Institutional Class Common Shares. See “Plan of Distribution – Share Classes.”

Institutional Class

The minimum initial investment for Institutional Class Common Shares is $1 million per account, except that the minimum investment may be modified for certain financial firms that submit orders on behalf of their customers, the Trustees and certain employees and their extended family members of PIMCO and its affiliates. There is no minimum subsequent investment amount. See “Plan of Distribution – Share Classes.”

Class A-1, Class A-2 and Class A-3

The minimum initial investment for Class A-1, Class A-2 and Class A-3 Common Shares is $2,500 per account, except that the minimum investment may be modified for certain financial firms that submit orders on behalf of their customers, the Trustees and certain employees and their extended family members of PIMCO and its affiliates. The minimum subsequent investment amount for Class A-1, Class A-2 and Class A-3 Common Shares is $50. See “Plan of Distribution - Purchasing Shares.”

Investors should carefully consider the Fund’s risks and investment objectives, as an investment in the Fund may not be appropriate for all investors and is not designed to be a complete investment program.

Before buying any of the Fund’s Common Shares, you should read the discussion of the principal risks of investing in the Fund in “Principal Risks of the Fund” beginning on page 35 of this prospectus. No assurance can be given that the Fund’s investment objectives will be achieved, and you could lose all of your investment in the Fund.

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The Fund’s Common Shares do not represent a deposit or obligation of, and are not guaranteed or endorsed by, any bank or other insured depository institution, and are not federally insured by the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other government agency.

Please read this prospectus carefully before deciding whether to invest and retain it for future reference. It sets forth concisely the information about the Fund that a prospective investor ought to know before investing in the Fund. The Fund has filed with the Securities and Exchange Commission (“SEC”) a Statement of Additional Information dated April 30, 2021, as supplemented from time to time, containing additional information about the Fund (the “Statement of Additional Information”). The Statement of Additional Information is incorporated by reference into this prospectus, which means it is part of this prospectus for legal purposes. The Fund also produces both annual and semi-annual reports that will contain important information about the Fund. Copies of the Statement of Additional Information and the Fund’s annual and semi-annual reports, when available, may be obtained upon request, without charge, by calling 844.312.2113 or by writing to the Fund at Regulatory Document Request, 650 Newport Center Drive, Newport Beach, California 92660. You may also call this toll-free telephone number to request other information about the Fund or to make shareholder inquiries. The Statement of Additional Information and the most recent annual and semi-annual reports are available free of charge on the Fund’s website at www.pimco.com. Information on, or accessible through, the Fund’s website is not a part of, and is not incorporated into, this prospectus. You may also access reports and other information about the Fund on the EDGAR Database on the SEC’s Internet site at www.sec.gov. You may get copies of this information, with payment of a duplication fee, by electronic request at the following E-mail address: publicinfo@sec.gov.

You should rely only on the information contained or incorporated by reference in this prospectus. The Fund has not authorized anyone to provide you with inconsistent information. If anyone provides you with inconsistent information, you should not assume that the Fund has authorized or verified it. The Fund is not making an offer of these securities in any state where the offer is not permitted. You should not assume that the information contained in this prospectus is accurate as of any date other than the date on the front of this prospectus. The Fund’s business, financial condition, results of operations and prospects may have changed since that date.

PIMCO Flexible Municipal Income Fund

Prospectus Summary

This is only a summary. This summary may not contain all of the information that you should consider before investing in Common Shares of the Fund. You should review the more detailed information contained in this prospectus and in the Statement of Additional Information. In particular, you should carefully read the risks of investing in the Fund’s Common Shares, as discussed under “Principal Risks of the Fund.”

The Fund

PIMCO Flexible Municipal Income Fund (the “Fund”) is a non-diversified, closed-end management investment company that continuously offers its shares of beneficial interest, par value of $0.00001 per share (the “Common Shares”). The Fund commenced operations on March 15, 2019. The Fund is operated as an “interval fund” (as defined below). The Fund currently has four separate classes of Common Shares: Institutional Class, Class A-1, Class A-2 and Class A-3.

Continuous Offering

The Fund continuously offers its Common Shares through PIMCO Investments LLC (the “Distributor”), as principal underwriter, on a best efforts basis. Institutional Class, Class A-1 and Class A-3 Common Shares are sold at their offering price, which is net asset value per share. While neither the Fund nor the Distributor impose an initial sales charge on Institutional Class, Class A-1 or Class A-3 Common Shares, if you buy Institutional Class, Class A-1 or Class A-3 Common Shares through certain financial firms, they may directly charge you transaction or other fees in such amount as they may determine. Please consult your financial firm for additional information.

Unless you are eligible for a waiver, Class A-2 Common Shares will be sold at a public offering price equal to their net asset value plus an initial sales charge. The initial sales charge varies depending upon the size of your purchase. The minimum initial investment amount for Institutional Class Common Shares is $1 million per account. The minimum initial investment amount for Class A-1, Class A-2 and Class A-3 Common Shares is $2,500 per account. These investment minimums may be modified for certain financial firms that submit orders on behalf of their customers, the Trustees and certain employees and their extended family members of PIMCO and its affiliates. The minimum subsequent investment amount for Class A-1, Class A-2 and Class A-3 Common Shares is $50. Proceeds from the offering will be held by the Fund’s custodian.

For additional information regarding each share class please see “Plan of Distribution – Share Classes” in this prospectus. The Fund reserves the right to reject a purchase order for any reason. Shareholders will not have the right to redeem their Common Shares. However, as described below, in order to provide some liquidity to shareholders, the Fund will conduct periodic repurchase offers for a portion of its outstanding Common Shares.

Periodic Repurchase Offers

The Fund is an “interval fund,” a type of fund which, in order to provide liquidity to shareholders, has adopted a fundamental investment policy to make quarterly offers to repurchase between 5% and 25% of its outstanding Common Shares at NAV. Subject to applicable law and approval of the Fund’s Board of Trustees (the “Board” or “Board of Trustees”), for each quarterly repurchase offer, the Fund currently expects to offer to repurchase 10% of the Fund’s outstanding Common Shares at NAV. Written notification of each quarterly repurchase offer (the “Repurchase Offer Notice”) will be sent to shareholders at least 21 calendar days before the repurchase request deadline (i.e., the date by which shareholders can tender their Common Shares in response to a repurchase offer) (the “Repurchase Request Deadline”). Subject to Board approval, Repurchase Request Deadlines are expected to occur each February, May, August and November, and Repurchase Offer Notices are expected to be sent each January, April, July and October preceding each such Repurchase Request Deadline. The Fund’s Common Shares are not listed on any securities exchange, and the Fund does not anticipate that a secondary market will develop for its Common Shares. Accordingly, you may not be able to sell Common Shares when and/or in the amount that you desire. Investors should consider Common Shares of the Fund to be an illiquid investment. Thus, the Common Shares are appropriate only as a long-term investment. In addition, the Fund’s repurchase offers may subject the Fund and shareholders to special risks. See “Principal Risks of the Fund — Repurchase Offers Risk.”

Investment Objectives and Strategies

Investment Objectives

The Fund seeks to provide high current income exempt from federal income tax. Capital appreciation is a secondary objective. The Fund attempts to achieve these objectives by investing, under normal circumstances, at least 80% of its net assets (plus any borrowings for investment purposes) in a portfolio of municipal bonds and other municipal securities, the interest from which, in the opinion of bond counsel for the issuer at the time of issuance (or on the basis of other authority believed by PIMCO to be reliable), is exempt from federal income tax (i.e., excluded from gross income for federal income tax purposes but not necessarily exempt from the federal alternative minimum tax or from the income taxes of any state or local government) as described under “Portfolio Contents” below. In pursuing its investment objectives, the Fund may invest without limit in investment grade securities and may invest without limit in below investment grade securities.

Portfolio Management Strategies

Flexible allocation strategy. The Fund seeks to achieve its investment objectives by utilizing a flexible, multi-sector tax-efficient approach to investing, under normal circumstances, primarily in municipal bonds and other municipal securities that carry interest payments that are exempt from federal income tax. The principal issuers

1 PIMCO Flexible Municipal Income Fund | Prospectus

Prospectus

of these securities are state and local governments and their agencies located in any of the fifty states, as well as in Puerto Rico and other U.S. territories and possessions. To a lesser extent, the Fund also expects to invest in a full range of preferred securities with an emphasis on preferred securities that, at the time of issuance, are eligible to pay dividends that qualify for certain favorable federal income tax treatment. With PIMCO’s macroeconomic analysis as the basis for top-down investment decisions, the Fund seeks to offer investors an actively-managed municipal bond portfolio that aims to capitalize on what PIMCO believes are attractive opportunities across states and sectors within the U.S. municipal market.

Investment selection strategies. In selecting securities for the Fund, PIMCO develops an outlook for interest rates and the economy, analyzes credit and call risks, and uses other security selection techniques. The proportion of the Fund’s assets committed to investment in securities with particular characteristics (such as quality, sector, interest rate or maturity) varies based on PIMCO’s outlook for the U.S. economy. PIMCO attempts to preserve and enhance the value of the Fund’s holdings relative to the municipal bond market, generally, using proprietary analytical models that test and evaluate the sensitivity of those holdings to changes in interest rates and yield relationships. There is no guarantee that PIMCO’s investment selection techniques will produce the desired results.

Credit quality. The Fund may invest without limit in municipal bonds and other securities of any credit quality, including without limitation, in securities that are, at the time of purchase, rated below investment grade (below Baa3 by Moody’s Investors Service, Inc. (“Moody’s”) or below BBB- by either S&P Global Ratings (“S&P”) or Fitch, Inc. (“Fitch”)), or unrated but determined by PIMCO to be of comparable quality. Bonds of below investment grade quality are regarded as having predominantly speculative characteristics with respect to capacity to pay interest and repay principal and are commonly referred to as “junk bonds.” Bonds in the lowest investment grade category may also be considered to possess some speculative characteristics by certain rating agencies. The Fund may also invest without limit in investment grade securities. The Fund generally expects to invest approximately 60% of its total assets in above investment grade securities and approximately 40% of its total assets in below investment grade securities, but may determine to allocate more heavily or exclusively to either category at any time and from time to time based on PIMCO’s economic outlook, market conditions, and other factors.

Independent credit analysis. PIMCO relies primarily on its own analysis of the credit quality and risks associated with individual municipal bonds and other municipal securities considered for the Fund, rather than relying exclusively on rating agencies or third-party research. The Fund’s portfolio managers utilize this information in an attempt to manage credit risk and to identify investments that are undervalued or that offer attractive yields relative to PIMCO’s assessment of their credit characteristics. This aspect of PIMCO’s capabilities will be particularly important to the extent that the Fund invests in high yield municipal bonds or other securities.

Duration management. The Fund does not target a specific duration or maturity for the municipal bonds and other securities in which it invests, and the Fund’s average portfolio duration, as calculated by PIMCO may vary significantly depending on market conditions and other factors. There is no limit on the maturity or duration of any individual security in which the Fund may invest. Duration is a measure used to determine the sensitivity of a security’s price to changes in interest rates. The longer a security’s duration, the more sensitive it will be to changes in interest rates. The portfolio managers focus on municipal bonds with the potential to offer attractive current income, typically looking for bonds that can provide consistently attractive current yields or that are trading at competitive market prices. Capital appreciation, if any, generally arises from decreases in interest rates or improving credit fundamentals for a particular state, municipality or issuer.

Portfolio Contents

April 30, 2021 (as supplemented May 14, 2021) | PROSPECTUS 2

PIMCO Flexible Municipal Income Fund

To the extent consistent with the applicable liquidity requirements for interval funds under Rule 23c-3 of the Investment Company Act of 1940, as amended (the “Act”), the Fund may invest without limit in illiquid investments.

Leverage

facilities. The Fund may also enter into transactions other than those noted above that may give rise to a form of leverage including, among others, futures and forward contracts (including foreign currency exchange contracts), total return swaps and other derivative transactions, loans of portfolio securities, short sales and when-issued, delayed delivery and forward commitment transactions.

The Fund utilizes certain kinds of leverage, including, without limitation, tender option bonds, opportunistically and may choose to increase or decrease, or eliminate entirely, its use of leverage over time and from time to time based on PIMCO’s assessment of the yield curve environment, interest rate trends, market conditions and other factors. The Fund may also determine to increase its leverage through the issuance of additional Preferred Shares, or decrease the leverage it currently maintains through its outstanding Preferred Shares through Preferred Share redemptions or tender offers and may or may not determine to replace such leverage. The Fund may issue additional Preferred Shares without the approval of holders of Common Shares (“Common Shareholders”). If the Fund issues additional Preferred Shares in the future, all costs and expenses relating to the issuance and ongoing maintenance of the Preferred Shares will be borne by the Common Shareholders, and these costs and expenses may be significant. The Fund’s net assets attributable to its Preferred Shares and the net proceeds the Fund obtains from the issuance of additional preferred shares or the use of tender option bonds or other forms of leverage will be invested in accordance with the Fund’s investment objectives and policies as described in this prospectus. So long as the rate of return, net of applicable Fund expenses, on the debt obligations and other investments purchased by the Fund exceeds the dividend rates payable on the Preferred Shares together with the costs to the Fund of other leverage it utilizes, the investment of the Fund’s assets attributable to leverage will generate more income than will be needed to pay the costs of the leverage. If so, and all other things being equal, the excess may be used to pay higher dividends to Common Shareholders than if the Fund were not so leveraged.

Under the Act, the Fund is not permitted to issue preferred shares unless, immediately after such issuance, the value of the Fund’s total net assets (as defined below) is at least 200% of the liquidation value of any outstanding Preferred Shares and the newly issued preferred shares plus the aggregate amount of any senior securities of the Fund representing indebtedness (i.e., such liquidation value plus the aggregate amount of senior securities representing indebtedness may not exceed 50% of the Fund’s total net assets). In addition, the Fund is not permitted to declare any cash dividend or other distribution on its Common Shares unless, at the time of such declaration, the value of the Fund’s total net assets satisfies the above-referenced 200% coverage requirement.

The Act also generally prohibits the Fund from engaging in most forms of leverage representing indebtedness (including the use of tender option bonds, to the extent that these instruments are not covered as described below), which does not include Preferred Shares, unless immediately after the issuance of the leverage the Fund has satisfied the asset coverage test with respect to senior securities representing

3 Prospectus | PIMCO Flexible Municipal Income Fund

Prospectus

indebtedness prescribed by the Act; that is, the value of the Fund’s total assets less all liabilities and indebtedness not represented by senior securities (for these purposes, “total net assets”) is at least 300% of the senior securities representing indebtedness (effectively limiting the use of leverage through senior securities representing indebtedness to 33 1/3% of the Fund’s total net assets, including assets attributable to such leverage). In addition, the Fund is not permitted to declare any cash dividend or other distribution on its Common Shares unless, at the time of such declaration, this asset coverage test is satisfied. The Fund may (but is not required to) cover its commitments under tender option bonds or other derivatives instruments by the segregation of liquid assets, or by entering into offsetting transactions or owning positions covering its obligations. To the extent that certain of these instruments are so covered, they will not be considered “senior securities” under the Act and therefore will not be subject to the Act 300% asset coverage requirement otherwise applicable to forms of senior securities representing indebtedness used by the Fund. However, such instruments, even if covered, represent a form of economic leverage and create special risks. The use of these forms of leverage increases the volatility of the Fund’s investment portfolio and could result in larger losses to Common Shareholders than if these strategies were not used. See “Principal Risks of the Fund—Leverage Risk.”

The Fund’s ability to utilize leverage is also limited by asset coverage requirements and other guidelines imposed by the terms of the Preferred Shares and are imposed by rating agencies that provide ratings for the Preferred Shares which are more restrictive than the limitations imposed by the Act noted above. Please see “Description of Capital Structure and Shares - Preferred Shares.”

Leveraging is a speculative technique and there are special risks and costs involved. The Fund cannot assure you that its use of Preferred Shares and any other forms of leverage (such as tender option bonds) will be successful or result in a higher yield on your Common Shares. When leverage is used, the net asset value of the Common Shares and the yield to Common Shareholders will be more volatile. In addition, dividends paid on Preferred Shares (including the Preferred Shareholder Gross-Up (as described below)) and interest and other expenses borne by the Fund with respect to its use of tender option bonds or other forms of leverage are borne by the Common Shareholders (and not by the holders of Preferred Shares (“Preferred Shareholders”)) and result in a reduction of the net asset value of the Common Shares. In addition, because the fees received by the Investment Manager are based on the total managed assets of the Fund, which includes total assets of the Fund (including assets attributable to any reverse repurchase agreements, dollar rolls, tender option bonds, borrowings and Preferred Shares that may be outstanding, if any), the Investment Manager has a financial incentive for the Fund to use certain forms of leverage (e.g., Preferred Shares and tender option bonds), which may create a conflict of interest between the Investment Manager, on the one hand, and the Common Shareholders, on the other hand.

Rule 18f-4 limits a fund’s derivatives exposure through a value-at-risk test and requires the adoption and implementation of a derivatives risk management program for certain derivatives users. Subject to certain conditions, limited derivatives users (as defined in Rule 18f-4), however, would not be subject to the full requirements of Rule 18f-4. In connection with the adoption of Rule 18f-4, the SEC also eliminated the asset segregation framework arising from prior SEC guidance for covering derivatives and certain financial instruments. Compliance with Rule 18f-4 will not be required until August 19, 2022. As the Fund comes into compliance, the Fund’s approach to asset segregation and coverage requirements described in this prospectus will be impacted. In addition, Rule 18f-4 could restrict the Fund’s ability to engage in certain derivatives transactions and/or increase the costs of such derivatives transactions, which could adversely affect the value or performance of the Fund and the Common Shares and/or the Fund’s distribution rate.

Please see “Use of Leverage,” “Principal Risks of the Fund—Leverage Risk” and “Principal Risks of the Fund—Segregation and Coverage Risk” for additional information regarding leverage and related risks.

Investment Manager

PIMCO serves as the Investment Manager for the Fund. Subject to the supervision of the Board of Trustees of the Fund, PIMCO is responsible for managing the investment activities of the Fund and the Fund’s business affairs and other administrative matters. David Hammer, Rachel Betton and Amit Arora are jointly and primarily responsible for the day-to-day management of the Fund.

PIMCO is located at 650 Newport Center Drive, Newport Beach, CA 92660. Organized in 1971, PIMCO provides investment management and advisory services to private accounts of institutional and individual clients and to registered investment companies. PIMCO is a majority-owned indirect subsidiary of Allianz SE, a publicly traded European insurance and financial services company. As of December 31, 2020, PIMCO had approximately $2.21 trillion in assets under management.

Fee Waiver Agreement. Pursuant to a Management Fee Waiver Agreement between the Fund and PIMCO, PIMCO has contractually agreed, through May 2, 2022, to waive 25% of the management fees it is entitled to receive from the Fund pursuant to the Investment Management Agreement (“Management Fee Waiver Agreement”). The Management Fee Waiver Agreement will continue through the date set forth above, at which time it will terminate unless otherwise agreed to in writing by the parties. See “Management of the Fund—Fee Waiver Agreement.”

Distributions

The Fund intends to distribute substantially all of its net investment income to shareholders in the form of dividends. The Fund intends to declare income dividends daily and distribute them monthly to shareholders of record. Distributions can only be made from net investment income after paying any accrued dividends to holders of the Preferred Shares. At least annually, the Fund also intends to distribute to you your pro rata share of any available net capital gain and taxable

April 30, 2021 (as supplemented May 14, 2021) | PROSPECTUS 4

PIMCO Flexible Municipal Income Fund

ordinary income, if any. Net short-term capital gains may be paid more frequently. The dividends that the Fund pays will depend on a number of factors, including dividends payable on any Preferred Shares issued by the Fund, including the Preferred Shareholder Gross-Up (as described below) (and expenses associated with other forms of leverage).

Although it does not currently intend to do so, the Board of Trustees may change the Fund’s dividend policy and the amount or timing of Fund distributions, based on a number of factors. Unless shareholders specify otherwise, dividends will be reinvested in Common Shares of the Fund in accordance with the Fund’s dividend reinvestment plan. The Fund may pay distributions from sources that may not be available in the future and that are unrelated to the Fund’s performance, such as from offering proceeds and/or borrowings. See “Distributions” and “Dividend Reinvestment Plan.”

The Fund’s Preferred Shares pay dividend distributions at a stated rate, which rate is based generally on the assumption that such dividend distributions will consist entirely of dividends that pass through the character of exempt interest earned by the Fund and are therefore not taxable to shareholders for regular federal income tax purposes (“exempt-interest dividends”). IRS rules nonetheless require a regulated investment company having two or more classes of stock for U.S. federal income tax purposes to characterize amounts distributed as dividends to each class for the taxable year in accordance with their pro rata share of income or gains of any type. Therefore, the Fund might be required to characterize a portion of dividends paid to Preferred Shareholders as ordinary income or capital gain dividends. The terms of such Preferred Shares provide further that, in the event less than the entire amount of any particular dividend distribution paid pursuant to the stated rate were to consist of “exempt-interest dividends” (i.e., if a portion of any particular dividend were to derive from ordinary income or capital gain, including short-term capital gain taxable as ordinary income when distributed), the amount of such dividend would increase by an amount (the “Preferred Shareholder Gross-Up”) such that the after-tax amount of such dividend, as increased by the Preferred Shareholder Gross-Up, would equal the total amount the holder of such Preferred Shares would have received if the dividend at the stated rate had consisted entirely of “exempt-interest dividends.” Any Preferred Shareholder Gross-Up would reduce the amount that would otherwise be distributable to Common Shareholders.

The Fund might not distribute all or a portion of any net capital gain for a taxable year. If the Fund does not distribute all of its net capital gain for a taxable year, it will pay federal income tax on the retained gain. Each Common Shareholder of record as of the end of the Fund’s taxable year will include in income for federal income tax purposes, as long-term capital gain, his or her share of the retained gain, will be deemed to have paid his or her proportionate share of the tax paid by the Fund on such retained gain, and will be entitled to an income tax credit or refund for that share of the tax. The Fund will treat the retained capital gain amount as a substitute for equivalent cash distributions. The Fund will send shareholders detailed tax information with respect to the Fund’s distributions annually. See “Tax Matters.”

Distributor, Custodian and Transfer Agent

PIMCO Investments LLC, an affiliate of PIMCO, serves as the Fund’s principal underwriter and distributor. State Street Bank and Trust Company serves as the primary custodian of the Fund’s assets and also provides certain fund accounting, sub-administrative and compliance services to the Fund on behalf of the Investment Manager. UMB Bank, n.a. serves as a custodian of the Fund for the purpose of processing investor subscriptions and repurchases. DST Systems, Inc. serves as the Fund’s transfer agent and dividend disbursement agent.

Unlisted Closed-End Fund Structure; Limited Liquidity

The Fund’s Common Shares are not listed for trading on any securities exchange. There is currently no secondary market for its Common Shares and the Fund does not expect any secondary market to develop for its Common Shares. Shareholders of the Fund are not able to have their Common Shares redeemed or otherwise sell their Common Shares on a daily basis because the Fund is an unlisted closed-end fund. In order to provide liquidity to shareholders, the Fund is structured as an “interval fund” and conducts periodic repurchase offers for a portion of its outstanding Common Shares, as described herein. Investors should consider Common Shares of the Fund to be an illiquid investment. An investment in the Fund is suitable only for long-term investors who can bear the risks associated with the limited liquidity of the Common Shares. Investors should consider their investment goals, time horizons and risk tolerance before investing in the Fund.

Investor Suitability

An investment in the Fund involves a considerable amount of risk. It is possible that you will lose money. An investment in the Fund is suitable only for investors who can bear the risks associated with the limited liquidity of the Common Shares and should be viewed as a long-term investment. Before making your investment decision, you should (i) consider the suitability of this investment with respect to your investment objectives and personal financial situation and (ii) consider factors such as your personal net worth, income, age, risk tolerance and liquidity needs. An investment in the Fund should not be viewed as a complete investment program.

Principal Risks of the Fund

Interest Rate Risk

Interest rate risk is the risk that fixed income securities and other instruments in the Fund’s portfolio will decline in value because of a change in interest rates. Interest rate changes can be sudden and unpredictable, and the Fund may lose money as a result of movements in interest rates. The Fund may not be able to effectively hedge against changes in interest rates or may choose not to do so for cost or other reasons.

A wide variety of factors can cause interest rates or yields of U.S. Treasury securities (or yields of other types of bonds) to rise (e.g., central bank monetary policies, inflation rates, general economic

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Prospectus

conditions, etc.). This is especially true under current conditions because interest rates and bond yields are at or near historically low levels, thus, the Fund currently faces a heightened level of interest rate risk.

In response to market volatility and economic uncertainty, the U.S. government and certain foreign central banks have taken steps to stabilize markets by, among other things, reducing interest rates. Interest rates in the United States and many parts of the world, including certain European countries, are at or near historically low levels, and a period of low interest rates could persist for a sustained period. Changing interest rates may have unpredictable effects on markets, may result in heightened market volatility and may detract from Fund performance.

Municipal Bond Risk

Investing in the municipal bond market involves the risks of investing in debt securities generally and certain other risks. The amount of public information available about the municipal bonds in which the Fund may invest is generally less than that for corporate equities or bonds, and the investment performance of the Fund’s investment in municipal bonds may therefore be more dependent on the analytical abilities of PIMCO than its investments in taxable bonds. The secondary market for municipal bonds also tends to be less well developed or liquid than many other securities markets, which may adversely affect the Fund’s ability to sell municipal bonds at attractive prices.

The ability of municipal issuers to make timely payments of interest and principal may be diminished during general economic downturns, by litigation, legislation or political events, or by the bankruptcy of the issuer. Laws, referenda, ordinances or regulations enacted in the future by Congress or state legislatures or the applicable governmental entity could extend the time for payment of principal and/or interest, or impose other constraints on enforcement of such obligations, or on the ability of municipal issuers to levy taxes. Issuers of municipal securities also might seek protection under the bankruptcy laws. In the event of bankruptcy of such an issuer, the Fund could experience delays in collecting principal and interest and the Fund may not, in all circumstances, be able to collect all principal and interest to which it is entitled. To enforce its rights in the event of a default in the payment of interest or repayment of principal, or both, the Fund may take possession of and manage the assets securing the issuer's obligations on such securities, which may increase the Fund's operating expenses. Adverse economic, business, legal or political developments might affect all or a substantial portion of the Fund’s municipal bonds in the same manner. The Fund will be particularly subject to these risks to the extent that it focuses its investments in municipal bonds in a particular state or geographic region.

be entitled to treat such interest as exempt from federal income tax. Certain tender option bonds may be less liquid or may become less liquid as a result of, among other things, a credit rating downgrade, a payment default or a disqualification from tax-exempt status. The Fund’s investment in the securities issued by a tender option bond trust may involve greater risk and volatility than an investment in a fixed rate bond, and the value of such securities may decrease significantly when market interest rates increase. Tender option bond trusts could be terminated due to market, credit or other events beyond the Fund’s control, which could require the Fund to dispose of portfolio investments at inopportune times and prices. The Fund may use a tender option bond program as a way of achieving leverage in its portfolio, in which case the Fund will be subject to leverage risk.

The Fund may invest in revenue bonds, which are typically issued to fund a wide variety of capital projects including electric, gas, water and sewer systems; highways, bridges and tunnels; port and airport facilities; colleges and universities; and hospitals. Because the principal security for a revenue bond is generally the net revenues derived from a particular facility or group of facilities or, in some cases, from the proceeds of a special excise or other specific revenue source, there is no guarantee that the particular project will generate enough revenue to pay its obligations, in which case the Fund’s performance may be adversely affected.

The Fund may invest in taxable municipal bonds, such as Build America Bonds. Build America Bonds are tax credit bonds created by the American Recovery and Reinvestment Act of 2009, which authorized state and local governments to issue Build America Bonds as taxable bonds in 2009 and 2010, without volume limitations, to finance any capital expenditures for which such issuers could otherwise issue traditional tax-exempt bonds. The Fund’s investments in Build America Bonds or similar taxable municipal bonds will result in taxable income and the Fund may elect to pass through to Common Shareholders the corresponding tax credits. The tax credits can generally be used to offset federal income taxes and the alternative minimum tax, but such credits are generally not refundable. Taxable municipal bonds involve similar risks as tax-exempt municipal bonds, including credit and market risk. See “Principal Risks of the Fund—Credit Risk” and “Principal Risks of the Fund—Market Risk.”

Municipal securities are also subject to interest rate, credit, and liquidity risk.

Interest Rate Risk. The value of municipal securities, similar to other fixed income securities, will likely drop as interest rates rise in the general market. Conversely, when rates decline, bond prices generally rise.

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may be most at risk. To the extent the Fund invests in lower quality or high yield municipal securities, it may be more sensitive to the adverse credit events in the municipal market. The treatment of municipalities in bankruptcy is more uncertain, and potentially more adverse to debt holders, than for corporate issues.

Liquidity Risk. The risk that investors may have difficulty finding a buyer when they seek to sell, and therefore, may be forced to sell at a discount to the market value. Liquidity may sometimes be impaired in the municipal market and because the Fund primarily invests in municipal securities, it may find it difficult to purchase or sell such securities at opportune times. Liquidity can be impaired due to interest rate concerns, credit events, or general supply and demand imbalances. Depending on the particular issuer and current economic conditions, municipal securities could be deemed more volatile investments.

In addition to general municipal market risks, different municipal sectors may face different risks.

Revenue bonds are secured by special tax revenues or other revenue sources. If the specified revenues do not materialize, then the bonds may not be repaid.

Private activity bonds are yet another type of municipal security. Municipalities use private activity bonds to finance the development of industrial facilities for use by private enterprise. Principal and interest payments are to be made by the private enterprise benefiting from the development, which means that the holder of the bond is exposed to the risk that the private issuer may default on the bond.

Moral obligation bonds are usually issued by special purpose public entities. If the public entity defaults, repayment becomes a “moral obligation” instead of a legal one. The lack of a legally enforceable right to payment in the event of default poses a special risk for a holder of the bond because it has little or no ability to seek recourse in the event of default.

In addition, a significant restructuring of federal income tax rates, such as the changes to federal income tax rates that occurred in 2017, or even serious discussion on the topic in Congress could cause municipal bond prices to fall. The demand for municipal securities is strongly influenced by the value of tax-exempt income to investors relative to taxable income. Lower income tax rates potentially reduce the advantage of owning municipal securities.

Similarly, changes to state or federal regulation tied to a specific sector, such as the hospital sector, could have an impact on the revenue stream for a given subset of the market.

Municipal notes are similar to general municipal debt obligations, but they generally possess shorter terms. Municipal notes can be used to provide interim financing and may not be repaid if anticipated revenues are not realized.

Puerto Rico-Specific Risk

Puerto Rico. Puerto Rico currently is experiencing significant fiscal and economic challenges, including substantial debt service obligations, high levels of unemployment, underfunded public retirement systems, and persistent government budget deficits. These challenges may negatively affect the value of the Fund’s investments in Puerto Rico municipal securities. Major ratings agencies have downgraded the general obligation debt of Puerto Rico to below investment grade and continue to maintain a negative outlook for this debt, which increases the likelihood that the rating will be lowered further. Further downgrades or defaults may place additional strain on the Puerto Rico economy and may negatively affect the value, liquidity, and volatility of the Fund’s investments in Puerto Rico municipal securities. Legislation, including legislation that would allow Puerto Rico to restructure its municipal debt obligations, thus increasing the risk that Puerto Rico may never pay off municipal indebtedness, or may pay only a small fraction of the amount owed, could also impact the value of the Fund’s investments in Puerto Rico municipal securities.

Municipal Project-Specific Risk

The Fund may be more sensitive to adverse economic, business or political developments if it invests a substantial portion of its assets in the bonds of specific projects (such as those relating to education, health care, housing, transportation, and utilities), industrial development bonds, or in general obligation bonds, particularly if there is a large concentration from issuers in a single state. This is because the value of municipal securities can be significantly affected by the political, economic, legal, and legislative realities of the particular issuer’s locality or municipal sector events. Similarly, changes to state or federal regulation tied to a specific sector, such as the hospital sector, could have an impact on the revenue stream for a given subset of the market.

California State-Specific Risk

The Fund may invest in municipal bonds issued by or on behalf of the State of California and its political subdivisions, financing authorities and their agencies, and therefore may be affected significantly by economic, regulatory or political developments affecting the ability of California issuers to pay interest or repay principal. Certain issuers of California municipal bonds have experienced serious financial difficulties in the past and reoccurrence of these difficulties may impair the ability of certain California issuers to pay principal or interest on their obligations. Provisions of the California Constitution and State statutes that limit the taxing and spending authority of California governmental entities may impair the ability of California issuers to pay principal and/or interest on their obligations. While California’s economy is broad, it does have major concentrations in advanced technology, aerospace and defense-related manufacturing, trade, entertainment, real estate and financial services, and may be sensitive to economic problems affecting those industries. Future California political and economic developments, constitutional amendments, legislative measures, executive orders, administrative regulations, litigation and voter initiatives could have an adverse effect on the debt obligations of California issuers.

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Prospectus

New York State-Specific Risk

The Fund may invest in municipal bonds issued by or on behalf of the State of New York and its political subdivisions, financing authorities and their agencies, and therefore may be affected significantly by economic, regulatory or political developments affecting the ability of New York issuers to pay interest or repay principal. While New York’s economy is broad, it does have concentrations in the financial services industry, and may be sensitive to economic problems affecting that industry. Certain issuers of New York municipal bonds experienced serious financial difficulties in the past and reoccurrence of these difficulties may impair the ability of certain New York issuers to pay principal or interest on their obligations. The financial health of New York City affects that of the State, and when New York City experiences financial difficulty it may have an adverse effect on New York municipal bonds held by the Fund. The growth rate of New York has at times been somewhat slower than the nation overall. The economic and financial condition of New York also may be affected by various financial, social, economic and political factors.

Insurance Risk

The Fund may purchase municipal securities that are secured by insurance, bank credit agreements or escrow accounts. The credit quality of the companies that provide such credit enhancements will affect the value of those securities. Certain significant providers of insurance for municipal securities have incurred significant losses as a result of exposure to sub-prime mortgages and other lower credit quality investments that have experienced recent defaults or otherwise suffered extreme credit deterioration. As a result, such losses have reduced the insurers’ capital and called into question their continued ability to perform their obligations under such insurance if they are called upon to do so in the future. The insurance feature of a municipal security does not guarantee the full payment of principal and interest through the life of an insured obligation, the market value of the insured obligation or the net asset value of the common shares represented by such insured obligation.

Inflation/Deflation Risk

Inflation risk is the risk that the value of assets or income from the Fund’s investments will be worth less in the future as inflation decreases the value of payments at future dates. As inflation increases, the real value of the Fund’s portfolio could decline. Deflation risk is the risk that prices throughout the economy decline over time. Deflation may have an adverse effect on the creditworthiness of issuers and may make issuer default more likely, which may result in a decline in the value of the Fund’s portfolio and Common Shares.

Call Risk

Call risk refers to the possibility that an issuer may exercise its right to redeem a fixed income security earlier than expected (a call). Issuers may call outstanding securities prior to their maturity for a number of reasons (e.g., declining interest rates, changes in credit spreads and improvements in the issuer’s credit quality). If an issuer calls a security in which the Fund has invested, the Fund may not recoup the full amount

of its initial investment and may be forced to reinvest in lower-yielding securities, securities with greater credit risks or securities with other, less favorable features.

Credit Risk

Issuer Risk

The value of a security may decline for a number of reasons that directly relate to the issuer, such as management performance, financial leverage and reduced demand for the issuer’s goods or services, as well as the historical and prospective earnings of the issuer and the value of its assets. A change in the financial condition of a single issuer may affect securities markets as a whole. These risks can apply to the Common Shares issued by the Fund and to the issuers of securities and other instruments in which the Fund invests.

Liquidity Risk

Fixed income securities with longer durations until maturity face heightened levels of liquidity risk as compared to fixed income securities with shorter durations until maturity. The risks associated with illiquid

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instruments may be particularly acute in situations in which the Fund’s operations require cash (such as in connection with repurchase offers) and could result in the

Fund borrowing to meet its short-term needs or incurring losses on the sale of illiquid instruments. See “Principal Risks of the Fund —Repurchase Offers Risk.” It may also be the case that other market participants may be attempting to liquidate fixed income holdings at the same time as the Fund, causing increased supply in the market and contributing to liquidity risk and downward pricing pressure. See “Principal Risks of the Fund—Valuation Risk.”

Repurchase Offers Risk

As described under “Periodic Repurchase Offers” above, the Fund is an “interval fund” and, in order to provide liquidity to shareholders, the Fund, subject to applicable law, intends to conduct quarterly repurchase offers of the Fund’s outstanding Common Shares at NAV, subject to approval of the Board. In each quarter, such repurchase offers will be for at least 5% of its outstanding Common Shares at NAV, pursuant to Rule 23c-3 under the Act.

The Fund currently expects to conduct quarterly repurchase offers for 10% of its outstanding Common Shares under ordinary circumstances. The Fund believes that these repurchase offers are generally beneficial to the Fund’s shareholders, and repurchases generally will be funded from available cash or sales of portfolio securities. However, repurchase offers and the need to fund repurchase obligations may affect the ability of the Fund to be fully invested or force the Fund to maintain a higher percentage of its assets in liquid investments, which may harm the Fund’s investment performance. Moreover, diminution in the size of the Fund through repurchases may result in untimely sales of portfolio securities (with associated imputed transaction costs, which may be significant), and may limit the ability of the Fund to participate in new investment opportunities or to achieve its investment objectives. The Fund may accumulate cash by holding back (i.e., not reinvesting) payments received in connection with the Fund’s investments. The Fund believes that payments received in connection with the Fund’s investments will generate sufficient cash to meet the maximum potential amount of the Fund’s repurchase obligations. If at any time cash and other liquid assets held by the Fund are not sufficient to meet the Fund’s repurchase obligations, the Fund intends, if necessary, to sell investments. If, as expected, the Fund employs investment leverage, repurchases of Common Shares would compound the adverse effects of leverage in a declining market. In addition, if the Fund borrows to finance repurchases, interest on that borrowing will negatively affect Common Shareholders who do not tender their Common Shares by increasing the Fund’s expenses and reducing any net investment income. If a repurchase offer is oversubscribed, the Fund may, but is not required to, determine to increase the amount repurchased by up to 2% of the Fund’s outstanding shares as of the date of the Repurchase Request Deadline. In the event that the Fund determines not to repurchase more than the repurchase offer amount, or if shareholders tender more than the repurchase offer amount plus 2% of the Fund’s outstanding shares as of the date of the Repurchase Request Deadline, the Fund will repurchase the Common Shares tendered on a pro rata

basis, and shareholders will have to wait until the next repurchase offer to make another repurchase request. As a result, shareholders may be unable to liquidate all or a given percentage of their investment in the Fund during a particular repurchase offer. Some shareholders, in anticipation of proration, may tender more Common Shares than they wish to have repurchased in a particular quarter, thereby increasing the likelihood that proration will occur. A shareholder may be subject to market and other risks, and the NAV of Common Shares tendered in a repurchase offer may decline between the Repurchase Request Deadline and the date on which the NAV for tendered Common Shares is determined. In addition, the repurchase of Common Shares by the Fund may be a taxable event to shareholders.

High Yield Securities Risk

To the extent that the Fund invests in high yield securities and unrated securities of similar credit quality (commonly known as “high yield securities” or “junk bonds”), the Fund may be subject to greater levels of credit risk, call risk and liquidity risk than funds that do not invest in such securities, which could have a negative effect on the NAV of the Fund’s Common Shares or Common Share dividends. These securities are considered predominantly speculative with respect to an issuer’s continuing ability to make principal and interest payments, and may be more volatile than other types of securities. An economic downturn or individual corporate developments could adversely affect the market for these securities and reduce the Fund’s ability to sell these securities at an advantageous time or price. The Fund may purchase distressed securities that are in default or the issuers of which are in bankruptcy, which involve heightened risks.

Issuers of high yield securities may have the right to “call” or redeem the issue prior to maturity, which may result in the Fund having to reinvest the proceeds in other high yield securities or similar instruments that may pay lower interest rates. The Fund may also be subject to greater levels of liquidity risk than funds that do not invest in high yield securities. Consequently, transactions in high yield securities may involve greater costs than transactions in more actively traded securities. These factors may result in the Fund being unable to realize full value for these securities and/or may result in the Fund not receiving the proceeds from a sale of a high yield security for an extended period after such sale, each of which could result in losses to the Fund. Because of the risks involved in investing in high yield securities, an investment in the Fund should be considered speculative.

To the extent the Fund focuses on below investment grade debt obligations, PIMCO’s capabilities in analyzing credit quality and associated risks will be particularly important, and there can be no assurance that PIMCO will be successful in this regard. See “The Fund’s Investment Objectives and Strategies—Portfolio Contents—High Yield Securities” for additional information.

Due to the risks involved in investing in high yield securities, an investment in the Fund should be considered speculative. The Fund’s credit quality policies apply only at the time a security is purchased, and the Fund is not required to dispose of a security in the event that a rating agency or PIMCO downgrades its assessment of the credit

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Prospectus

characteristics of a particular issue. In determining whether to retain or sell such a security, PIMCO may consider factors including, but not limited to, PIMCO’s assessment of the credit quality of the issuer of such security, the price at which such security could be sold and the rating, if any, assigned to such security by other rating agencies. Analysis of creditworthiness may be more complex for issuers of high yield securities than for issuers of higher quality debt securities.

Market Risk

The market price of securities owned by the Fund may go up or down, sometimes rapidly or unpredictably. Securities may decline in value due to factors affecting securities markets generally or particular industries represented in the securities markets. The value of a security may decline due to general market conditions which are not specifically related to a particular company, such as real or perceived adverse economic conditions, changes in the general outlook for corporate earnings, changes in interest or currency rates, adverse changes to credit markets or adverse investor sentiment generally. The value of a security may also decline due to factors which affect a particular industry or industries, such as labor shortages or increased production costs and competitive conditions within an industry. During a general downturn in the securities markets, multiple asset classes may decline in value simultaneously. Equity securities generally have greater price volatility than fixed income securities. Credit ratings downgrades may also negatively affect securities held by the Fund. Even when markets perform well, there is no assurance that the investments held by the Fund will increase in value along with the broader market.

In addition, market risk includes the risk that geopolitical and other events will disrupt the economy on a national or global level. For instance, war, terrorism, market manipulation, government defaults, government shutdowns, political changes or diplomatic developments, public health emergencies (such as the spread of infectious diseases, pandemics and epidemics) and natural/environmental disasters can all negatively impact the securities markets, which could cause the Fund to lose value. These events could reduce consumer demand or economic output, result in market closures, travel restrictions or quarantines, and significantly adversely impact the economy. The current contentious domestic political environment, as well as political and diplomatic events within the United States and abroad, such as presidential elections in the U.S. or abroad or the U.S. government’s inability at times to agree on a long-term budget and deficit reduction plan, has in the past resulted, and may in the future result, in a government shutdown or otherwise adversely affect the U.S. regulatory landscape, the general market environment and/or investor sentiment, which could have an adverse impact on the Fund’s investments and operations. Additional and/or prolonged U.S. federal government shutdowns may affect investor and consumer confidence and may adversely impact financial markets and the broader economy, perhaps suddenly and to a significant degree. Governmental and quasi-governmental authorities and regulators throughout the world have previously responded to serious economic disruptions with a variety of significant fiscal and monetary policy changes, including but not limited to, direct capital infusions into companies, new monetary programs and dramatically

lower interest rates. An unexpected or sudden reversal of these policies, or the ineffectiveness of these policies, could increase volatility in securities markets, which could adversely affect the Fund’s investments. Any market disruptions could also prevent the Fund from executing advantageous investment decisions in a timely manner. Funds that have focused their investments in a region enduring geopolitical market disruption will face higher risks of loss, although the increasing interconnectivity between global economies and financial markets can lead to events or conditions in one country, region or financial market adversely impacting a different country, region or financial market. Thus, investors should closely monitor current market conditions to determine whether the Fund meets their individual financial needs and tolerance for risk.

Current market conditions may pose heightened risks with respect to the Fund’s investment in fixed income securities. As discussed more under “Principal Risks of the Fund—Interest Rate Risk,” interest rates in the U.S. are at or near historically low levels. Any interest rate increases in the future could cause the value of the Fund to decrease. As such, fixed income securities markets may experience heightened levels of interest rate, volatility and liquidity risk.

Exchanges and securities markets may close early, close late or issue trading halts on specific securities or generally, which may result in, among other things, the Fund being unable to buy or sell certain securities or financial instruments at an advantageous time or accurately price its portfolio investments.

Municipal Bond Market Risk. The amount of public information available about the municipal bonds in the Fund’s portfolio is generally less than that for corporate equities or bonds, and the investment performance of the Fund may therefore be more dependent on the analytical abilities of PIMCO than would be a stock fund or taxable bond fund. The secondary market for municipal bonds, particularly below investment grade bonds in which the Fund may invest, also tends to be less well-developed and less liquid than many other securities markets, which may adversely affect the Fund’s ability to sell its bonds at attractive prices.

Management Risk

The Fund is subject to management risk because it is an actively managed investment portfolio. PIMCO and each individual portfolio manager will apply investment techniques and risk analysis in making investment decisions for the Fund, but there can be no guarantee that these decisions will produce the desired results. Certain securities or other instruments in which the Fund seeks to invest may not be available in the quantities desired. In addition, regulatory restrictions, actual or potential conflicts of interest or other considerations may cause PIMCO to restrict or prohibit participation in certain investments. In such circumstances, PIMCO or the individual portfolio managers may determine to purchase other securities or instruments as substitutes. Such substitute securities or instruments may not perform as intended, which could result in losses to the Fund. To the extent the Fund employs strategies targeting perceived pricing inefficiencies, arbitrage strategies

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or similar strategies, it is subject to the risk that the pricing or valuation of the securities and instruments involved in such strategies may change unexpectedly, which may result in reduced returns or losses to the Fund. The Fund is also subject to the risk that deficiencies in the internal systems or controls of PIMCO or another service provider will cause losses for the Fund or hinder Fund operations. For example, trading delays or errors (both human and systematic) could prevent the Fund from purchasing a security expected to appreciate in value. Additionally, actual or potential conflicts of interest, legislative, regulatory, or tax restrictions, policies or developments may affect the investment techniques available to PIMCO and each individual portfolio manager in connection with managing the Fund and may also adversely affect the ability of the Fund to achieve its investment objectives. There also can be no assurance that all of the personnel of PIMCO will continue to be associated with PIMCO for any length of time. The loss of the services of one or more key employees of PIMCO could have an adverse impact on the Fund’s ability to realize its investment objectives.

In addition, the Fund may rely on various third-party sources to calculate its NAV. As a result, the Fund is subject to certain operational risks associated with reliance on service providers and service providers’ data sources. In particular, errors or systems failures and other technological issues may adversely impact the Fund’s calculations of its NAV, and such NAV calculation issues may result in inaccurately calculated NAVs, delays in NAV calculation and/or the inability to calculate NAVs over extended periods. The Fund may be unable to recover any losses associated with such failures.

Reinvestment Risk

Income from the Fund’s portfolio will decline if and when the Fund invests the proceeds from matured, traded or called debt obligations at market interest rates that are below the portfolio’s current earnings rate. For instance, during periods of declining interest rates, an issuer of debt obligations may exercise an option to redeem securities prior to maturity, forcing the Fund to invest in lower-yielding securities. The Fund also may choose to sell higher yielding portfolio securities and to purchase lower yielding securities to achieve greater portfolio diversification, because the portfolio managers believe the current holdings are overvalued or for other investment-related reasons. A decline in income received by the Fund from its investments is likely to have a negative effect on dividend levels, NAV and/or overall return of the Common Shares.

Leverage Risk

The Fund’s use of leverage (as described under “Use of Leverage” in the body of this prospectus) creates the opportunity for increased Common Share net income, but also creates special risks for Common Shareholders. To the extent used, there is no assurance that the Fund’s leveraging strategies will be successful. Leverage is a speculative technique that may expose the Fund to greater risk and increased costs. The Fund’s assets attributable to any outstanding Preferred Shares or the net proceeds that the Fund obtains from its use of tender option bonds, derivatives or other forms of leverage, if any, will be invested in accordance with the Fund’s investment objectives and policies as

described in this prospectus. Dividends payable with respect to any Preferred Shares outstanding and interest expense payable by the Fund with respect to any tender option bonds, derivatives and other forms of leverage will generally be based on shorter-term interest rates that would be periodically reset. If shorter-term interest rates rise relative to the rate of return on the Fund’s portfolio, the interest and other costs to the Fund of leverage (including interest expenses on tender option bonds and the dividend rate on any outstanding Preferred Shares, including the Preferred Shareholder Gross-Up) could exceed the rate of return on the debt obligations and other investments held by the Fund, thereby reducing return to Common Shareholders. In addition, fees and expenses of any form of leverage used by the Fund will be borne entirely by the Common Shareholders (and not by Preferred Shareholders, if any) and will reduce the investment return of the Common Shares. Therefore, there can be no assurance that the Fund’s use of leverage will result in a higher yield on the Common Shares, and it may result in losses. In addition, any Preferred Shares issued by the Fund are expected to pay cumulative dividends, which may tend to increase leverage risk.

Leverage creates several major types of risks for Common Shareholders, including:

■

the likelihood of greater volatility of NAV of Common Shares, and of the investment return to Common Shareholders, than a comparable portfolio without leverage;

■

the possibility either that Common Share dividends will fall if the interest and other costs of leverage rise, or that dividends paid on Common Shares will fluctuate because such costs vary over time; and

■

the effects of leverage in a declining market or a rising interest rate environment, as leverage is likely to cause a greater decline in the NAV of the Common Shares than if the Fund were not leveraged.

In addition, the counterparties to the Fund’s leveraging transactions and any Preferred Shareholders of the Fund will have complete priority over the Fund’s Common Shareholders in the distribution of the Fund’s assets.

In addition to tender option bonds and Preferred Shares, the Fund may engage in other transactions that may give rise to a form of leverage including, among others loans of portfolio securities, short sales and when-issued, delayed delivery and forward commitment transactions, credit default swaps, reverse repurchases, or other derivatives. The Fund’s use of such transactions gives rise to associated leverage risks described above, and may adversely affect the Fund’s income, distributions and total returns to Common Shareholders. Under current regulatory requirements, the Fund manages some of its derivative positions by segregating an amount of cash or liquid securities equal to the notional value or the market value, as applicable, of those positions. See “Principal Risks of the Fund—Segregation and Coverage Risk.” The Fund may also offset derivatives positions against one another or against other assets to manage effective market exposure resulting from derivatives in its portfolio. To the extent that any offsetting positions do

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not behave in relation to one another as expected, the Fund may perform as if it is leveraged through use of these derivative strategies. See “Use of Leverage.”

The Fund is required to satisfy certain asset coverage requirements in connection with its use of Preferred Shares, including those imposed by regulatory and rating agency requirements. Accordingly, any decline in the net asset value of the Fund’s investments could result in the risk that the Fund will fail to meet its asset coverage requirements for any such Preferred Shares or the risk of the Preferred Shares being downgraded by a rating agency. In an extreme case, the Fund’s current investment income might not be sufficient to meet the dividend requirements on any Preferred Shares outstanding. In order to address these types of events, the Fund might need to liquidate investments in order to fund a redemption of some or all of Preferred Shares. Liquidation at times of adverse economic conditions may result in a loss to the Fund. At other times, these liquidations may result in gain at the Fund level and thus in additional taxable distributions to Common Shareholders. See “Tax Matters” for more information. Any Preferred Shares, tender option bonds, loans of portfolio securities, short sales and when-issued, delayed delivery and forward commitment transactions, credit default swaps, reverse repurchases, or other derivatives by the Fund or counterparties to the Fund’s other leveraging transactions, if any, would have, seniority over the Fund’s Common Shares.

When the Fund issues Preferred Shares, the Fund pays (and the Common Shareholders bear) all costs and expenses relating to the issuance and ongoing maintenance of Preferred Shares. In addition, holders of any Preferred Shares issued by the Fund would have complete priority over Common Shareholders in the distribution of the Fund’s assets. Furthermore, Preferred Shareholders, voting separately as a single class, have the right to elect two members of the Board at all times and to elect a majority of the trustees in the event two full years’ dividends on the Preferred Shares are unpaid, and also have separate class voting rights on certain matters. Accordingly, Preferred Shareholders may have interests that differ from those of Common Shareholders, and may at times have disproportionate influence over the Fund’s affairs.

Because the fees received by the Investment Manager are based on the average daily “total managed assets” of the Fund, which includes total assets of the Fund (including assets attributable to any reverse repurchase agreements, dollar rolls, tender option bonds, borrowings and Preferred Shares that may be outstanding, if any), the Investment Manager has a financial incentive for the Fund to use certain forms of leverage (e.g., Preferred Shares and tender option bonds), which may create a conflict of interest between the Investment Manager, on the one hand, and the Common Shareholders, on the other hand.

Segregation and Coverage Risks

Fund’s assets or otherwise cover its obligations. To avoid having these instruments considered senior securities, the Fund may segregate liquid assets with a value equal (on a daily mark-to-market basis) to its obligations under these types of leveraged transactions, enter into offsetting transactions or otherwise cover such transactions. At times, all or a substantial portion of the Fund’s liquid assets may be segregated for purposes of various portfolio transactions. The Fund may be unable to use such segregated assets for certain other purposes, which could result in the Fund earning a lower return on its portfolio than it might otherwise earn if it did not have to segregate those assets in respect of, or otherwise cover, such portfolio positions. To the extent the Fund’s assets are segregated or committed as cover, it could limit the Fund’s investment flexibility. Segregating assets and covering positions will not limit or offset losses on related positions. In connection with the adoption of Rule 18f-4, the SEC also eliminated the asset segregation framework arising from prior SEC guidance for covering derivatives and certain financial instruments (as described under “Use of Leverage” in the body of this prospectus).

In addition, the Fund is required to satisfy various additional asset coverage requirements with respect to its Preferred Shares. See “Description of Capital Structure and Shares — Preferred Shares.”

Derivatives Risk

The Fund may, but is not required to, utilize a variety of derivative instruments (both long and short positions) for investment or risk management purposes. Derivatives are financial contracts whose value depends on, or is derived from, the value of an underlying asset, reference rate or index. The Fund may use derivatives to gain exposure to securities markets in which it may invest (e.g., pending investment of the proceeds of this offering in individual securities, as well as on an ongoing basis). The Fund may also use derivatives to add leverage to its portfolio. See “Principal Risks of the Fund—Leverage Risk.” Derivatives transactions that the Fund may utilize include, but are not limited to, purchases or sales of futures and forward contracts (including foreign currency exchange contracts), call and put options, credit default swaps, total return swaps, basis swaps and other swap agreements. The Fund may also have exposure to derivatives, such as interest rate or credit-default swaps, through investment in credit-linked trust certificates and other securities issued by special purpose or structured vehicles. The Fund may also use derivatives for leverage, in which case their use would involve leveraging risk, and in some cases, may subject the Fund to the potential for unlimited loss. The use of derivatives may cause the Fund’s investment returns to be impacted by the performance of securities the Fund does not own and result in the Fund’s total investment exposure exceeding the value of its portfolio.

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PIMCO Flexible Municipal Income Fund

Fund—Segregation and Coverage Risk.” They also involve the risk of improper valuation, the risk of unfavorable or ambiguous documentation and the risk that changes in the value of a derivative instrument may not correlate perfectly with the underlying asset, rate or index. The Fund’s use of derivatives may increase or accelerate the amount of taxes payable by Common Shareholders. See “Tax Matters.”

Over-the-counter (“OTC”) derivatives are also subject to the risk that a counterparty to the transaction will not fulfill its contractual obligations to the other party, as many of the protections afforded to centrally-cleared derivative transactions might not be available for OTC derivatives. The primary credit risk on derivatives that are exchange-traded or traded through a central clearing counterparty resides with the Fund’s clearing broker or the clearinghouse itself.

Participation in the markets for derivative instruments involves investment risks and transaction costs to which the Fund may not be subject absent the use of these strategies. It may not be possible for the Fund to modify, terminate, or offset the Fund’s obligations or the Fund’s exposure to the risks associated with a derivative transaction prior to its scheduled termination or maturity date, which may create a possibility of increased volatility and/or decreased liquidity to the Fund.

Because the markets for certain derivative instruments (including markets located in foreign countries) are relatively new and still developing, appropriate derivative transactions may not be available in all circumstances for risk management or other purposes. Upon the expiration of a particular contract, the Fund may wish to retain the Fund’s position in the derivative instrument by entering into a similar contract, but may be unable to do so if the counterparty to the original contract is unwilling to enter into the new contract and no other appropriate counterparty can be found. When such markets are unavailable, the Fund will be subject to increased liquidity and investment risk.

When a derivative is used as a hedge against a position that the Fund holds, any loss generated by the derivative generally should be substantially offset by gains on the hedged investment, and vice versa. Hedges are sometimes subject to imperfect matching between the derivative and the underlying instrument, and there can be no assurance that the Fund’s hedging transactions will be effective. In such case, the Fund may lose money.

The regulation of the derivatives markets has increased over the past several years, and additional future regulation of the derivatives markets may make derivatives more costly, may limit the availability or reduce the liquidity of derivatives, or may otherwise adversely affect the value or performance of derivatives. Any such adverse future developments could impair the effectiveness or raise the costs of the Fund’s derivative transactions, impede the employment of the Fund’s derivatives strategies, or adversely affect the Fund’s performance.

Valuation Risk

determined in good faith pursuant to policies and procedures approved by the Board of Trustees. See “Net Asset Value.” Fair value pricing may require subjective determinations about the value of a security or other asset. As a result, there can be no assurance that fair value pricing will result in adjustments to the prices of securities or other assets, or that fair value pricing will reflect actual market value, and it is possible that the fair value determined for a security or other asset will be materially different from quoted or published prices, from the prices used by others for the same security or other asset and/or from the value that actually could be or is realized upon the sale of that security or other asset.

Counterparty Risk

The Fund will be subject to credit risk with respect to the counterparties to the derivative contracts and other instruments entered into by the Fund or held by special purpose or structured vehicles in which the Fund invests. In the event that the Fund enters into a derivative transaction with a counterparty that subsequently becomes insolvent or becomes the subject of a bankruptcy case, the derivative transaction may be terminated in accordance with its terms and the Fund’s ability to realize its rights under the derivative instrument and its ability to distribute the proceeds could be adversely affected. If a counterparty becomes bankrupt or otherwise fails to perform its obligations under a derivative contract due to financial difficulties, the Fund may experience significant delays in obtaining any recovery (including recovery of any collateral it has provided to the counterparty) in a dissolution, assignment for the benefit of creditors, liquidation, winding-up, bankruptcy, or other analogous proceeding. In addition, in the event of the insolvency of a counterparty to a derivative transaction, the derivative transaction would typically be terminated at its fair market value. If the Fund is owed this fair market value in the termination of the derivative transaction and its claim is unsecured, the Fund will be treated as a general creditor of such counterparty, and will not have any claim with respect to any underlying security or asset. The Fund may obtain only a limited recovery or may obtain no recovery in such circumstances. While the Fund may seek to manage its counterparty risk by transacting with a number of counterparties, concerns about the solvency of, or a default by, one large market participant could lead to significant impairment of liquidity and other adverse consequences for other counterparties.

Confidential Information Access Risk

In managing the Fund, PIMCO may from time to time have the opportunity to receive material, non-public information (“Confidential Information”) about the issuers of certain investments, including, without limitation, senior floating rate loans, other loans and related investments being considered for acquisition by the Fund or held in the Fund’s portfolio. Pursuant to applicable policies and procedures, PIMCO may (but is not required to) seek to avoid receipt of Confidential Information about such issuers so as to avoid possible restrictions on its ability to purchase and sell investments on behalf of the Fund and other clients to which such Confidential Information relates. In such circumstances, the Fund (and other PIMCO clients) may be disadvantaged in comparison to other investors, including with respect to the price the Fund pays or receives when it buys or sells an

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investment. Further, PIMCO’s and the Fund’s abilities to assess the desirability of proposed consents, waivers or amendments with respect to certain investments may be compromised if they are not privy to available Confidential Information. PIMCO may also determine to receive such Confidential Information in certain circumstances under its applicable policies and procedures. If PIMCO intentionally or unintentionally comes into possession of Confidential Information, it may be unable, potentially for a substantial period of time, to purchase or sell investments to which such Confidential Information relates.

Private Placements Risk

A private placement involves the sale of securities that have not been registered under the 1933 Act, or relevant provisions of applicable non-U.S. law, to certain institutional and qualified individual purchasers, such as the Fund. In addition to the general risks to which all securities are subject, securities received in a private placement generally are subject to strict restrictions on resale, and there may be no liquid secondary market or ready purchaser for such securities. See “Principal Risks of the Fund—Liquidity Risk.” Therefore, the Fund may be unable to dispose of such securities when it desires to do so, or at the most favorable time or price. Private placements may also raise valuation risks. See “Principal Risks of the Fund—Valuation Risk.”

Risk of Regulatory Changes

Financial entities, such as investment companies and investment advisers, are generally subject to extensive government regulation and intervention. Government regulation and/or intervention may change the way the Fund is regulated, affect the expenses incurred directly by the Fund and the value of its investments, and limit and/or preclude the Fund’s ability to achieve its investment objectives. Government regulation may change frequently and may have significant adverse consequences. The Fund and the Investment Manager have historically been eligible for exemptions from certain regulations. However, there is no assurance that the Fund and the Investment Manager will continue to be eligible for such exemptions.

Moreover, government regulation may have unpredictable and unintended effects. Legislative or regulatory actions to address perceived liquidity or other issues in fixed income markets generally, or in particular markets such as the municipal securities market, may alter or impair the Fund’s ability to pursue its investment objectives or utilize certain investment strategies and techniques.

is intended to replace U.S. dollar LIBOR and measures the cost of overnight borrowings through repurchase agreement transactions collateralized with U.S. Treasury securities). Any potential effects of the transition away from LIBOR on the Fund or on certain instruments in which the Fund invests can be difficult to ascertain, and they may vary depending on factors that include, but are not limited to: (i) existing fallback or termination provisions in individual contracts and (ii) whether, how, and when industry participants develop and adopt new reference rates and fallbacks for both legacy and new products and instruments. The transition may also result in a reduction in the value of certain instruments held by the Fund, a change in the cost of borrowing or the dividend rate for any preferred shares that may be issued by the Fund, or a reduction in the effectiveness of related Fund transactions such as hedges. Any such effects of the transition away from LIBOR, as well as other unforeseen effects, could result in losses to the Fund.

Other Investment Companies Risk

The Fund may invest up to 5% of its total assets in securities of other investment companies, including closed-end funds, exchange-traded funds and other open-end funds, that invest primarily in municipal bonds and other municipal securities of the types in which the Fund may invest directly. As a shareholder in an investment company, the Fund will bear its ratable share of that investment company’s expenses, and would remain subject to payment of the Fund’s investment management fees with respect to the assets so invested. Common Shareholders would therefore be subject to duplicative expenses to the extent the Fund invests in other investment companies. In addition, these other investment companies may utilize leverage, in which case an investment would subject the Fund to additional risks associated with leverage. Due to its own financial interest or other business considerations, the Investment Manager may choose to invest a portion of the Fund’s assets in investment companies sponsored or managed by the Investment Manager or its related parties in lieu of investments by the Fund directly in portfolio securities, or may choose to invest in such investment companies over investment companies sponsored or managed by others. Applicable law may limit the Fund’s ability to invest in other investment companies. See “Principal Risks of the Fund—Leverage Risk.”

Tax Risk

The Fund has elected to be treated as a “regulated investment company” under the Code and intends each year to qualify and be eligible to be treated as such, so that it generally will not be subject to U.S. federal income tax on its net investment income or net short-term or long-term capital gains that it timely distributes (or is deemed to distribute, as described below) to shareholders. In order to qualify for such treatment, the Fund must meet certain asset diversification tests and at least 90% of its gross income for such year must be certain types of qualifying income. If for any taxable year the Fund were to fail to meet the income or diversification test described above, the Fund could in some cases cure such failure, including by paying a Fund-level tax and, in the case of a diversification test failure, disposing of certain assets.

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PIMCO Flexible Municipal Income Fund

If, in any year, the Fund were to fail to qualify for treatment as a regulated investment company under the Code, and were ineligible to or did not otherwise cure such failure, the Fund would be subject to tax on its taxable income at corporate rates and, when such income is distributed, shareholders would be subject to further tax on such distributions to the extent of the Fund’s current or accumulated earnings and profits.

To qualify to pay exempt-interest dividends, which are treated as items of interest excludable from gross income for regular federal income tax purposes, at least 50% of the value of the total assets of the Fund must consist of obligations the interest on which is exempt from regular federal income tax under section 103(a) of the Code as of the close of each quarter of the Fund’s taxable year. If the proportion of taxable investments held by the Fund exceeds 50% of the Fund’s total assets as of the close of any quarter of the Fund’s taxable year, the Fund will not for that taxable year satisfy the general eligibility test that otherwise permits it to pay exempt-interest dividends.

The value of the Fund’s investments and its net asset value may be adversely affected by changes in tax rates and policies. Because interest income from municipal securities is normally not subject to regular federal income taxation, the attractiveness of municipal securities in relation to other investment alternatives is affected by changes in federal income tax rates or changes in the tax-exempt status of interest income from municipal securities. Any proposed or actual changes in such rates or exempt status, therefore, can significantly affect the demand for and supply, liquidity and marketability of municipal securities. This could in turn affect the Fund’s net asset value and ability to acquire and dispose of municipal securities at desirable yield and price levels. Additionally, the Fund is not a suitable investment for individual retirement accounts, for other tax-exempt or tax-deferred accounts or for investors who are not sensitive to the federal income tax consequences of their investments.

Potential Conflicts of Interest Risk—Allocation of Investment Opportunities

The Investment Manager is involved worldwide with a broad spectrum of financial services and asset management activities and may engage in the ordinary course of business in activities in which its interests or the interests of its clients may conflict with those of the Fund. The Investment Manager may provide investment management services to other funds and discretionary managed accounts that follow an investment program similar to that of the Fund. Subject to the requirements of the Act, the Investment Manager intends to engage in such activities and may receive compensation from third parties for its services. The results of the Fund’s investment activities may differ from those of the Fund’s affiliates, or another account managed by the Fund’s affiliates, and it is possible that the

Fund could sustain losses during periods in which one or more of the Fund’s affiliates and/or other accounts achieve profits on their trading for proprietary or other accounts. The Investment Manager has adopted policies and procedures reasonably designed to allocate investment opportunities on a fair and equitable basis over time.

Distribution Risk

Although the Fund may seek to maintain a level distribution rate, the Fund’s distribution rate may be affected by numerous factors, including but not limited to changes in realized and projected market returns, fluctuations in market interest rates, Fund performance, and other factors. For instance, during periods of low or declining interest rates, the Fund’s distributable income and dividend levels may decline for many reasons. There can be no assurance that a change in market conditions or other factors will not result in a change in the Fund’s distribution rate or that the rate will be sustainable in the future.

Securities Lending Risk

For the purpose of achieving income, the Fund may lend its portfolio securities to brokers, dealers, and other financial institutions provided a number of conditions are satisfied, including that the loan is fully collateralized. Please see “Investment Objectives and Policies—Loans of Portfolio Securities” in the Statement of Additional Information for more details. When the Fund lends portfolio securities, its investment performance will continue to reflect changes in the value of the securities loaned, and the Fund will also receive a fee or interest on the collateral. Securities lending involves the risk of loss of rights in the collateral or delay in recovery of the collateral if the borrower fails to return the security loaned or becomes insolvent. The Fund may pay lending fees to a party arranging the loan, which may be an affiliate of the Fund. Cash collateral received by the Fund in securities lending transactions may be invested in short-term liquid fixed income instruments or in money market or short-term mutual funds, or similar investment vehicles, including affiliated money market or short-term mutual funds. The Fund bears the risk of such investments.

Portfolio Turnover Risk

The Investment Manager manages the Fund without regard generally to restrictions on portfolio turnover. The use of futures contracts and other derivative instruments with relatively short maturities may tend to exaggerate the portfolio turnover rate for the Fund. Trading in fixed income securities does not generally involve the payment of brokerage commissions, but does involve indirect transaction costs. The use of futures contracts and other derivative instruments may involve the payment of commissions to futures commission merchants or other intermediaries. Higher portfolio turnover involves correspondingly greater expenses to the Fund, including brokerage commissions or dealer mark-ups and other transaction costs on the sale of securities and reinvestments in other securities. The higher the rate of portfolio turnover of the Fund, the higher these transaction costs borne by the Fund generally will be. Such sales may result in realization of taxable capital gains (including short-term capital gains, which are generally taxed to shareholders at ordinary income tax rates when distributed net of short-term capital losses and net long-term capital losses), and may adversely impact the Fund’s after-tax returns. See “Tax Matters.”

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Operational Risk

An investment in the Fund, like any fund, can involve operational risks arising from factors such as processing errors, human errors, inadequate or failed internal or external processes, failures in systems and technology, changes in personnel and errors caused by third-party service providers. The occurrence of any of these failures, errors or breaches could result in a loss of information, regulatory scrutiny, reputational damage or other events, any of which could have a significant adverse effect on the Fund. While the Fund seeks to minimize such events through controls and oversight, there may still be failures that could cause losses to the Fund.

Market Disruptions Risk

The Fund is subject to investment and operational risks associated with financial, economic and other global market developments and disruptions, including those arising from war, terrorism, market manipulation, government interventions, defaults and shutdowns, political changes or diplomatic developments, public health emergencies (such as the spread of infectious diseases, pandemics and epidemics) and natural/environmental disasters, which can all negatively impact the securities markets, interest rates, auctions, secondary trading, ratings, credit risk, inflation, deflation and other factors relating to the Fund’s investments or the Investment Manager’s operations and cause the Fund to lose value. These events can also impair the technology and other operational systems upon which the Fund’s service providers, including PIMCO as the Fund’s investment adviser, rely, and could otherwise disrupt the Fund’s service providers’ ability to fulfill their obligations to the Fund.

The U.S. Federal Reserve has made emergency interest-rate cuts, moving short-term rates to near zero, issued forward guidance that rates will remain low until the economy weathers the COVID-19 crisis, and resumed quantitative easing. Additionally, Congress has approved stimulus to offset the severity and duration of the adverse economic effects of COVID-19 and related disruptions in economic and business activity. Dozens of central banks across Europe, Asia, and elsewhere have announced and/or adopted similar economic relief packages. The introduction and adoption of these packages could cause market disruptions and volatility. In addition, the end of any such program could cause market downturns, disruptions and volatility, particularly if markets view the ending as premature.

Cyber Security Risk

Cyber security failures or breaches may result in financial losses to the Fund and its shareholders. These failures or breaches may also result in disruptions to business operations, potentially resulting in financial losses; interference with the Fund’s ability to calculate its NAV, process shareholder transactions or otherwise transact business with shareholders; impediments to trading; violations of applicable privacy and other laws; regulatory fines; penalties; reputational damage; reimbursement or other compensation costs; additional compliance and cyber security risk management costs and other adverse consequences. In addition, substantial costs may be incurred in an attempt to prevent any cyber incidents in the future. There is also a risk that cyber security breaches may not be detected. The Fund and its shareholders could be negatively impacted as a result.

Non-Diversification Risk

The Fund is “non-diversified,” which means that the Fund may invest a greater percentage of its assets in the securities of a single issuer (such as bonds issued by a particular state) than funds that are “diversified.” A fund that invests in a relatively small number of issuers is more susceptible to risks associated with a single economic, political or regulatory occurrence than a more diversified portfolio might be. Similarly, the Fund may be subject to increased economic, business or political risk to the extent that it invests a substantial portion of its assets in a particular currency, in a group of related industries, in a particular issuer, in the bonds of similar projects or in a narrowly defined geographic area outside the U.S. Notwithstanding the Fund’s status as a “non-diversified” investment company under the Act, the Fund intends to qualify as a regulated investment company accorded special tax treatment under the Code, which imposes its own diversification requirements.

Certain Affiliations

Certain broker-dealers may be considered to be affiliated persons of the Fund and/or the Investment Manager due to their possible affiliations with Allianz SE, the ultimate parent of the Investment Manager. Absent an exemption from the SEC or other regulatory relief, the Fund is generally precluded from effecting certain principal transactions with affiliated brokers, and its ability to purchase securities being underwritten by an affiliated broker or a syndicate including an affiliated broker, or to utilize affiliated brokers for agency transactions, is subject to restrictions. This could limit the Fund’s ability to engage in securities transactions and take advantage of market opportunities.

Anti-Takeover Provisions

The Fund’s Amended and Restated Agreement and Declaration of Trust (the “Declaration”) includes provisions that could limit the ability of other entities or persons to acquire control of the Fund or to convert the Fund to open-end status. See “Anti-Takeover and Other Provisions in the Declaration of Trust.”

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Summary of Fund Expenses

This table is intended to assist investors in understanding the various costs and expenses directly or indirectly associated with investing in the Fund. You may qualify for sales charge discounts on Class A-2 Common Shares of the Fund if you and your family invest, or agree to invest in the future, in a certain amount of Class A-1, Class A-2, Class A-3 and/or Class A-4 common shares of the Fund (to the extent available) or other eligible closed-end interval funds that are sponsored by PIMCO. More information about these and other discounts is available in the “Plan of Distribution—Share Classes” section on page 54 of this prospectus, Appendix B to this prospectus (Financial Firm-Specific Sales Charge Waivers and Discounts) or from your financial advisor.

Shareholder Transaction Expenses (fees paid directly from your investment):

	Institutional Class	Class A-1	Class A-2	Class A-3
Maximum Initial Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	None(1)	None(1)	3.00%	None(1)
Maximum Early Withdrawal Charge (Load) (as a percentage of the lower of the original purchase price or repurchase price)	None	None	1.00%	None
Dividend Reinvestment Fees	None	None	None	None

While neither the Fund nor the Distributor impose an initial sales charge, if you buy Institutional Class, Class A-1 or Class A-3 Common Shares through certain financial firms, they may directly charge you transaction or other fees in such amount as they may determine. Please consult your financial firm for additional information.

Annual Fund Operating Expenses (as a percentage of Net Assets Attributable to Common Shares (reflecting leverage attributable to Preferred Shares and tender option bonds representing approximately 21.34% and 3.29%, respectively, of the Fund’s total managed assets)):

	Institutional Class	Class A-1	Class A-2	Class A-3
Management Fees(1)	1.12%	1.12%	1.12%	1.12%
Distribution and/or Service (12b-1) Fees	N/A	0.50%	0.50%	0.75%
Interest Payments on Borrowed Funds(2)(3)	0.04%	0.04%	0.04%	0.04%
Dividend and Other Costs on Preferred Shares(3)	0.69%	0.69%	0.69%	0.69%
Other Expenses(4)	0.11%	0.11%	0.11%	0.11%
Acquired Fund Fees and Expenses (Underlying Fund Expenses)(5)	0.05%	0.05%	0.05%	0.05%
Total Annual Fund Operating Expenses	2.01%	2.51%	2.51%	2.76%
Fee Waiver and/or Expense Reimbursement(6)(7)	(0.29%)	(0.29%)	(0.29%)	(0.29%)
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	1.72%	2.22%	2.22%	2.47%

Management fees include fees payable to the Investment Manager for advisory services and for supervisory, administrative and other services. The Fund pays for the advisory, supervisory and administrative services it requires under what is essentially an all-in fee structure (the “unified management fee”). Pursuant to an investment management agreement, PIMCO is paid a Management Fee of 0.75% of the Fund’s

total managed assets. The Fund (and not PIMCO) is responsible for certain fees and expenses, which are reflected in the table above, that are not covered by the unified management fee under the investment management agreement. Please see “Management of the Fund - Investment Management Agreement” for an explanation of the unified management fee and definition of “total managed assets.”

“Interest Payments on Borrowed Funds” and “Dividend and Other Costs on Preferred Shares” are borne by the Fund separately from the management fees paid to PIMCO. Excluding such expenses, Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement are 0.99%, 1.49%, 1.49% and 1.74% for Institutional Class, Class A-1, Class A-2 and Class A-3 shares, respectively.

“Interest Payments on Borrowed Funds” reflects the Fund's use of leverage in the form of tender option bonds as of December 31, 2020, which represented 3.29% of the Fund's total managed assets, at an annual interest rate cost to the Fund of 0.90%, which is based on market conditions as of that date. The actual amount of borrowing expenses borne by the Fund will vary over time in accordance with the level of the Fund's use of tender option bonds and/or other forms of borrowings and variations in market interest rates. Borrowing expense is required to be treated as an expense of the Fund for accounting purposes. Any associated income or gains (or losses) realized from leverage obtained through such instruments is not reflected in the Annual Expenses table above, but would be reflected in the Fund's performance results. “Dividends and Other Costs on Preferred Shares” reflects the Fund's outstanding Preferred Shares as of December 31, 2020 which represented 21.34% of the Fund's total managed assets (including the liquidation preference of outstanding Preferred Shares and assets attributable to tender option bond) as of that date, at an annual dividend cost to the Fund of 1.15%, which is based on market conditions as of that date, and including the amortization of Preferred Share offering costs of $1,645,314 over the three-year term of the Preferred Shares).The actual dividend rate paid on the Preferred Shares will vary over time in accordance with variations in market interest rates. See “Use of Leverage” and “Description of Capital Structure.” Dividend and Other Costs on Preferred Shares are borne directly by the Fund and reflected in the Fund's financial statement; however, the information presented in the table will differ from that presented in the Fund's Financial Highlights.

“Other Expenses” are based on estimated amounts for the current fiscal year.

Acquired Fund Fees and Expenses are based on the expense ratios of the other investment companies in which the Fund invests, which may change substantially over time and, therefore, significantly affect the Acquired Fund Fees and Expenses. Acquired Fund Fees and Expenses are borne directly by the Fund, but they will not be reflected in the Fund’s financial statements; and the information presented in the table will differ from that presented in the Fund’s financial highlights.

PIMCO has contractually agreed, through May 2, 2022, to waive 25% of its Management Fee for the Fund (the “Management Fee Waiver Agreement”). PIMCO may not seek reimbursement from the Fund with respect to the Management Fees waived pursuant to the Management Fee Waiver Agreement. The Management Fee Waiver Agreement will continue through May 2, 2022, at which time it will terminate unless otherwise agreed to in writing by the parties. In addition, the Management Fee Waiver Agreement will terminate upon termination of the Investment Management Agreement, or it may be terminated by the Fund, without payment of any penalty, upon notice to PIMCO at its principal place of business.

PIMCO has contractually agreed, through May 2, 2022, to waive its management fee, or reimburse the Fund, to the extent that organizational expenses and pro rata Trustees’ fees exceed 0.10% of the Fund’s net assets (the “Expense Limit”). Under an expense limitation agreement, in any month in which the investment management agreement is in effect, PIMCO is entitled to reimbursement by the Fund of any portion of the management fee reduced as set forth above (the “Reimbursement Amount”) during the previous thirty-six months, provided that such amount paid to PIMCO will not (1) together with any recoupment of organizational expenses, pro rata share of expenses related to obtaining or maintaining a Legal Entity Identifier and pro rata trustee fees or management fees exceed 0.10% of average net assets; (2) exceed the total Reimbursement Amount; or (3) include any amounts previously reimbursed to PIMCO. For the avoidance of doubt, any reimbursement of PIMCO’s management fee pursuant to the expense limitation agreement plus any recoupment of organizational expenses, pro rata share of expenses related to obtaining or maintaining a Legal Entity Identifier and pro rata Trustees’ fees will not exceed the lesser of (i) the expense limit in

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PIMCO Flexible Municipal Income Fund

effect at the time of waiver or reimbursement and (ii) the expense limit in effect at the time of recoupment. This expense limitation agreement will automatically renew for one-year terms unless PIMCO provides written notice to the Fund at least 30 days prior to the end of the then current term.

Example

As required by relevant SEC regulations, the following example illustrates the expenses (including any applicable sales charge) that you would pay on a $1,000 investment in the Common Shares, assuming a 5% annual return(1):

If you redeem your shares at the end of each period:

	1 Year	3 Years	5 Years	10 Years
Institutional Class	$17	$60	$106	$231
Class A-1	$23	$75	$131	$282
Class A-2	$62	$103	$157	$304
Class A-3	$25	$83	$143	$307

If you do not redeem your shares:

	1 Year	3 Years	5 Years	10 Years
Class A-2	$52	$103	$157	$304

The example above should not be considered a representation of future expenses. Actual expenses may be higher or lower than those shown. The example assumes that the estimated Interest Payments on Borrowed Funds, Dividend and Other Costs on Preferred Shares and Other Expenses set forth in the Annual Expenses table are accurate, that the Total Annual Fund Operating Expenses (as described above) remain the same for all periods shown, and that all dividends and distributions are reinvested at NAV. Actual expenses may be greater or less than those assumed. Moreover, the Fund’s actual rate of return may be greater or less than the hypothetical 5% annual return shown in the example. In addition to the fees and expenses described above, you may also be required to pay transaction or other fees on purchases of Institutional Class, Class A-1, Class A-2 or Class A-3 Common Shares of the Fund, which are not reflected in the example.

18 Prospectus | PIMCO Flexible Municipal Income Fund

PIMCO Flexible Municipal Income Fund

Financial Highlights

The financial highlights table set forth below is intended to help you understand the Fund’s recent financial performance. Information shown reflects performance of the Fund’s Institutional Class, Class A-1, Class A-2 and Class A-3 Common Shares. The information in the table below is for the fiscal year ended December 31, 2020 and the fiscal period ended December 31, 2019, audited by PricewaterhouseCoopers LLP (“PwC”), whose report on such financial statements is contained in the Fund’s December 31, 2020 annual report and is incorporated by reference into the Statement of Additional Information.

		Investment Operations			Less Distributions(c)

Selected Per Share Data for the Year or Period Ended^:	Net Asset Value Beginning of Year or Period(a)	Net Investment Income (Loss)(b)	Net Realized/ Unrealized Gain	Total	From Net Investment Income	From Net Realized Capital Gains	Tax Basis Return of Capital	Total
Institutional Class
12/31/2020	$10.74	$0.33	$0.72	$1.05	$(0.33)	$(0.01)	$0.00	$(0.34)
03/15/2019 - 12/31/2019	10.00	0.28	0.78	1.06	(0.28)	(0.04)	0.00	(0.32)
Class A-1
05/26/2020 - 12/31/2020	$10.30	$0.19	$1.17	$1.36	$(0.20)	$(0.01)	$0.00	$(0.21)
Class A-2
10/02/2020 - 12/31/2020	$10.96	$0.07	$0.50	$0.57	$(0.07)	$(0.01)	$0.00	$(0.08)
Class A-3
12/31/2020	$10.74	$0.26	$0.71	$0.97	$(0.25)	$(0.01)	$0.00	$(0.26)
09/10/2019 - 12/31/2019	10.76	0.08	0.02	0.10	(0.08)	(0.04)	0.00	(0.12)

A zero balance may reflect actual amounts rounding to less than $0.01 or 0.01%.

Annualized.

(a)

Includes adjustments required by U.S. GAAP and may differ from net asset values and performance reported elsewhere by the Fund.

(b)

Per share amounts based on average number of shares outstanding during the year or period.

(c)

The tax characterization of distributions is determined in accordance with Federal income tax regulations. See Note 2, Distributions—Common Shares, in the Notes to Financial Statements in the Annual Report for more information.

(d)

Ratio includes interest expense which primarily relates to participation in borrowing and financing transactions, dividends paid to VMTP and RVMTP shareholders and the amortization of debt issuance costs of these Preferred Shares. See Note 5, Borrowings and Other Financing Transactions and Note 13, Preferred Shares in the Notes to Financial Statements for more information.

19 Prospectus | PIMCO Flexible Municipal Income Fund

Prospectus

The Fund

The Fund is a non-diversified, closed-end management investment company registered under the Act. The Fund continuously offers its Common Shares and is operated as an “interval fund.” The Fund currently has four separate classes of Common Shares: Institutional Class, Class A-1, Class A-2 and Class A-3. The Fund was organized as a Massachusetts business trust on November 20, 2017, pursuant to a Declaration of Trust (the “Declaration of Trust”), which is governed by the laws of The Commonwealth of Massachusetts. The Fund commenced operations on March 15, 2019, in connection with its initial public offering of Institutional Class Common Shares. The Fund’s principal office is located at 1633 Broadway, New York, New York 10019.

Use of Proceeds

The Fund will invest the proceeds of the continuous offering of Common Shares on an ongoing basis in accordance with its investment objectives and policies as stated below. It is currently anticipated that the Fund will be able to invest all or substantially all of the net proceeds according to its investment objectives and policies within approximately three months after receipt of the proceeds, depending on the amount and timing of proceeds available to the Fund as well as the availability of investments consistent with the Fund’s investment objectives and policies, and except to the extent proceeds are held in cash to pay dividends or expenses, satisfy repurchase offers or for temporary defensive purposes. Pending such investment, it is anticipated that the proceeds of an offering will be invested in high quality, short-term, municipal or other tax-exempt securities, although the Fund may, if necessary, also invest in other high-quality, short-term securities.

The Fund’s Investment Objectives and Strategies

Investment Objectives

The Fund seeks to provide high current income exempt from federal income tax. Capital appreciation is a secondary objective. The types of securities and instruments in which the Fund may invest are summarized under “The Fund’s Investment Objectives and Policies—Portfolio Management Strategies—Portfolio Contents.”

Portfolio Management Strategies

PIMCO serves as the Investment Manager of the Fund and manages the Fund’s portfolio. See “Management of the Fund.” The portfolio management strategies and techniques to be utilized by PIMCO are described below.

Flexible Allocation Strategy. The Fund seeks to achieve its investment objectives by utilizing a flexible, multi-sector tax-efficient approach to investing, under normal circumstances, primarily in municipal bonds and other municipal securities that carry interest payments that are exempt from federal income tax. The principal issuers of these securities are state and local governments and their agencies located in any of the fifty states, as well as in Puerto Rico and other U.S. territories and possessions. To a lesser extent, the Fund also expects

to invest in a full range of preferred securities, with an emphasis on preferred securities that, at the time of issuance, are eligible to pay dividends that qualify for certain favorable federal income tax treatment. With PIMCO’s macroeconomic analysis as the basis for top-down investment decisions, the Fund seeks to offer investors an actively-managed municipal bond portfolio that aims to capitalize on what PIMCO believes are attractive opportunities across states and sectors within the U.S. municipal market.

PIMCO attempts to preserve and enhance the value of the Fund’s holdings relative to the municipal bond market, generally, using proprietary analytical models that test and evaluate the sensitivity of those holdings to changes in interest rates and yield relationships. There is no guarantee that PIMCO’s investment selection techniques will produce the desired results.

Credit quality. The Fund may invest without limit in municipal bonds and other securities of any credit quality, including without limitation, in securities that are, at the time of purchase, rated below investment grade (below Baa3 by Moody’s or below BBB- by either S&P or Fitch, or unrated but determined by PIMCO to be of comparable quality). Bonds of below investment grade quality are regarded as having predominantly speculative characteristics with respect to capacity to pay interest and repay principal and are commonly referred to as “junk bonds.” Bonds in the lowest investment grade category may also be considered to possess some speculative characteristics by certain rating agencies. The Fund may also invest without limit in investment grade securities. The Fund generally expects to invest approximately 60% of its total assets in above investment grade securities and approximately 40% of its total assets in below investment grade securities, but may determine to allocate more heavily or exclusively to either category at any time and from time to time based on PIMCO’s economic outlook, market conditions, and other factors.

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PIMCO Flexible Municipal Income Fund

other factors. There is no limit on the maturity or duration of any individual security in which the Fund may invest. Duration is a measure used to determine the sensitivity of a security’s price to changes in interest rates. The longer a security’s duration, the more sensitive it will be to changes in interest rates. The portfolio managers focus on municipal bonds with the potential to offer attractive current income, typically looking for bonds that can provide consistently attractive current yields or that are trading at competitive market prices. Capital appreciation, if any, generally arises from decreases in interest rates or improving credit fundamentals for a particular state, municipality or issuer.

Portfolio Contents and Other Information

Investment Parameters

The Fund will invest, under normal circumstances, at least 80% of its net assets (plus any borrowings for investment purposes) in a portfolio of municipal bonds and other municipal securities, the interest from which, in the opinion of bond counsel for the issuer at the time of issuance (or on the basis of other authority believed by PIMCO to be reliable), is exempt from federal income tax (i.e., excluded from gross income for federal income tax purposes but not necessarily exempt from the federal alternative minimum tax or from the income taxes of any state or local government). The Fund’s 80% policy is a fundamental policy, which may not be changed without the approval of the holders of a majority of the Fund’s outstanding Common Shares and Preferred Shares voting together as a single class, and of the holders of a majority of the outstanding Preferred Shares voting as a separate class. A “majority of the outstanding” shares (whether voting together as a single class or voting as a separate class) means (i) 67% or more of such shares present at a meeting, if the holders of more than 50% of those shares are present or represented by proxy, or (ii) more than 50% of such shares, whichever is less. See “Description of Capital Structure and Shares—Preferred Shares—Voting Rights” for additional information with respect to the voting rights of holders of Preferred Shares.

Subject to the Fund’s investment policies described above, the Fund may invest in other securities, including securities eligible for resale under Rule 144A of the 1933 Act, and other privately placed securities, and other debt securities subject to federal income tax, including privately negotiated debt obligations with respect to which the principal and/or interest is determined by reference to the performance of a benchmark asset, market or interest rate (an “embedded index”), such as specific securities, an index of securities or specified interest rates, or the differential performance of two assets or markets, such as indexes reflecting bonds. The rate of interest on an income-producing security may be fixed, floating or variable. The Fund may also engage in credit spread trades. A credit spread trade is an investment position relating to a difference in the prices or interest rates of two bonds or other securities, in which the value of the investment position is determined by changes in the difference between the prices or interest rates, as the case may be, of the respective securities. The Fund may purchase and sell securities on a when-issued, delayed delivery or forward commitment basis and may engage in short sales. The Fund may invest in trust certificates issued in tender option bond programs. In these programs, a trust typically issues two classes of certificates and uses the proceeds to purchase municipal securities having relatively long maturities and bearing interest at a fixed interest rate substantially higher than prevailing short-term tax-exempt rates. The Fund may also invest up to 5% of its total assets in securities of other investment companies, including closed-end funds, exchange-traded funds and other open-end funds, that invest primarily in municipal bonds and other municipal securities of the types in which the Fund may invest directly.

The Fund may, but is not required to, invest in derivative instruments, such as options, futures and forward contracts or swap agreements. For purposes of the Fund’s 80% policy, the Fund values its derivative instruments based on their market value. The Fund may, without limitation, seek to obtain market exposure to the securities in which it primarily invests by entering into a series of purchase and sale contracts or by using other investment techniques (such as buy backs or dollar rolls).

To the extent consistent with the applicable liquidity requirements for interval funds under Rule 23c-3 of the Act, the Fund may invest without limit in illiquid investments.

Temporary defensive investments. In attempting to respond to adverse market, economic, political, or other conditions, as determined by PIMCO, the Fund may, for temporary defensive purposes, deviate from its investment strategy by investing some or all of its total assets in investments such as high grade debt securities, including high quality, short-term debt securities, and cash and cash equivalents. The Fund may not achieve its investment objectives when it does so.

The following provides additional information regarding the types of securities and other instruments in which the Fund will ordinarily invest. A more detailed discussion of these and other instruments and

23 Prospectus | PIMCO Flexible Municipal Income Fund

Prospectus

investment techniques that may be used by the Fund is provided under “Investment Objectives and Policies” in the Statement of Additional Information.

Municipal Bonds

Municipal bonds share the attributes of debt/fixed income securities in general, but are generally issued by states, municipalities and other political subdivisions, agencies, authorities and instrumentalities of states and multi-state agencies or authorities, and may be either taxable or tax-exempt instruments. The municipal bonds that the Fund may purchase include without limit general obligation bonds and limited obligation bonds (or revenue bonds), including industrial development bonds issued pursuant to former federal tax law. General obligation bonds are obligations involving the credit of an issuer possessing taxing power and are payable from such issuer’s general revenues and not from any particular source. Limited obligation bonds are payable only from the revenues derived from a particular facility or class of facilities or, in some cases, from the proceeds of a special excise or other specific revenue source. Tax-exempt private activity bonds and industrial development bonds generally are also limited obligation bonds and thus are not payable from the issuer’s general revenues. The credit and quality of private activity bonds and industrial development bonds are usually related to the credit of the corporate user of the facilities. Payment of interest on and repayment of principal of such bonds is the responsibility of the corporate user (and/or any guarantor). The secondary market for municipal bonds, particularly the lower rate bonds, also tends to be less well-developed and less liquid than many other securities markets, which may adversely affect the ability of the Fund to sell its bond at attractive prices or value municipal bonds.

The Fund may invest in Build America Bonds, which are tax credit bonds created by the American Recovery and Reinvestment Act of 2009, which authorized state and local governments to issue Build America Bonds as taxable bonds in 2009 and 2010, without volume limitations, to finance any capital expenditures for which such issuers could otherwise issue traditional tax-exempt bonds. State and local governments may receive a direct federal subsidy payment for a portion of their borrowing costs on Build America Bonds equal to 35% of the total coupon interest paid to investors. The state or local government issuer can elect to either take the federal subsidy or pass the 35% tax credit along to bondholders. The Fund’s investments in Build America Bonds will result in taxable income and the Fund may elect to pass through to shareholders the corresponding tax credits. The tax credits can generally be used to offset federal income taxes and the alternative minimum tax, but such credits are generally not refundable. Build America Bonds involve similar risks as municipal bonds, including credit and market risk. They are intended to assist state and local governments in financing capital projects at lower borrowing costs and are likely to attract a broader group of investors than tax-exempt municipal bonds. For example, taxable funds, such as the Fund, may choose to invest in Build America Bonds. Although Build America Bonds were only authorized for issuance during 2009 and 2010, the program may have resulted in reduced issuance of tax-exempt municipal bonds during the same period. The Build America Bond program expired on December 31, 2010, at which point no further

issuance of new Build America Bonds was permitted. As of the date of this prospectus, there is no indication that Congress will renew the program to permit issuance of new Build America Bonds.

The Fund may invest in pre-refunded municipal bonds. Pre-refunded municipal bonds are bonds that have been refunded to a call date prior to the final maturity of principal, or, in the case of pre-refunded municipal bonds commonly referred to as “escrowed-to-maturity bonds,” to the final maturity of principal, and remain outstanding in the municipal market. The payment of principal and interest of the pre-refunded municipal bonds held by the Fund is funded from securities in a designated escrow account that holds U.S. Treasury securities or other obligations of the U.S. Government (including its agencies and instrumentalities (“Agency Securities”)). Interest payments on pre-refunded bonds issued on or prior to December 31, 2017 are exempt from federal income tax; pre-refunded bonds issued after December 31, 2017 will not qualify for such tax-advantaged treatment. Pre-refunded bonds usually will bear an AAA/Aaa rating (if a re-rating has been requested and paid for) because they are backed by U.S. Treasury securities or Agency Securities. Because the payment of principal and interest is generated from securities held in an escrow account established by the municipality and an independent escrow agent, the pledge of the municipality has been fulfilled and the original pledge of revenue by the municipality is no longer in place. The escrow account securities pledged to pay the principal and interest of the pre-refunded municipal bond do not guarantee the price movement of the bond before maturity. Issuers of municipal bonds refund in advance of maturity the outstanding higher cost debt and issue new, lower cost debt, placing the proceeds of the lower cost issuance into an escrow account to pre-refund the older, higher cost debt. Investment in pre-refunded municipal bonds held by the Fund may subject the Fund to interest rate risk and market risk. In addition, while a secondary market exists for pre-refunded municipal bonds, if the Fund sells pre-refunded municipal bonds prior to maturity, the price received may be more or less than the original cost, depending on market conditions at the time of sale.

The Fund may invest in municipal lease obligations. A lease is not a full faith and credit obligation of the issuer and is usually backed only by the borrowing government’s unsecured pledge to make annual appropriations for lease payments. There have been challenges to the legality of lease financing in numerous states, and, from time to time, certain municipalities have considered not appropriating money for lease payments. In deciding whether to purchase a lease obligation for the Fund, PIMCO will assess the financial condition of the borrower, the merits of the project, the level of public support for the project and the legislative history of lease financing in the state. These securities may be less readily marketable than other municipal securities.

Some longer-term municipal bonds give the investor the right to “put” or sell the security at par (face value) within a specified number of days following the investor’s request—usually one to seven days. This demand feature enhances a security’s liquidity by shortening its effective

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PIMCO Flexible Municipal Income Fund

maturity and enables it to trade at a price equal to or very close to par. If a demand feature terminates prior to being exercised, the Fund would hold the longer-term security, which could experience substantially more volatility.

The Fund may invest in municipal warrants, which are essentially call options on municipal bonds. In exchange for a premium, municipal warrants give the purchaser the right, but not the obligation, to purchase a municipal bond in the future. The Fund may purchase a warrant to lock in forward supply in an environment in which the current issuance of bonds is sharply reduced. Like options, warrants may expire worthless and may have reduced liquidity.

The Fund may invest in municipal bonds with credit enhancements such as letters of credit, municipal bond insurance and standby bond purchase agreements (“SBPAs”). Letters of credit are issued by a third party, usually a bank, to enhance liquidity and to ensure repayment of principal and any accrued interest if the underlying municipal bond should default. Municipal bond insurance, which is usually purchased by the bond issuer from a private, nongovernmental insurance company, provides an unconditional and irrevocable guarantee that the insured bond’s principal and interest will be paid when due. Insurance does not guarantee the price of the bond. The credit rating of an insured bond reflects the credit rating of the insurer, based on its claims-paying ability. The obligation of a municipal bond insurance company to pay a claim extends over the life of each insured bond. Although defaults on insured municipal bonds have been low to date and municipal bond insurers have met their claims, there is no assurance that this will continue. A higher-than expected default rate could strain the insurer’s loss reserves and adversely affect its ability to pay claims to bondholders. Because a significant portion of insured municipal bonds that have been issued and are outstanding is insured by a small number of insurance companies, not all of which have the highest credit rating, an event involving one or more of these insurance companies, such as a credit rating downgrade, could have a significant adverse effect on the value of the municipal bonds insured by such insurance company or companies and on the municipal bond markets as a whole. An SBPA is a liquidity facility provided to pay the purchase price of bonds that cannot be re-marketed. The obligation of the liquidity provider (usually a bank) is only to advance funds to purchase tendered bonds that cannot be re-marketed and does not cover principal or interest under any other circumstances. The liquidity provider’s obligations under the SBPA are usually subject to numerous conditions, including the continued creditworthiness of the underlying borrower.

Tender Option Bonds. The Fund may invest in trust certificates issued in tender option bond programs. In a tender option bond transaction (“TOB”), a tender option bond trust (“TOB Trust”) issues floating rate certificates (“TOB Floater”) and residual interest certificates (“TOB Residual”) and utilizes the proceeds of such issuance to purchase a fixed-rate municipal bond (“Fixed Rate Bond”) that either is owned or identified by the Fund. The TOB Floater is generally issued to third party investors (typically a money market fund) and the TOB Residual is generally issued to the Fund, which sold or identified the Fixed Rate Bond. The TOB Trust divides the income stream provided by

the Fixed Rate Bond to create two securities, the TOB Floater, which is a short-term security, and the TOB Residual, which is a longer-term security. The interest rates payable on the TOB Residual issued to the Fund bear an inverse relationship to the interest rate on the TOB Floater. The interest rate on the TOB Floater is reset by a remarketing process typically every 7 to 35 days. After income is paid on the TOB Floater at current rates, the residual income from the Fixed Rate Bond goes to the TOB Residual. Therefore, rising short-term rates result in lower income for the TOB Residual, and vice versa. In the case of a TOB Trust that utilizes the cash received (less transaction expenses) from the issuance of the TOB Floater and TOB Residual to purchase the Fixed Rate Bond from the Fund, the Fund may then invest the cash received in additional securities, generating leverage for the Fund. Other PIMCO-managed accounts may also contribute municipal bonds to a TOB Trust into which the Fund has contributed Fixed Rate Bonds. If multiple PIMCO-managed accounts participate in the same TOB Trust, the economic rights and obligations under the TOB Residual will be shared among the funds ratably in proportion to their participation in the TOB Trust.

The TOB Residual may be more volatile and less liquid than other municipal bonds of comparable maturity. In most circumstances the TOB Residual holder bears substantially all of the underlying Fixed Rate Bond’s downside investment risk and also benefits from any appreciation in the value of the underlying Fixed Rate Bond. Investments in a TOB Residual typically will involve greater risk than investments in Fixed Rate Bonds.

A TOB Residual held by the Fund provides the Fund with the right to: (1) cause the holders of the TOB Floater to tender their notes at par, and (2) cause the sale of the Fixed Rate Bond held by the TOB Trust, thereby collapsing the TOB Trust. TOB Trusts are generally supported by a liquidity facility provided by a third party bank or other financial institution (the “Liquidity Provider”) that provides for the purchase of TOB Floaters that cannot be remarketed. The holders of the TOB Floaters have the right to tender their certificates in exchange for payment of par plus accrued interest on a periodic basis (typically weekly) or on the occurrence of certain mandatory tender events. The tendered TOB Floaters are remarketed by a remarketing agent, which is typically an affiliated entity of the Liquidity Provider. If the TOB Floaters cannot be remarketed, the TOB Floaters are purchased by the TOB Trust either from the proceeds of a loan from the Liquidity Provider or from a liquidation of the Fixed Rate Bond.

The TOB Trust may also be collapsed without the consent of the Fund, as the TOB Residual holder, upon the occurrence of certain “tender option termination events” (or “TOTEs”) as defined in the TOB Trust agreements. Such termination events typically include the bankruptcy or default of the municipal bond, a substantial downgrade in credit quality of the municipal bond, or a judgment or ruling that interest on the Fixed Rate Bond is subject to federal income taxation. Upon the occurrence of a termination event, the TOB Trust would generally be liquidated in full with the proceeds typically applied first to any accrued fees owed to the trustee, remarketing agent and liquidity provider, and then to the holders of the TOB Floater up to par plus accrued interest owed on the TOB Floater and a portion of gain share, if any, with the balance paid

25 Prospectus | PIMCO Flexible Municipal Income Fund

Prospectus

out to the TOB Residual holder. In the case of a mandatory termination event (“MTE”), after the payment of fees, the TOB Floater holders would be paid before the TOB Residual holders (i.e., the Fund). In contrast, in the case of a TOTE, after payment of fees, the TOB Floater holders and the TOB Residual holders would be paid pro rata in proportion to the respective face values of their certificates.

If there are insufficient proceeds from the liquidation of the TOB Trust, the party that would bear the losses would depend upon whether the Fund holds a non-recourse TOBs Residual or a recourse TOBs Residual. If the Fund holds a non-recourse TOBs Residual, the Liquidity Provider or holders of the TOBs Floaters would bear the losses on those securities and there would be no recourse to the Fund's assets. If the Fund holds a recourse TOBs Residual, the Fund (and, indirectly, holders of the Fund's Common Shares) would typically bear the losses. In particular, if the Fund holds a recourse TOBs Residual, it will typically have entered into an agreement pursuant to which the Fund would be required to pay to the Liquidity Provider the difference between the purchase price of any TOBs Floaters put to the Liquidity Provider by holders of the TOBs Floaters and the proceeds realized from the remarketing of those TOBs Floaters or the sale of the assets in the TOBs Issuer. The Fund may invest in both non-recourse and recourse TOBs Residuals to leverage its portfolio.

In December 2013, regulators finalized rules implementing Section 619 (the “Volcker Rule”) and Section 941 (the “Risk Retention Rules”) of the Dodd-Frank Wall Street Reform and Consumer Protection Act (the “Dodd-Frank Act”). Both the Volcker Rule and the Risk Retention Rules apply to tender option bond programs. The Volcker Rule precludes banking entities from (i) sponsoring or acquiring interests in the trusts used to hold a municipal bond in the creation of TOB Trusts; and (ii) continuing to service or maintain relationships with existing programs involving TOB Trusts to the same extent and in the same capacity as existing programs. The Risk Retention Rules may require the sponsor to a TOB Trust (e.g., the Fund) to retain at least five percent of the credit risk of the underlying assets supporting the TOB Trust’s municipal bonds. The Risk Retention Rules adversely affect the Fund’s ability to engage in tender option bond trust transactions or increase the costs of such transactions in certain circumstances.

In response to these rules, industry participants explored various structuring alternatives for TOB Trusts and agreed on a new tender option bond structure in which the Fund hires service providers to assist with establishing, structuring and sponsoring a TOB Trust. Service providers to a TOB Trust, such as administrators, liquidity providers, trustees and remarketing agents act at the direction of, and as agent of, the Fund as the TOB residual holders.

Under the new TOB Trust structure, the Liquidity Provider or remarketing agent will no longer purchase the tendered TOB Floaters, even in the event of failed remarketing. This may increase the likelihood that a TOB Trust will need to be collapsed and liquidated in order to purchase the tendered TOB Floaters. The TOB Trust may draw upon a loan from the Liquidity Provider to purchase the tendered TOB Floaters. Any loans

made by the Liquidity Provider will be secured by the purchased TOB Floaters held by the TOB Trust and will be subject to an interest rate agreed with the Liquidity Provider.

Bonds

The Fund may invest in a wide variety of bonds of varying maturities issued by non-U.S. (foreign) and U.S. corporations and other business entities, governments and quasi-governmental entities and municipalities and other issuers. Bonds may include, among other things, fixed or variable/floating-rate debt obligations, including bills, notes, debentures, money market instruments and similar instruments and securities. Bonds generally are used by corporations as well as governments and other issuers to borrow money from investors. The issuer pays the investor a fixed or variable rate of interest and normally must repay the amount borrowed on or before maturity. Certain bonds are “perpetual” in that they have no maturity date.

Commercial Paper

Commercial paper represents short-term unsecured promissory notes issued in bearer form by corporations such as banks or bank holding companies and finance companies. The rate of return on commercial paper may be linked or indexed to the level of exchange rates between the U.S. dollar and a foreign currency or currencies.

U.S. Government Securities

U.S. Government securities are obligations of and, in certain cases, guaranteed by, the U.S. Government, its agencies or instrumentalities. The U.S. Government does not guarantee the NAV of the Fund’s Common Shares. Some U.S. Government securities, such as Treasury bills, notes and bonds, and securities guaranteed by GNMA, are supported by the full faith and credit of the United States; others, such as those of the FHLBs, are supported by the right of the issuer to borrow from the U.S. Department of the Treasury (the “U.S. Treasury”); others, such as those of FNMA, are supported by the discretionary authority of the U.S. Government to purchase the agency’s obligations; and still others are supported only by the credit of the instrumentality. U.S. Government securities may include zero coupon securities, which do not distribute interest on a current basis and tend to be subject to greater risk than interest-paying securities of similar maturities.

Preferred Securities

Preferred securities represent an equity interest in a company that generally entitles the holder to receive, in preference to the holders of other stocks such as common stocks, dividends and a fixed share of the proceeds resulting from liquidation of the company. Unlike common stocks, preferred securities usually do not have voting rights. Preferred securities in some instances are convertible into common stock. Some preferred securities also entitle their holders to receive additional liquidation proceeds on the same basis as holders of a company’s common stock, and thus also represent an ownership interest in the company. Some preferred securities offer a fixed rate of return with no maturity date. Because they never mature, these preferred securities may act like long-term bonds, can be more volatile than other types of

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PIMCO Flexible Municipal Income Fund

preferred securities and may have heightened sensitivity to changes in interest rates. Other preferred securities have a variable dividend, generally determined on a quarterly or other periodic basis, either according to a formula based upon a specified premium or discount to the yield on particular U.S. Treasury securities or based on an auction process, involving bids submitted by holders and prospective purchasers of such securities. Although they are equity securities, preferred securities have certain characteristics of both debt securities and common stock. They are like debt securities in that their stated income is generally contractually fixed. They are like common stocks in that they do not have rights to precipitate bankruptcy proceedings or collection activities in the event of missed payments. Furthermore, preferred securities have many of the key characteristics of equity due to their subordinated position in an issuer’s capital structure and because their quality and value are heavily dependent on the profitability of the issuer rather than on any legal claims to specific assets or cash flows. Because preferred securities represent an equity ownership interest in a company, their value usually will react more strongly than bonds and other debt instruments to actual or perceived changes in a company’s financial condition or prospects, or to fluctuations in the equity markets.

In order to be payable, dividends on preferred securities must be declared by the issuer’s board of directors. In addition, distributions on preferred securities may be subject to deferral and thus may not be automatically payable. Income payments on some preferred securities are cumulative, causing dividends and distributions to accrue even if they are not declared by the board of directors of the issuer or otherwise made payable. Other preferred securities are non-cumulative, meaning that skipped dividends and distributions do not continue to accrue. There is no assurance that dividends on preferred securities in which the Fund invests will be declared or otherwise made payable.

Preferred securities have a liquidation value that generally equals their original purchase price at the date of issuance. The market values of preferred securities may be affected by favorable and unfavorable changes affecting the issuers’ industries or sectors. They also may be affected by actual and anticipated changes or ambiguities in the tax status of the security and by actual and anticipated changes or ambiguities in tax laws, such as changes in corporate and individual income tax rates or the characterization of dividends as tax-advantaged. The dividends paid on the preferred securities in which the Fund may invest might not be eligible for tax-advantaged “qualified dividend” treatment. See “Tax Matters.” Because the claim on an issuer’s earnings represented by preferred securities may become disproportionately large when interest rates fall below the rate payable on the securities or for other reasons, the issuer may redeem preferred securities, generally after an initial period of call protection in which the security is not redeemable. Thus, in declining interest rate environments in particular, the Fund’s holdings of higher dividend-paying preferred securities may be reduced and the Fund may be unable to acquire securities paying comparable rates with the redemption proceeds.

Bank Capital Securities and Bank Obligations

The Fund may invest in bank capital securities of both non-U.S. (foreign) and U.S. issuers. Bank capital securities are issued by banks to help fulfill their regulatory capital requirements. There are three common types of bank capital: Lower Tier II, Upper Tier II and Tier I. Upper Tier II securities are commonly thought of as hybrids of debt and preferred securities. Upper Tier II securities are often perpetual (with no maturity date), callable and have a cumulative interest deferral feature. This means that under certain conditions, the issuer bank can withhold payment of interest until a later date. However, such deferred interest payments generally earn interest. Tier I securities often take the form of trust preferred securities.

The Fund may also invest in other bank obligations including without limitation certificates of deposit, bankers’ acceptances and fixed time deposits. Certificates of deposit are negotiable certificates that are issued against funds deposited in a commercial bank for a definite period of time and that earn a specified return. Bankers’ acceptances are negotiable drafts or bills of exchange, normally drawn by an importer or exporter to pay for specific merchandise, which are “accepted” by a bank, meaning, in effect, that the bank unconditionally agrees to pay the face value of the instrument on maturity. Fixed time deposits are bank obligations payable at a stated maturity date and bearing interest at a fixed rate. Fixed time deposits may be withdrawn on demand by the investor, but may be subject to early withdrawal penalties which vary depending upon market conditions and the remaining maturity of the obligation. There are generally no contractual restrictions on the right to transfer a beneficial interest in a fixed time deposit to a third party, although there is generally no market for such deposits. The Fund may also hold funds on deposit with its custodian bank in an interest-bearing account for temporary purposes.

High Yield Securities

The Fund may invest without limit in debt instruments that are, at the time of purchase, rated below investment grade (below Baa3 by Moody’s or below BBB- by either S&P or Fitch), or unrated but determined by PIMCO to be of comparable quality. The Fund may invest in securities of stressed or distressed issuers, which include securities at risk of being in default as to the repayment of principal and/or interest at the time of acquisition by the Fund or that are rated in the lower rating categories by one or more nationally recognized statistical rating organizations (for example, Ca or lower by Moody’s or CC or lower by S&P or Fitch) or, if unrated, are determined by PIMCO to be of comparable quality. The Fund may invest in defaulted securities and debtor-in-possession financings. Below investment grade securities are commonly referred to as “high yield” securities or “junk bonds.” High yield securities involve a greater degree of risk (in particular, a greater risk of default) than, and special risks in addition to, the risks associated with investment grade debt obligations. While offering a greater potential opportunity for capital appreciation and higher yields, high yield securities typically entail greater potential price volatility and may be less liquid than higher-rated securities. High yield securities may be regarded as predominantly speculative with respect to the issuer’s continuing ability to make timely principal and interest payments. They

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also may be more susceptible to real or perceived adverse economic and competitive industry conditions than higher-rated securities. Debt securities in the lowest investment grade category also may be considered to possess some speculative characteristics by certain ratings agencies.

The market values of high yield securities tend to reflect individual developments of the issuer to a greater extent than do higher-quality securities, which tend to react mainly to fluctuations in the general level of interest rates. In addition, lower-quality debt securities tend to be more sensitive to general economic conditions. Certain emerging market governments that issue high yield securities in which the Fund may invest are among the largest debtors to commercial banks, foreign governments and supranational organizations, such as the World Bank, and may not be able or willing to make principal and/or interest payments as they come due.

Credit ratings and unrated securities. Rating agencies are private services that provide ratings of the credit quality of debt obligations. Appendix A to this prospectus describes the various ratings assigned to debt obligations by Moody’s, S&P and Fitch. As noted in Appendix A, Moody’s, S&P and Fitch may modify their ratings of securities to show relative standing within a rating category, with the addition of numerical modifiers (1, 2 or 3) in the case of Moody’s, and with the addition of a plus (+) or minus (-) sign in the case of S&P and Fitch. Ratings assigned by a rating agency are not absolute standards of credit quality and do not evaluate market risks. Rating agencies may fail to make timely changes in credit ratings, and an issuer’s current financial condition may be better or worse than a rating indicates. The Fund will not necessarily sell a security when its rating is reduced below its rating at the time of purchase. PIMCO does not rely solely on credit ratings, and develops its own analysis of issuer credit quality. The ratings of a debt security may change over time. Moody’s, S&P and Fitch monitor and evaluate the ratings assigned to securities on an ongoing basis. As a result, debt instruments held by the Fund could receive a higher rating (which would tend to increase their value) or a lower rating (which would tend to decrease their value) during the period in which they are held by the Fund.

The Fund may purchase unrated securities (which are not rated by a rating agency) if PIMCO determines that the security is of comparable quality to a rated security that the Fund may purchase. Unrated securities may be less liquid than comparable rated securities and involve the risk that PIMCO may not accurately evaluate the security’s comparative credit rating. Analysis of the creditworthiness of issuers of high yield securities may be more complex than for issuers of higher-quality debt obligations. The Fund’s success in achieving its investment objectives may depend more heavily on PIMCO’s credit analysis to the extent that the Fund invests in below investment grade quality and unrated securities.

Zero-Coupon Bonds, Step-Ups and Payment-In-Kind Securities

Zero-coupon bonds pay interest only at maturity rather than at intervals during the life of the security. Like zero-coupon bonds, “step up” bonds pay no interest initially but eventually begin to pay a coupon rate prior

to maturity, which rate may increase at stated intervals during the life of the security. PIKs are debt obligations that pay “interest” in the form of other debt obligations, instead of in cash. Each of these instruments is normally issued and traded at a deep discount from face value. Zero-coupon bonds, step-ups and PIKs allow an issuer to avoid or delay the need to generate cash to meet current interest payments and, as a result, may involve greater credit risk than bonds that pay interest currently or in cash. The Fund would be required to distribute the income on these instruments as it accrues, even though the Fund will not receive the income on a current basis or in cash. Thus, the Fund may have to sell investments, including when it may not be advisable to do so, to make income distributions to its shareholders.

Inflation-Indexed Bonds

Inflation-indexed bonds (other than municipal inflation-indexed bonds and certain corporate inflation-indexed bonds) are fixed income securities the principal value of which is periodically adjusted according to the rate of inflation. If the index measuring inflation falls, the principal value of inflation-indexed bonds (other than municipal inflation-indexed bonds and certain corporate inflation-indexed bonds) will be adjusted downward, and consequently the interest payable on these securities (calculated with respect to a smaller principal amount) will be reduced. Repayment of the original bond principal upon maturity (as adjusted for inflation) is guaranteed in the case of Treasury Inflation Protected Securities (“TIPS”). For bonds that do not provide a similar guarantee, the adjusted principal value of the bond repaid at maturity may be less than the original principal. TIPS may also be divided into individual zero-coupon instruments for each coupon or principal payment (known as “iSTRIPS”). An iSTRIP of the principal component of a TIPS issue will retain the embedded deflation floor that will allow the holder of the security to receive the greater of the original principal or inflation-adjusted principal value at maturity. iSTRIPS may be less liquid than conventional TIPS because they are a small component of the TIPS market. Municipal inflation-indexed securities are municipal bonds that pay coupons based on a fixed rate plus CPI. With regard to municipal inflation-indexed bonds and certain corporate inflation-indexed bonds, the inflation adjustment is typically reflected in the semi-annual coupon payment. As a result, the principal value of municipal inflation-indexed bonds and such corporate inflation-indexed bonds does not adjust according to the rate of inflation. At the same time, the value of municipal inflation-indexed securities and such corporate inflation-indexed securities generally will not increase if the rate of inflation decreases. Because municipal inflation-indexed securities and corporate inflation-indexed securities are a small component of the municipal bond and corporate bond markets, respectively, they may be less liquid than conventional municipal and corporate bonds.

The value of inflation-indexed bonds is expected to change in response to changes in real interest rates. Real interest rates are tied to the relationship between nominal interest rates and the rate of inflation. If nominal interest rates increase at a faster rate than inflation, real interest rates may rise, leading to a decrease in value of inflation-indexed bonds. Any increase in the principal amount of an

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inflation-indexed bond will be considered taxable ordinary income, even though investors do not receive their principal until maturity. See “Taxation” in the Statement of Additional Information.

Variable- and Floating-Rate Securities

Variable- and floating-rate instruments are instruments that pay interest at rates that adjust whenever a specified interest rate changes and/or that reset on predetermined dates (such as the last day of a month or calendar quarter). In addition to senior loans, variable- and floating-rate instruments may include, without limitation, instruments such as catastrophe and other event-linked bonds, bank capital securities, unsecured bank loans, corporate bonds, money market instruments and certain types of mortgage-related and other asset-backed securities. Due to their variable- or floating-rate features, these instruments will generally pay higher levels of income in a rising interest rate environment and lower levels of income as interest rates decline. For the same reason, the market value of a variable- or floating-rate instrument is generally expected to have less sensitivity to fluctuations in market interest rates than a fixed-rate instrument, although the value of a variable- or floating-rate instrument may nonetheless decline as interest rates rise and due to other factors, such as changes in credit quality.

The Fund also may engage in credit spread trades. A credit spread trade is an investment position relating to a difference in the prices or interest rates of two bonds or other securities, in which the value of the investment position is determined by changes in the difference between the prices or interest rates, as the case may be, of the respective securities.

Inverse Floaters

An inverse floater is a type of debt instrument that bears a floating or variable interest rate that moves in the opposite direction to interest rates generally or the interest rate on another security or index. Changes in interest rates generally, or the interest rate of the other security or index, inversely affect the interest rate paid on the inverse floater, with the result that the inverse floater’s price will be considerably more volatile than that of a fixed-rate bond. The Fund may invest without limit in inverse floaters, which brokers typically create by depositing an income-producing instrument, which may be a mortgage-related asset, in a trust. The trust in turn issues a variable rate security and inverse floaters. The interest rate for the variable rate security is typically determined by an index or an auction process, while the inverse floater holder receives the balance of the income from the underlying income-producing instrument less an auction fee. The market prices of inverse floaters may be highly sensitive to changes in interest rates and prepayment rates on the underlying securities, and may decrease significantly when interest rates increase or prepayment rates change. In a transaction in which the Fund purchases an inverse floater from a trust, and the underlying bond was held by the Fund prior to being deposited into the trust, the Fund typically treats the transaction as a secured borrowing for financial reporting purposes. As a result, for financial reporting purposes, the Fund will generally incur a non-cash interest expense with respect to interest paid by the trust on the variable rate securities, and will recognize additional interest income in

an amount directly corresponding to the non-cash interest expense. Therefore, the Fund’s NAV per Common Share and performance are not affected by the non-cash interest expense. This accounting treatment does not apply to inverse floaters acquired by the Fund when the Fund did not previously own the underlying bond.

Derivatives

The Fund may, but is not required to, utilize various derivative strategies (both long and short positions) for investment purposes, leveraging purposes, or in an attempt to hedge against market, credit, interest rate, currency and other risks in the portfolio. See “Use of Leverage.” Generally, derivatives are financial contracts whose value depends upon, or is derived from, the value of an underlying asset, reference rate or index, and may relate to, among others, individual debt instruments, interest rates, currencies or currency exchange rates, commodities and related indexes. Examples of derivative instruments that the Fund may use include, without limitation, futures and forward contracts (including foreign currency exchange contracts), call and put options (including options on futures contracts), credit default swaps, total return swaps, basis swaps and other swap agreements. The Fund’s use of derivative instruments involves risks different from, or possibly greater than, the risks associated with investment directly in securities and other more traditional investments. See “Principal Risks of the Fund—Derivatives Risk.” Certain types of derivative instruments that the Fund may utilize are described elsewhere in this section, including those described under “Municipal Bonds—Tender Option Bonds,” “—Certain Interest Rate Transactions,” and “—Credit Default Swaps” Please see “Investment Objectives and Policies—Derivative Instruments” in the Statement of Additional Information for additional information about these and other derivative instruments that the Fund may use and the risks associated with such instruments. There is no assurance that these derivative strategies will be available at any time or that PIMCO will determine to use them for the Fund or, if used, that the strategies will be successful. In addition, the Fund may be subject to certain restrictions on its use of derivative strategies imposed by guidelines of one or more rating agencies that may issue ratings for any Preferred Shares issued by the Fund.

Rule 144A Securities

The Fund may invest in securities that have not been registered for public sale, but that are eligible for purchase and sale pursuant to Rule 144A under the 1933 Act. Rule 144A permits certain qualified institutional buyers, such as the Fund, to trade in privately placed securities that have not been registered for sale under the 1933 Act.

Illiquid Investments

To the extent consistent with the applicable liquidity requirements for interval funds under Rule 23c-3 of the Act, the Fund may invest without limit in illiquid investments. PIMCO may be subject to significant delays in disposing of illiquid investments, and other transaction costs that are higher than those for transactions in liquid investments may entail registration expenses and other transaction costs that are higher than those for transactions in liquid investments. The term “illiquid

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investments” for this purpose means any investment that the Fund reasonably expects cannot be sold or disposed of in current market conditions in seven calendar days or less without the sale or disposition significantly changing the market value of the investment. Restricted investments, i.e., investments subject to legal or contractual restrictions on resale, may be illiquid. However, some restricted investments (such as investments issued pursuant to Rule 144A under the 1933 Act, and certain commercial paper) may be treated as liquid, although they may be relatively less liquid than registered investments traded on established secondary markets.

Other Investment Companies

In general, under the Act, an investment company such as the Fund may not (i) own more than 3% of the outstanding voting securities of any one registered investment company, (ii) invest more than 5% of its total assets in the securities of any single registered investment company or (iii) invest more than 10% of its total assets in securities of other registered investment companies.

The Fund may invest in other investment companies to gain broad market or sector exposure, including during periods when it has large amounts of uninvested cash (such as the period shortly after the Fund receives the proceeds of the offering of its Common Shares) or when PIMCO believes share prices of other investment companies offer attractive values.

As a shareholder in an investment company, the Fund will bear its ratable share of that investment company’s expenses and would remain subject to payment of the Fund’s management fees and other expenses with respect to assets so invested. Common Shareholders would therefore be subject to duplicative expenses to the extent the Fund invests in other investment companies. In addition, the securities of other investment companies may also be leveraged and will therefore be subject to the same leverage risks described in this prospectus.

Foreign (Non-U.S.) Investments

The Fund may invest in instruments of corporate and other foreign (non-U.S.) issuers, and in instruments traded principally outside of the United States. The Fund may invest in sovereign and other debt securities issued by foreign governments and their respective sub-divisions, agencies or instrumentalities, government sponsored enterprises and supranational government entities. Supranational entities include international organizations that are organized or supported by one or more government entities to promote economic reconstruction or development and by international banking institutions and related governmental agencies. As a holder of such debt securities, the Fund may be requested to participate in the rescheduling of such

debt and to extend further loans to governmental entities. In addition, there are generally no bankruptcy proceedings similar to those in the United States by which defaulted foreign debt securities may be collected. Investing in foreign securities involves special risks and considerations not typically associated with investing in U.S. securities.

PIMCO generally considers an instrument to be economically tied to a non-U.S. country if the issuer is a foreign (non-U.S.) government (or any political subdivision, agency, authority or instrumentality of such government), or if the issuer is organized under the laws of a non-U.S. country. In the case of money market instruments, other than commercial paper and certificates of deposits, such instruments will be considered economically tied to a non-U.S. country if the issuer of such money market instrument is organized under the laws of a non-U.S. country. In the case of commercial paper and certificates of deposit, such instruments will be considered economically tied to a non-U.S. country if the “country of exposure” of such instrument is a non-U.S. country, as determined by the criteria set forth below. With respect to derivative instruments, PIMCO generally considers such instruments to be economically tied to non-U.S. countries if the underlying assets are foreign currencies (or baskets or indexes of such currencies), or instruments or securities that are issued by foreign governments or issuers organized under the laws of a non-U.S. country (or if the underlying assets are money market instruments, other than commercial paper and certificates of deposit, the issuer of such money market instrument is organized under the laws of a non-U.S. country) or, in the case of underlying assets that are commercial paper or certificates of deposit, if the “country of exposure” of such money market instrument is a non-U.S. country). A security’s “country of exposure” is determined by PIMCO using certain factors provided by a third-party analytical service provider. The factors are applied in order such that the first factor to result in the assignment of a country determines the “country of exposure.” Both the factors and the order in which they are applied may change in the discretion of PIMCO. The current factors, listed in the order in which they are applied, are: (i) if an asset-backed or other collateralized security, the country in which the collateral backing the security is located; (ii) the “country of risk” of the issuer; (iii) if the security is guaranteed by the government of a country (or any political subdivision, agency, authority or instrumentality of such government), the country of the government or instrumentality providing the guarantee; (iv) the “country of risk” of the issuer’s ultimate parent; or (v) the country where the issuer is organized or incorporated under the laws thereof. “Country of risk” is a separate four-part test determined by the following factors, listed in order of importance: (i) management location; (ii) country of primary listing; (iii) sales or revenue attributable to the country; and (iv) reporting currency of the issuer. Further, where a derivative instrument is exposed to an index, PIMCO generally considers the derivative to be economically tied to each country represented by the components of the underlying index pursuant to the criteria set forth in the preceding sentence.

The Fund may invest in Brady Bonds, which are securities created through the exchange of existing commercial bank loans to sovereign entities for new obligations in connection with a debt restructuring. Investments in Brady Bonds may be viewed as speculative. Brady Bonds

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acquired by the Fund may be subject to restructuring arrangements or to requests for new credit, which may cause the Fund to realize a loss of interest or principal on any of its portfolio holdings.

The foreign securities in which the Fund may invest include without limitation Eurodollar obligations and “Yankee Dollar” obligations. Eurodollar obligations are U.S. dollar-denominated certificates of deposit and time deposits issued outside the U.S. capital markets by foreign branches of U.S. banks and by foreign banks. Yankee Dollar obligations are U.S. dollar-denominated obligations issued in the U.S. capital markets by foreign banks. Eurodollar and Yankee Dollar obligations are generally subject to the same risks that apply to domestic debt issues, notably credit risk, interest rate risk, market risk and liquidity risk. Additionally, Eurodollar (and to a limited extent, Yankee Dollar) obligations are subject to certain sovereign risks. One such risk is the possibility that a sovereign country might prevent capital, in the form of U.S. dollars, from flowing across its borders. Other risks include adverse political and economic developments; the extent and quality of government regulation of financial markets and institutions; the imposition of foreign withholding or other taxes; market disruptions, the possibility of security suspensions and the expropriation or nationalization of foreign issuers.

Short Sales

The Fund may make short sales of securities (i) to offset potential declines in long positions in similar securities, (ii) to increase the flexibility of the Fund, (iii) for investment return, (iv) as part of a risk arbitrage strategy, and (v) as part of its overall portfolio management strategies involving the use of derivative instruments. A short sale is a transaction in which the Fund sells a security it does not own in anticipation that the market price of that security will decline or will underperform relative to other securities held in the Fund’s portfolio.

When the Fund makes a short sale, it must borrow the security sold short and deliver it to the broker-dealer through which it made the short sale as collateral for its obligation to deliver the security upon conclusion of the sale. The Fund may have to pay a fee to borrow particular securities or maintain an arrangement with a broker to borrow securities, and would often be obligated to pay over any accrued interest and dividends on such borrowed securities.

A short sale is “against the box” to the extent that the Fund contemporaneously owns, or has the right to obtain at no added cost, securities identical to those sold short.

If the price of the security sold short increases between the time of the short sale and the time that the Fund replaces the borrowed security, the Fund will incur a loss; conversely, if the price declines, the Fund will realize a capital gain. Any gain will be decreased, and any loss increased, by the transaction costs described above. The successful use of short selling may be adversely affected by imperfect correlation between movements in the price of the security sold short and the securities being hedged.

The Fund may invest pursuant to a risk arbitrage strategy to take advantage of a perceived relationship between the value of two securities. Frequently, a risk arbitrage strategy involves the short sale of a security.

Under current regulatory requirements, to the extent the Fund engages in short sales, it will provide collateral to the broker-dealer and (except in the case of short sales “against the box”) will maintain additional asset coverage in the form of segregated or “earmarked” assets determined to be liquid. A short sale is “against the box” to the extent that the Fund contemporaneously owns, or has the right to obtain at no added cost, securities identical to those sold short. The Fund will engage in short selling to the extent permitted by the federal securities laws and rules and interpretations thereunder. To the extent the Fund engages in short selling in foreign (non-U.S.) jurisdictions, the Fund will do so to the extent permitted by the laws and regulations of such jurisdiction.

The Fund may also engage in so-called “naked” short sales (i.e., short sales that are not “against the box”), in which case the Fund’s losses could theoretically be unlimited, in cases where the Fund is unable for whatever reason to close out its short position. The Fund has the flexibility to engage in short selling to the extent permitted by the Act and rules and interpretations thereunder.

Certain Interest Rate Transactions

In order to reduce the interest rate risk inherent in the Fund’s underlying investments and capital structure, the Fund may (but is not required to) enter into interest rate swap transactions. Interest rate swaps involve the exchange by the Fund with a counterparty of their respective commitments to pay or receive interest, such as an exchange of fixed rate payments for floating rate payments. These transactions generally involve an agreement with the swap counterparty to pay a fixed or variable rate payment in exchange for the counterparty paying the Fund the other type of payment stream (i.e., variable or fixed). The payment obligation would be based on the notional amount of the swap. Other forms of interest rate swap agreements in which the Fund may invest include without limitation interest rate caps, under which, in return for a premium, one party agrees to make payments to the other to the extent that interest rates exceed a specified rate, or “cap;” interest rate floors, under which, in return for a premium, one party agrees to make payments to the other to the extent that interest rates fall below a specified rate, or “floor;” and interest rate “collars,” under which a party sells a cap and purchases a floor or vice versa in an attempt to protect itself against interest rate movements exceeding given minimum or maximum levels. The Fund may (but is not required to) use interest rate swap transactions with the intent to reduce or eliminate the risk that an increase in short-term interest rates could pose for the performance of the Fund’s Common Shares as a result of leverage, and also may use these instruments for other hedging or investment purposes. Any termination of an interest rate swap transaction could result in a termination payment by or to the Fund.

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Credit Default Swaps

The Fund may enter into credit default swaps for both investment and risk management purposes, as well as to add leverage to the Fund’s portfolio. A credit default swap may have as reference obligations one or more securities that are not currently held by the Fund. The protection “buyer” in a credit default swap is generally obligated to pay the protection “seller” an upfront or a periodic stream of payments over the term of the contract provided that no credit event, such as a default, on a reference obligation has occurred. If a credit event occurs, the seller generally must pay the buyer the “par value” (full notional value) of the swap in exchange for an equal face amount of deliverable obligations of the reference entity described in the swap, or the seller may be required to deliver the related net cash amount, if the swap is cash settled. Rather than exchange the bonds for par value, a single cash payment may be due from the protection seller representing the difference between the par value of the bonds and the current market value of the bonds (which may be determined through an auction). The Fund may be either the buyer or seller in the transaction. If the Fund is a buyer and no credit event occurs, the Fund may recover nothing if the swap is held through its termination date. However, if a credit event occurs, the buyer generally may elect to receive the full notional value of the swap from the seller, who, in turn, generally will recover an amount significantly lower than the equivalent face amount of the obligations of the reference entity, whose value may have significantly decreased, through (i) physical delivery of such obligations by the buyer, (ii) cash settlement or (iii) an auction process. As a seller, the Fund generally receives an upfront payment or a fixed rate of income throughout the term of the swap provided that there is no credit event. As the seller, the Fund would effectively add leverage to its portfolio because, in addition to its total net assets, the Fund would be subject to investment exposure on the notional amount of the swap.

The spread of a credit default swap is the annual amount the protection buyer must pay the protection seller over the length of the contract, expressed as a percentage of the notional amount. When spreads rise, market perceived credit risk rises and when spreads fall, market perceived credit risk falls. Wider credit spreads and decreasing market values, when compared to the notional amount of the swap, represent a deterioration of the referenced entity’s credit soundness and a greater likelihood or risk of default or other credit event occurring as defined under the terms of the agreement. For credit default swaps on asset-backed securities and credit indices, the quoted market prices and resulting values, as well as the annual payment rate, serve as an indication of the current status of the payment/performance risk.

Credit default swaps involve greater risks than if the Fund had invested in the reference obligation directly since, in addition to general market risks, credit default swaps are subject to illiquidity risk, counterparty risk and credit risk, among other risks associated with derivative instruments. A buyer generally also will lose its investment and recover nothing should no credit event occur and the swap is held to its termination date. If a credit event were to occur, the value of any deliverable obligation received by the seller, coupled with the upfront or periodic payments previously received, may be less than the full notional

value it pays to the buyer, resulting in a loss of value to the seller. The Fund’s obligations under a credit default swap will be accrued daily (offset against any amounts owing to the Fund). Under current regulatory requirements, in connection with credit default swaps in which the Fund is the buyer, the Fund may segregate or “earmark” cash or liquid assets, or enter into certain offsetting positions, with a value at least equal to the Fund’s exposure (any accrued but unpaid net amounts owed by the Fund to any counterparty), on a marked-to-market basis. Under current regulatory requirements, in connection with credit default swaps in which the Fund is the seller, if the Fund covers its position through asset segregation, the Fund will segregate or “earmark” cash or assets determined to be liquid with a value at least equal to the full notional amount of the Fund’s obligation under the swap. Such segregation or “earmarking” will not limit the Fund’s exposure to loss. See “Principal Risks of the Fund—Segregation and Coverage Risk.”

When-Issued, Delayed Delivery and Forward Commitment Transactions

The Fund may purchase or sell securities that it is eligible to purchase or sell on a when-issued basis, may purchase and sell such securities for delayed delivery and may make contracts to purchase or sell such securities for a fixed price at a future date beyond normal settlement time (forward commitments). When-issued transactions, delayed delivery purchases and forward commitments involve a risk of loss if the value of the securities declines prior to the settlement date. This risk is in addition to the risk that the Fund’s other assets will decline in value. Therefore, these transactions may result in a form of leverage and increase the Fund’s overall investment exposure. Typically, no income accrues on securities the Fund has committed to purchase prior to the time delivery of the securities is made, although the Fund may earn income on securities it has segregated or “earmarked” to cover these positions. When the Fund has sold a security on a when-issued, delayed delivery, or forward commitment basis, the Fund does not participate in future gains or losses with respect to the security. If the other party to a transaction fails to pay for the securities, the Fund could suffer a loss. Additionally, when selling a security on a when-issued, delayed delivery, or forward commitment basis without owning the security, the Fund will incur a loss if the security’s price appreciates in value such that the security’s price is above the agreed-upon price on the settlement date.

Repurchase Agreements

The Fund may enter into repurchase agreements, in which the Fund purchases a security from a bank or broker-dealer, which agrees to repurchase the security at the Fund’s cost plus interest within a specified time. If the party agreeing to repurchase should default, the Fund will seek to sell the securities which it holds. This could involve procedural costs or delays in addition to a loss on the securities if their value should fall below their repurchase price.

Lending of Portfolio Securities

For the purpose of achieving income, the Fund may lend its portfolio securities to brokers, dealers or other financial institutions provided a number of conditions are satisfied, including that the loan is fully

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collateralized. See “Investment Objectives and Policies—Securities Loans” in the Statement of Additional Information for details. When the Fund lends portfolio securities, its investment performance will continue to reflect changes in the value of the securities loaned. The Fund will also receive a fee or interest on the collateral. Securities lending involves the risk of loss of rights in the collateral or delay in recovery of the collateral if the borrower fails to return the security loaned or becomes insolvent, or the risk of loss due to the investment performance of the collateral. The Fund may pay lending fees to the party arranging the loan, which may be an affiliate of the Fund. See “Principal Risks of the Fund—Securities Lending Risk.”

Portfolio Turnover

The length of time the Fund has held a particular security is not generally a consideration in investment decisions. A change in the securities held by the Fund is known as “portfolio turnover.” The Fund may engage in frequent and active trading of portfolio securities to achieve its investment objectives, particularly during periods of volatile market movements. High portfolio turnover (e.g., over 100%) generally involves correspondingly greater expenses to the Fund, including brokerage commissions or dealer mark-ups and other transaction costs on the sale of securities and reinvestments in other securities. Sales of portfolio securities may also result in realization of taxable capital gains, including short-term capital gains (which are generally treated as ordinary income upon distribution in the form of dividends). The trading costs and tax effects associated with portfolio turnover may adversely affect the Fund’s performance.

Please see “Investment Objectives and Policies” in the Statement of Additional Information for additional information regarding the investments of the Fund and their related risks.

Use of Leverage

The Fund currently utilizes leverage through its outstanding Variable Rate MuniFund Term Preferred Shares (“VMTP Shares”) and Remarketable Variable Rate MuniFund Term Preferred Shares (“RVMTP Shares” and, together with VMTP Shares and any other preferred shares the Fund may have outstanding, “Preferred Shares”) and the use of tender option bonds. The Fund may also choose to add leverage through the issuance of additional Preferred Shares, or the use of reverse repurchase agreements, credit default swaps, dollar rolls or borrowings, such as through bank loans or commercial paper and/or other credit facilities. The Fund may also enter into transactions other than those noted above that may give rise to a form of leverage including, among others, futures and forward contracts (including foreign currency exchange contracts), total return swaps and other derivative transactions, loans of portfolio securities, short sales and when-issued, delayed delivery and forward commitment transactions.

The Fund may also determine to increase its leverage through the issuance of additional Preferred Shares, or decrease the leverage it currently maintains through its outstanding Preferred Shares through Preferred Share redemptions or tender offers and may or may not determine to replace such leverage. The Fund may issue additional Preferred Shares without the approval of holders of Common Shares (“Common Shareholders”). If the Fund issues additional Preferred Shares in the future, all costs and expenses relating to the issuance and ongoing maintenance of the Preferred Shares will be borne by the Common Shareholders, and these costs and expenses may be significant. The Fund’s net assets attributable to its Preferred Shares and the net proceeds the Fund obtains from the issuance of additional preferred shares or the use of tender option bonds or other forms of leverage will be invested in accordance with the Fund’s investment objectives and policies as described in this prospectus. So long as the rate of return, net of applicable Fund expenses, on the debt obligations and other investments purchased by the Fund exceeds the dividend rates payable on the Preferred Shares together with the costs to the Fund of other leverage it utilizes, the investment of the Fund’s assets attributable to leverage will generate more income than will be needed to pay the costs of the leverage. If so, and all other things being equal, the excess may be used to pay higher dividends to Common Shareholders than if the Fund were not so leveraged.

The Act also generally prohibits the Fund from engaging in most forms of leverage representing indebtedness other than Preferred Shares (including the use of tender option bonds, to the extent that these instruments are not covered as described below) unless immediately after the issuance of the leverage the Fund has satisfied the asset coverage test with respect to senior securities representing indebtedness prescribed by the Act; that is, the value of the Fund’s total assets less all liabilities and indebtedness not represented by senior securities (for these purposes, “total net assets”) is at least 300% of the senior securities representing indebtedness (effectively limiting the use of leverage through senior securities representing indebtedness to 33 1/3% of the Fund’s total net assets, including assets attributable to such leverage). In addition, the Fund is not permitted to declare any cash dividend or other distribution on its Common Shares unless, at the time of such declaration, this asset coverage test is satisfied. The Fund may (but is not required to) cover its commitments under tender option bonds or other derivatives instruments by the segregation of liquid assets, or by entering into offsetting transactions or owning positions

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covering its obligations. To the extent that certain of these instruments are so covered, they will not be considered “senior securities” under the Act and therefore will not be subject to the Act 300% asset coverage requirement otherwise applicable to forms of senior securities representing indebtedness used by the Fund. However, such instruments, even if covered, represent a form of economic leverage and create special risks. The use of these forms of leverage increases the volatility of the Fund’s investment portfolio and could result in larger losses to Common Shareholders than if these strategies were not used. See “Principal Risks of the Fund—Leverage Risk.”

On October 28, 2020, the SEC adopted Rule 18f-4 under the Act providing for the regulation of a registered investment company’s use of derivatives and certain related instruments. Among other things, Rule 18f-4 limits a fund’s derivatives exposure through a value-at-risk test and requires the adoption and implementation of a derivatives risk management program for certain derivatives users. Subject to certain conditions, limited derivatives users (as defined in Rule 18f-4), however, would not be subject to the full requirements of Rule 18f-4. In connection with the adoption of Rule 18f-4, the SEC also eliminated the asset segregation framework arising from prior SEC guidance for covering derivatives and certain financial instruments. Compliance with Rule 18f-4 will not be required until August 19, 2022. As the Fund comes into compliance, the Fund’s approach to asset segregation and coverage requirements described in this Prospectus will be impacted. In addition, Rule 18f-4 could restrict the Fund’s ability to engage in certain derivatives transactions and/or increase the costs of such derivatives transactions, which could adversely affect the value or performance of the Fund and the Common Shares and/or the Fund’s distribution rate.

The Fund’s ability to utilize leverage may also be limited by asset coverage requirements and other guidelines imposed by the terms of the Preferred Shares or imposed by rating agencies that provide ratings for the Preferred Shares which are more restrictive than the limitations imposed by the Act noted above.

Effects of Leverage

The following table is furnished in response to requirements of the SEC. It is designed to illustrate the effects of leverage through the use of senior securities, as that term is defined under Section 18 of the Act, on Common Share total return, assuming investment portfolio total returns (consisting of income and changes in the value of investments held in the Fund’s portfolio) of -10%, -5%, 0%, 5% and 10%. The table below assumes the Fund’s continued use of Preferred Shares representing approximately 23.99% of the Fund’s total managed assets and the Fund’s utilization of tender option bonds in an amount equal to 3.69% of the Fund’s total managed assets. The table below also assumes that the Fund will pay dividends on Preferred Shares at an estimated annual effective

Preferred Share dividend rate of 1.15% (based on the Preferred Share dividend rate under current market conditions, and including the amortization of Preferred Shares offerings costs of $1,645,314 over the three-year term of the Preferred Shares) and interest on tender option bonds at an estimated annual effective interest expense rate of 0.90%, which is based on current market conditions. Based on such estimates, the annual return that the Fund’s portfolio must experience (net of expenses) in order to cover the costs of the Fund’s leverage would be 0.28%. The information below does not reflect the Fund’s potential use of certain other forms of economic leverage achieved through the use of other instruments or transactions not considered to be senior securities under the Act, such as certain derivative instruments.

These assumed investment portfolio returns are hypothetical figures and are not necessarily indicative of the investment portfolio returns experienced or expected to be experienced by the Fund. Your actual returns may be greater or less than those appearing below. In addition, actual borrowing expenses associated with the use of tender option bonds or the issuance of Preferred Shares by the Fund may vary frequently and may be significantly higher or lower than the rate used for the example below.

Assumed Portfolio Total Return (net of expenses)	(10.00)%	(5.00)%	0.00%	5.00%	10.00%
Common Shares Total Return	(13.65)%	(7.01)%	(0.38)%	6.26%	12.89%

Common Shares Total Return is composed of two elements — the distributions paid by the Fund to holders of Common Shares (the amount of which is largely determined by the net investment income of the Fund after paying dividend payments on any Preferred Shares issued by the Fund and expenses on any forms of leverage outstanding) and gains or losses on the value of the securities and other instruments the Fund owns. As required by SEC rules, the table assumes that the Fund is more likely to suffer capital losses than to enjoy capital appreciation. For example, to assume a total return of 0%, the Fund must assume that

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the income it receives on its investments is entirely offset by losses in the value of those investments. This table reflects hypothetical performance of the Fund’s portfolio and not the actual performance of the Fund’s Common Shares, the value of which is determined by market forces and other factors.

Should the Fund elect to add additional leverage, any benefits of such leverage cannot be fully achieved until the proceeds resulting from the use of such leverage have been received by the Fund and invested in accordance with the Fund’s investment objectives and policies. As noted above, the Fund’s willingness to use leverage, and the extent to which leverage is used at any time, will depend on many factors, including, among other things, PIMCO’s assessment of the yield curve environment, interest rate trends, market conditions and other factors.

Principal Risks of the Fund

The NAV of the Common Shares will fluctuate with and be affected by, among other things, various principal risks of the Fund and its investments which are summarized below.

Interest Rate Risk

Interest rate risk is the risk that fixed income securities and other instruments in the Fund’s portfolio will decline in value because of a change in interest rates. As nominal interest rates rise, the value of certain fixed income securities held by the Fund is likely to decrease. A nominal interest rate can be described as the sum of a real interest rate and an expected inflation rate. Interest rate changes can be sudden and unpredictable, and the Fund may lose money as a result of movements in interest rates. The Fund may not be able to effectively hedge against changes in interest rates or may choose not to do so for cost or other reasons.

A wide variety of factors can cause interest rates to rise (e.g., central bank monetary policies, inflation rates, general economic conditions). This risk may be particularly acute in the current market environment because market interest rates are currently near historically low levels. Thus, the Fund currently faces a heightened level of interest rate risk.

Fixed income securities with longer durations tend to be more sensitive to changes in interest rates, usually making them more volatile. Duration is a measure used to determine the sensitivity of a security’s price to changes in interest rates that incorporates a security’s yield, coupon, final maturity and call features, among other characteristics. Duration is useful primarily as a measure of the sensitivity of a fixed income security’s market price to interest rate (i.e., yield) movements. All other things remaining equal, for each one percentage point increase in interest rates, the value of a portfolio of fixed income investments would generally be expected to decline by one percent for every year of the portfolio’s average duration above zero. For example, the value of a portfolio of fixed income securities with an average duration of eight years would generally be expected to decline by approximately 8% if interest rates rose by one percentage point.

Variable and floating rate securities may decline in value if their interest rates do not rise as much, or as quickly, as interest rates in general. Conversely, floating rate securities will not generally increase in value if

interest rates decline. Inverse floating rate securities may decrease in value if interest rates increase. Inverse floating rate securities may also exhibit greater price volatility than a fixed rate obligation with similar credit quality. When the Fund holds variable or floating rate securities, a decrease (or, in the case of inverse floating rate securities, an increase) in market interest rates will adversely affect the income received from such securities and the NAV of the Fund’s shares.

During periods of very low or negative interest rates, the Fund may be unable to maintain positive returns. Interest rates in the United States and many parts of the world are at or near historically low levels. Very low or negative interest rates may magnify interest rate risk. Changing interest rates, including rates that fall below zero, may have unpredictable effects on markets, may result in heightened market volatility and may detract from Fund performance to the extent the Fund is exposed to such interest rates.

Measures such as average duration may not accurately reflect the true interest rate sensitivity of the Fund. This is especially the case if the Fund consists of securities with widely varying durations. Therefore, if the Fund has an average duration that suggests a certain level of interest rate risk, the Fund may in fact be subject to greater interest rate risk than the average would suggest. This risk is greater to the extent the Fund uses leverage or derivatives in connection with the management of the Fund.

Convexity is an additional measure used to understand a security’s or Fund’s interest rate sensitivity. Convexity measures the rate of change of duration in response to changes in interest rates. With respect to a security’s price, a larger convexity (positive or negative) may imply more dramatic price changes in response to changing interest rates. Convexity may be positive or negative. Negative convexity implies that interest rate increases result in increased duration, meaning increased sensitivity in prices in response to rising interest rates. Thus, securities with negative convexity, which may include bonds with traditional call features and certain mortgage-backed securities, may experience greater losses in periods of rising interest rates. Accordingly, if the Fund holds such securities, the Fund may be subject to a greater risk of losses in periods of rising interest rates.

Rising interest rates may result in a decline in value of the Fund’s municipal bond investments and in periods of volatility. Further, while U.S. bond markets have steadily grown over the past three decades, dealer “market making” ability has remained relatively stagnant. As a result, dealer inventories of certain types of bonds and similar instruments, which provide a core indication of the ability of financial intermediaries to “make markets,” are at or near historic lows in relation to market size. Because market makers provide stability to a market through their intermediary services, a significant reduction in dealer inventories could potentially lead to decreased liquidity and increased volatility in the fixed income markets. Such issues may be exacerbated during periods of economic uncertainty. All of these factors, collectively and/or individually, could cause the Fund to lose value.

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Municipal Bond Risk

The Fund may invest in trust certificates issued in tender option bond programs. In these programs, a trust typically issues two classes of certificates and uses the proceeds to purchase municipal securities having relatively long maturities and bearing interest at a fixed interest rate substantially higher than prevailing short-term tax-exempt rates. There is a risk that the Fund will not be considered the owner of a tender option bond for federal income tax purposes, and thus will not be entitled to treat such interest as exempt from federal income tax. Certain tender option bonds may be less liquid or may become less liquid as a result of, among other things, a credit rating downgrade, a payment default or a disqualification from tax-exempt status. The Fund’s investment in the securities issued by a tender option bond trust may involve greater risk and volatility than an investment in a fixed rate bond, and the value of such securities may decrease significantly when market interest rates increase. Tender option bond trusts could be terminated due to market, credit or other events beyond the Fund’s control, which could require the Fund to dispose of portfolio investments at inopportune times and prices. The Fund may use a tender option bond program as a way of achieving leverage in its portfolio, in which case the Fund will be subject to leverage risk.

Municipal securities are also subject to interest rate, credit, and liquidity risk.

Credit Risk. The risk that a borrower may be unable to make interest or principal payments when they are due. Funds that invest in municipal securities rely on the ability of the issuer to service its debt. This subjects the Fund to credit risk in that the municipal issuer may be fiscally unstable or exposed to large liabilities that could impair its ability to honor its obligations. Municipal issuers with significant debt service requirements, in the near-to mid-term; unrated issuers and those with less capital and liquidity to absorb additional expenses may be most at risk. To the extent the Fund invests in lower quality or high yield municipal securities, it may be more sensitive to the adverse credit events in the municipal market. The treatment of municipalities in bankruptcy is more uncertain, and potentially more adverse to debt holders, than for corporate issues.

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imbalances. Depending on the particular issuer and current economic conditions, municipal securities could be deemed more volatile investments.

In addition to general municipal market risks, different municipal sectors may face different risks. For instance, general obligation bonds are secured by the full faith, credit, and taxing power of the municipality issuing the obligation. As such, timely payment depends on the municipality's ability to raise tax revenue and maintain a fiscally sound budget. The timely payments may also be influenced by any unfunded pension liabilities or other post-employee benefit plan (OPEB) liabilities.

Revenue bonds are secured by special tax revenues or other revenue sources. If the specified revenues do not materialize, then the bonds may not be repaid.

Similarly, changes to state or federal regulation tied to a specific sector, such as the hospital sector, could have an impact on the revenue stream for a given subset of the market.

Puerto Rico-Specific Risk

Municipal obligations issued by the Commonwealth of Puerto Rico or its political subdivisions, agencies, instrumentalities, or public corporations may be affected by economic, market, political, environmental and social conditions in Puerto Rico. Puerto Rico currently is experiencing significant fiscal and economic challenges, including substantial debt service obligations, high levels of unemployment, underfunded public retirement systems, and persistent government budget deficits. These challenges may negatively affect the value of the Fund’s investments in Puerto Rico municipal securities. Major ratings agencies have downgraded the general obligation debt of Puerto Rico to below

investment grade and continue to maintain a negative outlook for this debt, which increases the likelihood that the rating will be lowered further or discontinued. Puerto Rico has previously defaulted on its debt by failing to make full payment due on its outstanding bonds, and there can be no assurance that Puerto Rico will be able to satisfy its future debt obligations. Further downgrades or defaults may place additional strain on the Puerto Rican economy and may negatively affect the value, liquidity, and volatility of the Fund’s investments in Puerto Rico municipal securities. Legislation, including legislation that would allow Puerto Rico to restructure its municipal debt obligations, thus increasing the risk that Puerto Rico may never pay off municipal indebtedness, or may pay only a small fraction of the amount owed, could also impact the value of the Fund’s investments in Puerto Rico municipal securities.

These challenges and uncertainties have been exacerbated by recent natural disasters that have struck Puerto Rico. In September 2017, two successive hurricanes caused significant damage to Puerto Rico, and resulted in severe flooding and infrastructure damage, including damage to the Commonwealth’s water, power, and telecommunications infrastructure, and resulted in more than 1 million people losing power. Estimates suggest that the hurricanes caused more than $80 billion in damage, which led to additional strain on Puerto Rico’s economic situation. In late December 2019 and January 2020, a series of earthquakes caused an estimated $200 million in damage to Puerto Rico. The aftershocks from these earthquakes may continue for years, and it is not currently possible to predict the extent of the damage that could arise from any aftershocks. The length of time needed to rebuild Puerto Rico’s infrastructure is unclear, but could amount to years, during which the Commonwealth is likely to be in an uncertain economic state. The full extent of the negative impact of these (or future) natural disasters on Puerto Rico’s economy and foreign investment in Puerto Rico is difficult to estimate.

Municipal Project-Specific Risk

California State-Specific Risk

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difficulties in the past and reoccurrence of these difficulties may impair the ability of certain California issuers to pay principal or interest on their obligations. Provisions of the California Constitution and State statutes that limit the taxing and spending authority of California governmental entities may impair the ability of California issuers to pay principal and/or interest on their obligations. While California’s economy is broad, it does have major concentrations in advanced technology, aerospace and defense-related manufacturing, trade, entertainment, real estate and financial services, and may be sensitive to economic problems affecting those industries. Future California political and economic developments, constitutional amendments, legislative measures, executive orders, administrative regulations, litigation and voter initiatives could have an adverse effect on the debt obligations of California issuers.

New York State-Specific Risk

Insurance Risk

The Fund may purchase municipal securities that are secured by insurance, bank credit agreements or escrow accounts. The credit quality of the companies that provide such credit enhancements will affect the value of those securities. Certain significant providers of insurance for municipal securities have incurred significant losses as a result of exposure to sub-prime mortgages and other lower credit quality investments that have experienced recent defaults or otherwise suffered extreme credit deterioration. As a result, such losses have reduced the insurers’ capital and called into question their continued ability to perform their obligations under such insurance if they are called upon to do so in the future. If the insurer of a municipal security suffers a downgrade in its credit rating or the market discounts the value of the insurance provided by the insurer, the rating of the underlying municipal security will be more relevant and the value of the municipal security would more closely, if not entirely, reflect such rating. In such a case, the value of insurance associated with a municipal security would decline and may not add any value. The insurance feature of a municipal security does not guarantee the full payment of principal and interest

through the life of an insured obligation, the market value of the insured obligation or the net asset value of the common shares represented by such insured obligation.

Inflation/Deflation Risk

Call Risk

Credit Risk

The Fund could lose money if the issuer or guarantor of a fixed income security (including a security purchased with securities lending collateral), or the counterparty to a derivatives contract, repurchase agreement or a loan of portfolio securities, is unable or unwilling, or is perceived (whether by market participants, rating agencies, pricing services or otherwise) as unable or unwilling, to make timely principal and/or interest payments, or to otherwise honor its obligations. The downgrade of the credit of a security held by the Fund may decrease its value. Securities are subject to varying degrees of credit risk, which are often reflected in credit ratings. Measures such as average credit quality may not accurately reflect the true credit risk of the Fund. This is especially the case if the Fund consists of securities with widely varying credit ratings. Therefore, if the Fund has an average credit rating that suggests a certain credit quality, the Fund may in fact be subject to greater credit risk than the average would suggest. This risk is greater to the extent the Fund uses leverage or derivatives in connection with the management of the Fund. Municipal bonds are subject to the risk that litigation, legislation or other political events, local business or economic conditions, or the bankruptcy of the issuer could have a significant effect on an issuer’s ability to make payments of principal and/or interest.

Issuer Risk

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affect securities markets as a whole. These risks can apply to the Common Shares issued by the Fund and to the issuers of securities and other instruments in which the Fund invests.

Liquidity Risk

To the extent consistent with the applicable liquidity requirements for interval funds under Rule 23c-3 of the Act, the Fund may invest without limit in illiquid investments. Liquidity risk exists when particular investments are difficult to purchase or sell. Illiquid investments are investments that the Fund reasonably expects cannot be sold or disposed of in current market conditions in seven calendar days or less without the sale or disposition significantly changing the market value of the investment. Illiquid investments may become harder to value, especially in changing markets. The Fund’s investments in illiquid investments may reduce the returns of the Fund because it may be unable to sell the illiquid investments at an advantageous time or price or possibly require the Fund to dispose of other investments at unfavorable times or prices in order to satisfy its obligations, which could prevent the Fund from taking advantage of other investment opportunities. Additionally, the market for certain investments may become illiquid under adverse market or economic conditions independent of any specific adverse changes in the conditions of a particular issuer. Bond markets have consistently grown over the past three decades while the capacity for traditional dealer counterparties to engage in fixed income trading has not kept pace and in some cases has decreased. As a result, dealer inventories of corporate bonds, which provide a core indication of the ability of financial intermediaries to “make markets,” are at or near historic lows in relation to market size. Because market makers seek to provide stability to a market through their intermediary services, the significant reduction in dealer inventories could potentially lead to decreased liquidity and increased volatility in the fixed income markets. Such issues may be exacerbated during periods of economic uncertainty.

In such cases, the Fund, due to limitations on investments in illiquid investments and the difficulty in purchasing and selling such securities or instruments, may be unable to achieve its desired level of exposure to a certain sector. To the extent that the Fund invests in securities of companies with smaller market capitalizations, foreign (non-U.S.) securities, Rule 144A securities, illiquid sectors of fixed income securities, derivatives or securities with substantial market and/or credit risk, the Fund will tend to have greater exposure to liquidity risk.

Further, fixed income securities with longer durations until maturity face heightened levels of liquidity risk as compared to fixed income securities with shorter durations until maturity. The risks associated with illiquid instruments may be particularly acute in situations in which the Fund’s operations require cash (such as in connection with repurchase offers) and could result in the Fund borrowing to meet its short-term needs or incurring losses on the sale of illiquid instruments. See “Principal Risks of the Fund —Repurchase Offers Risk.” It may also be the case that other market participants may be attempting to liquidate fixed income holdings at the same time as the Fund, causing increased supply in the market and contributing to liquidity risk and downward pricing pressure. See “Principal Risks of the Fund—Valuation Risk.”

Repurchase Offers Risk

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and the date on which the NAV for tendered Common Shares is determined. In addition, the repurchase of Common Shares by the Fund may be a taxable event to shareholders.

High Yield Securities Risk

To the extent that the Fund invests in high yield securities and unrated securities of similar credit quality (commonly known as “high yield securities” or “junk bonds”), the Fund may be subject to greater levels of credit risk, call risk and liquidity risk than funds that do not invest in such securities, which could have a negative effect on the NAV of the Fund’s Common Shares or Common Share dividends. These securities are considered predominantly speculative with respect to an issuer’s continuing ability to make principal and interest payments, and may be more volatile than other types of securities. An economic downturn or individual corporate developments could adversely affect the market for these securities and reduce the Fund’s ability to sell these securities at an advantageous time or price. An economic downturn would generally lead to a higher non-payment rate and, a high yield security may lose significant market value before a default occurs. The Fund may purchase distressed securities that are in default or the issuers of which are in bankruptcy, which involve heightened risks.

High yield securities structured as zero-coupon bonds or pay-in-kind securities tend to be especially volatile as they are particularly sensitive to downward pricing pressures from rising interest rates or widening spreads and may require the Fund to make taxable distributions of imputed income without receiving the actual cash currency. Issuers of high yield securities may have the right to “call” or redeem the issue prior to maturity, which may result in the Fund having to reinvest the proceeds in other high yield securities or similar instruments that may pay lower interest rates. The Fund may also be subject to greater levels of liquidity risk than funds that do not invest in high yield securities. Consequently, transactions in high yield securities may involve greater costs than transactions in more actively traded securities. A lack of publicly-available information, irregular trading activity and wide bid/ask spreads among other factors, may, in certain circumstances, make high yield debt more difficult to sell at an advantageous time or price than other types of securities or instruments.

These factors may result in the Fund being unable to realize full value for these securities and/or may result in the Fund not receiving the proceeds from a sale of a high yield security for an extended period after such sale, each of which could result in losses to the Fund. Because of the risks involved in investing in high yield securities, an investment in the Fund should be considered speculative.

the Fund is not required to dispose of a security in the event that a rating agency or PIMCO downgrades its assessment of the credit characteristics of a particular issue. In determining whether to retain or sell such a security, PIMCO may consider factors including, but not limited to, PIMCO’s assessment of the credit quality of the issuer of such security, the price at which such security could be sold and the rating, if any, assigned to such security by other rating agencies. Analysis of creditworthiness may be more complex for issuers of high yield securities than for issuers of higher quality debt securities.

Market Risk

The market price of securities owned by the Fund may go up or down, sometimes rapidly or unpredictably. Securities may decline in value due to factors affecting securities markets generally or particular industries represented in the securities markets. The value of a security may decline due to general market conditions that are not specifically related to a particular company, such as real or perceived adverse economic conditions, changes in the general outlook for corporate earnings, changes in interest or currency rates, adverse changes to credit markets or adverse investor sentiment generally. The value of a security may also decline due to factors that affect a particular industry or industries, such as labor shortages or increased production costs and competitive conditions within an industry. During a general downturn in the securities markets, multiple asset classes may decline in value simultaneously. Equity securities generally have greater price volatility than fixed income securities. Credit ratings downgrades may also negatively affect securities held by the Fund. Even when markets perform well, there is no assurance that the investments held by the Fund will increase in value along with the broader market.

In addition, market risk includes the risk that geopolitical and other events will disrupt the economy on a national or global level. For instance, war, terrorism, market manipulation, government defaults, government shutdowns, political changes or diplomatic developments, public health emergencies (such as the spread of infectious diseases, pandemics and epidemics) and natural/environmental disasters can all negatively impact the securities markets, which could cause the Fund to lose value. These events could reduce consumer demand or economic output, result in market closures, travel restrictions or quarantines, and significantly adversely impact the economy. The current contentious domestic political environment, as well as political and diplomatic events within the United States and abroad, such as presidential elections in the U.S. or abroad or the U.S. government's inability at times to agree on a long-term budget and deficit reduction plan, has in the past resulted, and may in the future result, in a government shutdown or otherwise adversely affect the U.S. regulatory landscape, the general market environment and/or investor sentiment, which could have an adverse impact on the Fund's investments and operations. Additional and/or prolonged U.S. federal government shutdowns may affect investor and consumer confidence and may adversely impact financial markets and the broader economy, perhaps suddenly and to a significant degree. Governmental and quasi-governmental authorities and regulators throughout the world have previously responded to serious economic disruptions with a variety of significant fiscal and

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monetary policy changes, including but not limited to, direct capital infusions into companies, new monetary programs and dramatically lower interest rates. An unexpected or sudden reversal of these policies, or the ineffectiveness of these policies, could increase volatility in securities markets, which could adversely affect the Fund's investments. Any market disruptions could also prevent the Fund from executing advantageous investment decisions in a timely manner. Funds that have focused their investments in a region enduring geopolitical market disruption will face higher risks of loss, although the increasing interconnectivity between global economies and financial markets can lead to events or conditions in one country, region or financial market adversely impacting a different country, region or financial market. Thus, investors should closely monitor current market conditions to determine whether the Fund meets their individual financial needs and tolerance for risk.

Current market conditions may pose heightened risks with respect to the Fund’s investment in fixed income securities. Interest rates in the U.S. are near historically low levels. Any interest rate increases in the future could cause the value of any Fund that invests in fixed income securities to decrease. As such, fixed income securities markets may experience heightened levels of interest rate, volatility and liquidity risk.

Exchanges and securities markets may close early, close late or issue trading halts on specific securities, which may result in, among other things, the Fund being unable to buy or sell certain securities or financial instruments at an advantageous time or accurately price its portfolio investments.

Management Risk

strategies targeting perceived pricing inefficiencies, arbitrage strategies or similar strategies, it is subject to the risk that the pricing or valuation of the securities and instruments involved in such strategies may change unexpectedly, which may result in reduced returns or losses to the Fund. The Fund is also subject to the risk that deficiencies in the internal systems or controls of PIMCO or another service provider will cause losses for the Fund or hinder Fund operations. For example, trading delays or errors (both human and systematic) could prevent the Fund from purchasing a security expected to appreciate in value. Additionally, actual or potential conflicts of interest, legislative, regulatory, or tax restrictions, policies or developments may affect the investment techniques available to PIMCO and each individual portfolio manager in connection with managing the Fund and may also adversely affect the ability of the Fund to achieve its investment objectives. There also can be no assurance that all of the personnel of PIMCO will continue to be associated with PIMCO for any length of time. The loss of the services of one or more key employees of PIMCO could have an adverse impact on the Fund’s ability to realize its investment objectives.

Reinvestment Risk

Leverage Risk

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accordance with the Fund’s investment objectives and policies as described in this prospectus. Dividends payable with respect to any Preferred Shares outstanding and interest expense payable by the Fund with respect to any tender option bonds, derivatives and other forms of leverage will generally be based on shorter-term interest rates that would be periodically reset. So long as the Fund’s portfolio investments provide a higher rate of return (net of applicable Fund expenses) than the dividend rate on any Preferred Shares outstanding, including the Preferred Shareholder Gross-Up, and the interest expenses and other costs to the Fund of such other leverage, the investment of the proceeds thereof will generate more income than will be needed to pay the costs of the leverage. If so, and all other things being equal, the excess may be used to pay higher dividends to Common Shareholders than if the Fund were not so leveraged. If, however, shorter-term interest rates rise relative to the rate of return on the Fund’s portfolio, the interest and other costs to the Fund of leverage (including interest expenses on tender option bonds and the dividend rate on any outstanding Preferred Shares, including the Preferred Shareholder Gross-Up) could exceed the rate of return on the debt obligations and other investments held by the Fund, thereby reducing return to Common Shareholders. In addition, fees and expenses of any form of leverage used by the Fund will be borne entirely by the Common Shareholders (and not by Preferred Shareholders, if any) and will reduce the investment return of the Common Shares. Therefore, there can be no assurance that the Fund’s use of leverage will result in a higher yield on the Common Shares, and it may result in losses. In addition, any Preferred Shares issued by the Fund are expected to pay cumulative dividends, which may tend to increase leverage risk.

Leverage creates several major types of risks for Common Shareholders, including:

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the likelihood of greater volatility of NAV of Common Shares, and of the investment return to Common Shareholders, than a comparable portfolio without leverage;

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distributions and total returns to Common Shareholders. Under current regulatory requirements, the Fund manages some of its derivative positions by segregating an amount of cash or liquid securities equal to the notional value or the market value, as applicable, of those positions. See “Principal Risks of the Fund—Segregation and Coverage Risk.” The Fund may also offset derivatives positions against one another or against other assets to manage effective market exposure resulting from derivatives in its portfolio. To the extent that any offsetting positions do not behave in relation to one another as expected, the Fund may perform as if it is leveraged through use of these derivative strategies. See “Use of Leverage.”

The Fund is required to satisfy certain regulatory and rating agency asset coverage requirements in connection with its use of Preferred Shares. Accordingly, any decline in the net asset value of the Fund’s investments could result in the risk that the Fund will fail to meet its asset coverage requirements for any such Preferred Shares or the risk of the Preferred Shares being downgraded by a rating agency. In an extreme case, the Fund’s current investment income might not be sufficient to meet the dividend requirements on any Preferred Shares outstanding. In order to address these types of events, the Fund might need to liquidate investments in order to fund a redemption of some or all of Preferred Shares. Liquidation at times of adverse economic conditions may result in a loss to the Fund. At other times, these liquidations may result in gain at the Fund level and thus in additional taxable distributions to Common Shareholders. See “Tax Matters” for more information. Any Preferred Shares, tender option bonds, loans of portfolio securities, short sales and when-issued, delayed delivery and forward commitment transactions, credit default swaps, reverse repurchases, or other derivatives by the Fund or counterparties to the Fund’s other leveraging transactions, if any, would have, seniority over the Fund’s Common Shares.

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connection with the adoption of Rule 18f-4, the SEC also eliminated the asset segregation framework arising from prior SEC guidance for covering derivatives and certain financial instruments. Compliance with Rule 18f-4 will not be required until August 19, 2022. As the Fund comes into compliance, the Fund’s approach to asset segregation and coverage requirements described in this Prospectus will be impacted. In addition, Rule 18f-4 could restrict the Fund’s ability to engage in certain derivatives transactions and/or increase the costs of such derivatives transactions, which could adversely affect the value or performance of the Fund and the Common Shares and/or the Fund’s distribution rate.

Segregation and Coverage Risks

Certain portfolio management techniques, such as, among other things, utilizing tender offer bonds, purchasing securities on a when-issued or delayed delivery basis, entering into swap agreements, futures contracts or other derivative transactions, or engaging in short sales, may be considered senior securities unless steps are taken to segregate the Fund’s assets or otherwise cover its obligations. To avoid having these instruments considered senior securities, the Fund may segregate liquid assets with a value equal (on a daily mark-to-market basis) to its obligations under these types of leveraged transactions, enter into offsetting transactions or otherwise cover such transactions. See “Use of Leverage” in this prospectus. The Fund may be unable to use such segregated assets for certain other purposes, which could result in the Fund earning a lower return on its portfolio than it might otherwise earn if it did not have to segregate those assets in respect of, or otherwise cover, such portfolio positions. To the extent the Fund’s assets are segregated or committed as cover, it could limit the Fund’s investment flexibility. Segregating assets and covering positions will not limit or offset losses on related positions. In connection with the adoption of Rule 18f-4, the SEC also eliminated the asset segregation framework arising from prior SEC guidance for covering derivatives and certain financial instruments (as described under “Use of Leverage” in the body of this prospectus).

Derivatives Risk

Derivatives are financial contracts whose value depends on, or is derived from, the value of an underlying asset, reference rate or index. The Fund may, but is not required to, utilize a variety of derivative instruments (both long and short positions) for investment or risk management

purposes. The Fund may use derivatives to gain exposure to securities markets in which it may invest (e.g., pending investment of the proceeds of this offering in individual securities, as well as on an ongoing basis). The Fund may also use derivatives to add leverage to its portfolio. See “Principal Risks of the Fund —Leverage Risk.” Derivatives transactions that the Fund may utilize include, but are not limited to, purchases or sales of futures and forward contracts (including foreign currency exchange contracts), call and put options, credit default swaps, total return swaps, basis swaps and other swap agreements. The Fund may also have exposure to derivatives, such as interest rate or credit-default swaps, through investment in credit-linked trust certificates and other securities issued by special purpose or structured vehicles. The Fund may also use derivatives for leverage, in which case their use would involve leveraging risk, and in some cases, may subject the Fund to the potential for unlimited loss. The use of derivatives may cause the Fund’s investment returns to be impacted by the performance of securities the Fund does not own and result in the Fund’s total investment exposure exceeding the value of its portfolio.

The Fund’s use of derivative instruments involves risks different from, or possibly greater than, the risks associated with investing directly in securities and other traditional investments. Derivatives are subject to a number of risks described elsewhere in this prospectus, such as liquidity risk (which may be heightened for highly-customized derivatives), interest rate risk, market risk, credit risk, leveraging risk, counterparty risk, tax risk and management risk, as well as risks arising from changes in applicable requirements. See “Principal Risks of the Fund—Segregation and Coverage Risk.” They also involve the risk of improper valuation, the risk of unfavorable or ambiguous documentation and the risk that changes in the value of a derivative instrument may not correlate perfectly with the underlying asset, rate or index. If the Fund invests in a derivative instrument, the Fund could lose more than the initial amount invested and derivatives may increase the volatility of the Fund, especially in unusual or extreme market conditions.

Also, suitable derivative transactions may not be available in all circumstances and there can be no assurance that the Fund will engage in these transactions to reduce exposure to other risks when that would be beneficial or that, if used, such strategies will be successful. In addition, the Fund’s use of derivatives may increase or accelerate the amount of taxes payable by Common Shareholders. See “Tax Matters.” OTC derivatives are also subject to the risk that a counterparty to the transaction will not fulfill its contractual obligations to the other party, as many of the protections afforded to centrally-cleared derivative transactions might not be available for OTC derivatives. For derivatives traded on an exchange or through a central counterparty, credit risk resides with the Fund’s clearing broker, or the clearinghouse itself, rather than with a counterparty in an OTC derivative transaction. The primary credit risk on deriviatives that are exchange-traded or traded through a central clearing counterparty resides with the Fund’s clearing broker, or the clearinghouse.

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Participation in the markets for derivative instruments involves investment risks and transaction costs to which the Fund may not be subject absent the use of these strategies. The skills needed to successfully execute derivative strategies may be different from those needed for other types of transactions. If the Fund incorrectly forecasts the value and/or creditworthiness of securities, currencies, interest rates, counterparties or other economic factors involved in a derivative transaction, the Fund might have been in a better position if the Fund had not entered into such derivative transaction. In evaluating the risks and contractual obligations associated with particular derivative instruments, it is important to consider that certain derivative transactions may be modified or terminated only by mutual consent of the Fund and its counterparty. Therefore, it may not be possible for the Fund to modify, terminate, or offset the Fund’s obligations or the Fund’s exposure to the risks associated with a derivative transaction prior to its scheduled termination or maturity date, which may create a possibility of increased volatility and/or decreased liquidity to the Fund.

When a derivative is used as a hedge against a position that the Fund holds, any loss generated by the derivative generally should be substantially offset by gains on the hedged investment, and vice versa. Although hedging can reduce or eliminate losses, it can also reduce or eliminate gains. Hedges are sometimes subject to imperfect matching between the derivative and the underlying instrument, and there can be no assurance that the Fund’s hedging transactions will be effective. In such case, the Fund may lose money.

Valuation Risk

The municipal bonds in which the Fund invests may be less liquid and more difficult to value than other types of securities. When market quotations or pricing service prices are not readily available or are deemed to be unreliable, the Fund values its investments at fair value as determined in good faith pursuant to policies and procedures approved by the Board of Trustees. See “Net Asset Value.” Fair value pricing may

require subjective determinations about the value of a security or other asset. As a result, there can be no assurance that fair value pricing will result in adjustments to the prices of securities or other assets, or that fair value pricing will reflect actual market value, and it is possible that the fair value determined for a security or other asset will be materially different from quoted or published prices, from the prices used by others for the same security or other asset and/or from the value that actually could be or is realized upon the sale of that security or other asset.

Counterparty Risk

Confidential Information Access Risk

In managing the Fund, PIMCO may from time to time have the opportunity to receive Confidential Information about the issuers of certain investments, including, without limitation, senior floating rate loans, other loans and related investments being considered for acquisition by the Fund or held in the Fund’s portfolio. For example, an issuer of privately placed loans considered by the Fund may offer to provide PIMCO with financial information and related documentation regarding the issuer that is not publicly available. Pursuant to applicable policies and procedures, PIMCO may (but is not required to) seek to avoid receipt of Confidential Information from the issuer so as to avoid possible restrictions on its ability to purchase and sell investments on behalf of the Fund and other clients to which such Confidential Information relates (e.g., other securities issued by the bank used in the example above). In such circumstances, the Fund (and other PIMCO clients) may be disadvantaged in comparison to other investors,

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including with respect to the price the Fund pays or receives when it buys or sells an investment. Further, PIMCO’s and the Fund’s abilities to assess the desirability of proposed consents, waivers or amendments with respect to certain investments may be compromised if they are not privy to available Confidential Information. PIMCO may also determine to receive such Confidential Information in certain circumstances under its applicable policies and procedures. If PIMCO intentionally or unintentionally comes into possession of Confidential Information, it may be unable, potentially for a substantial period of time, to purchase or sell investments to which such Confidential Information relates.

Private Placements Risk

Risk of Regulatory Changes

Moreover, government regulation may have unpredictable and unintended effects. Many of the changes required by the Dodd-Frank Act could materially impact the profitability of the Fund and the value of assets it holds, expose the Fund to additional costs, require changes to investment practices, and adversely affect the Fund’s ability to pay dividends. For example, the Volcker Rule’s restrictions on proprietary trading have negatively impacted fixed income market making capacity, which resulted in reduced liquidity in certain fixed income markets. Other regulations, such as the Risk Retention Rules, have increased costs for certain securitization transactions. Additional legislative or regulatory actions to address perceived liquidity or other issues in fixed income markets generally, or in particular markets such as the municipal securities market, may alter or impair the Fund’s ability to pursue its investment objectives or utilize certain investment strategies and techniques. While there continues to be uncertainty about the full impact of these and other regulatory changes, it is the case that the

Fund will be subject to a more complex regulatory framework, and may incur additional costs to comply with new requirements as well as to monitor for compliance in the future.

Actions by governmental entities may also impact certain instruments in which the Fund invests. For example, the Fund’s investments (including, but not limited to, repurchase agreements, collateralized loan obligations and mortgage-backed securities), payment obligations and financing terms may rely in some fashion on LIBOR. LIBOR is an average interest rate, determined by the ICE Benchmark Administration, that banks charge one another for the use of short-term money. The United Kingdom’s Financial Conduct Authority (“FCA”), which regulates LIBOR, has announced plans to phase out the use of LIBOR by the end of 2021. On July 27, 2017, the Chief Executive of the FCA announced that after 2021 it will cease its active encouragement of banks to provide the quotations needed to sustain LIBOR due to the absence of an active market for interbank unsecured lending and other reasons. On March 5, 2021, the ICE Benchmark Administration (“IBA”), the administrator of LIBOR, announced that it will cease publication of many of its LIBOR settings after December 31, 2021, and that it will cease publication of certain commonly-used tenors of U.S. dollar LIBOR after June 30, 2023. While the FCA may consult on the issue of requiring the IBA to produce certain LIBOR tenors on a synthetic basis, it has announced that all 35 LIBOR settings will either cease to be provided by any administrator or will no longer be representative as of the dates published by the IBA. The Board of Governors of the Federal Reserve System, Office of the Comptroller of the Currency, and Federal Deposit Insurance Corporation have issued guidance encouraging market participants to adopt alternatives to LIBOR in new contracts as soon as practicable and no later than December 31, 2021. Although the transition process away from LIBOR has become increasingly well-defined in advance of the anticipated discontinuation date, there remains uncertainty regarding the future utilization of LIBOR and the nature of any replacement rate (e.g., the Secured Overnight Financing Rate, which is intended to replace U.S. dollar LIBOR and measures the cost of overnight borrowings through repurchase agreement transactions collateralized with U.S. Treasury securities). Any potential effects of the transition away from LIBOR on the Fund or on certain instruments in which the Fund invests can be difficult to ascertain, and they may vary depending on factors that include, but are not limited to: (i) existing fallback or termination provisions in individual contracts and (ii) whether, how, and when industry participants develop and adopt new reference rates and fallbacks for both legacy and new products and instruments. For example, certain of the Fund’s investments may involve individual contracts that have no existing fallback provision or language that contemplates the discontinuation of LIBOR, and those investments could experience increased volatility or illiquidity as a result of the transition process. In addition, interest rate provisions included in such contracts, or in contracts or other arrangements entered into by the Fund, may need to be renegotiated in contemplation of the transition away from LIBOR. The transition may also result in a reduction in the value of certain instruments held by the Fund, a change in the cost of borrowing or the dividend rate for any preferred shares that may be

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issued by the Fund, or a reduction in the effectiveness of related Fund transactions such as hedges. Any such effects of the transition away from LIBOR, as well as other unforeseen effects, could result in losses to the Fund.

Other Investment Companies Risk

Tax Risk

consist of obligations the interest on which is exempt from regular federal income tax under section 103(a) of the Code as of the close of each quarter of the Fund’s taxable year. If the proportion of taxable investments held by the Fund exceeds 50% of the Fund’s total assets as of the close of any quarter of the Fund’s taxable year, the Fund will not for that taxable year satisfy the general eligibility test that otherwise permits it to pay exempt-interest dividends.

Potential Conflicts of Interest Risk—Allocation of Investment Opportunities

Distribution Risk

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many reasons. There can be no assurance that a change in market conditions or other factors will not result in a change in the Fund’s distribution rate or that the rate will be sustainable in the future.

Securities Lending Risk

Portfolio Turnover Risk

Operational Risk

significant adverse effect on the Fund. While the Fund seeks to minimize such events through controls and oversight, there may still be failures that could cause losses to the Fund.

Market Disruptions Risk

Cyber Security Risk

As the use of technology has become more prevalent in the course of business, the Fund has become potentially more susceptible to operational and information security risks resulting from breaches in cyber security. A breach in cyber security refers to both intentional and unintentional cyber events that may, among other things, cause the Fund to lose proprietary information, suffer data corruption and/or destruction or lose operational capacity, result in the unauthorized release or other misuse of confidential information, or otherwise disrupt normal business operations. Cyber security breaches may involve unauthorized access to the Fund’s digital information systems (e.g., through “hacking” or malicious software coding), but may also result from outside attacks such as denial-of-service attacks (i.e., efforts to make network services unavailable to intended users). In addition, cyber security breaches involving the Fund’s third party service providers (including but not limited to advisers, administrators, transfer agents, custodians, distributors and other third parties), trading counterparties or issuers in which the Fund invests can also subject the Fund to many of the same risks associated with direct cyber security breaches.

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Moreover, cyber security breaches involving trading counterparties or issuers in which the Fund invests could adversely impact such counterparties or issuers and cause the Fund’s investments to lose value.

Like with operational risk in general, the Fund has established business continuity plans and risk management systems designed to reduce the risks associated with cyber security. However, there are inherent limitations in these plans and systems, including that certain risks may not have been identified, in large part because different or unknown threats may emerge in the future. As such, there is no guarantee that such efforts will succeed, especially because the Fund does not directly control the cyber security systems of issuers in which the Fund may invest, trading counterparties or third party service providers to the Fund. There is also a risk that cyber security breaches may not be detected. The Fund and its shareholders could be negatively impacted as a result.

Non-Diversification Risk

Focusing investments in a small number of issuers increases risk. The Fund is “non-diversified,” which means that the Fund may invest a greater percentage of its assets in the securities of a single issuer (such as bonds issued by a particular state) than funds that are “diversified.” A fund that invests in a relatively small number of issuers is more susceptible to risks associated with a single economic, political or regulatory occurrence than a more diversified portfolio might be. Some of those issuers also may present substantial credit or other risks. Similarly, the Fund may be subject to increased economic, business or political risk to the extent that it invests a substantial portion of its assets in a particular currency, in a group of related industries, in a particular issuer, in the bonds of similar projects or in a narrowly defined geographic area outside the U.S. Notwithstanding the Fund’s status as a “non-diversified” investment company under the Act, the Fund intends to qualify as a regulated investment company accorded special tax treatment under the Code, which imposes its own diversification requirements.

Certain Affiliations

generally precluded from effecting certain principal transactions with affiliated brokers, and its ability to purchase securities being underwritten by an affiliated broker or a syndicate including an affiliated broker, or to utilize affiliated brokers for agency transactions, is subject to restrictions. This could limit the Fund’s ability to engage in securities transactions and take advantage of market opportunities.

Anti-Takeover Provisions

The Fund’s Declaration includes provisions that could limit the ability of other entities or persons to acquire control of the Fund or to convert the Fund to open-end status. See “Anti-Takeover and Other Provisions in the Declaration of Trust.”

How the Fund Manages Risk

Hedging and Related Strategies

The Fund may (but is not required to) use various investment strategies to attempt to hedge exposure to reduce the risk of price fluctuations of its portfolio securities, the risk of loss, and to preserve capital. Derivatives strategies and instruments that the Fund may use include: financial futures contracts; short sales; other types of swap agreements or options thereon; options on financial futures; and options based on either an index of municipal securities or taxable debt securities whose prices, PIMCO believes, correlate with the prices of the Fund’s investments. Income earned by the Fund from its hedging and related transactions may be subject to one or more special U.S. federal income tax rules that can affect the amount, timing and/or character of distributions to Common Shareholders. For instance, many hedging activities will be treated as capital gain and, if not offset by net realized capital loss, will be distributed to shareholders in taxable distributions. If effectively used, hedging strategies will offset in varying percentages losses incurred on the Fund’s investments due to adverse interest rate changes. There is no assurance that these hedging strategies will be available at any time or that PIMCO will determine to use them for the Fund or, if used, that the strategies will be successful. PIMCO may determine not to engage in hedging strategies or to do so only in unusual circumstances or market conditions. In addition, the Fund may be subject to certain restrictions on its use of hedging strategies imposed by guidelines of one or more ratings agencies that may issue ratings on any Preferred Shares issued by the Fund.

Management of Investment Portfolio And Capital Structure To Limit Leverage Risk

The Fund may take certain actions if short-term interest rates increase or market conditions otherwise change (or the Fund anticipates such an increase or change) and the Fund’s leverage begins (or is expected) to adversely affect Common Shareholders. In order to attempt to offset such a negative impact of leverage on Common Shareholders, the Fund may shorten the average maturity or duration of its investment portfolio (by investing in short-term, high quality securities or implementing certain hedging strategies). The Fund also may attempt to reduce leverage by redeeming or otherwise purchasing Preferred Shares or by reducing any holdings in other instruments that create leverage. As

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Management of the Fund

Trustees and Officers

The business of the Fund is managed under the direction of the Fund’s Board. The Board is responsible for the management of the Fund, including supervision of the duties performed by the Investment Manager. The Board is currently composed of eight Trustees of the Fund (“Trustees”), six of whom are not “interested persons” of the Fund (as that term is defined by Section 2(a)(19) of the Act). The Trustees meet periodically throughout the year to discuss and consider matters concerning the Fund and to oversee the Fund’s activities, including its investment performance, compliance program and risks associated with its activities. The names and business addresses of the Trustees and officers of the Fund and their principal occupations and other affiliations during the past five years are set forth under “Management of the Fund” in the Statement of Additional Information.

Investment Manager

PIMCO serves as the investment manager for the Fund. Subject to the supervision of the Board, PIMCO is responsible for managing the investment activities of the Fund and the Fund’s business affairs and other administrative matters.

PIMCO may retain affiliates to provide various administrative and other services required by the Fund.

Investment Management Agreement

Pursuant to an investment management agreement between the Investment Manager and the Fund (the “Investment Management Agreement”), the Fund has agreed to pay the Investment Manager an annual fee, payable monthly, in an amount equal to 0.75% of the Fund’s “total managed assets.” Total managed assets means the total assets of the Fund (including assets attributable to any reverse repurchase agreements, dollar rolls, tender option bonds, borrowings and Preferred Shares that may be outstanding, if any) minus accrued liabilities (other than liabilities representing reverse repurchase agreements, dollar rolls, tender option bonds and borrowings). For purposes of calculating “total managed assets,” the liquidation preference of any Preferred Shares outstanding is not considered a liability. By way of clarification, with respect to any reverse repurchase agreement, dollar roll or similar transaction, “total managed assets” includes any proceeds from the sale of an asset of the Fund to a counterparty in such a transaction, in addition to the value of the underlying asset as of the relevant measuring date. Furthermore, to the extent applicable, assets attributable to tender option bonds would be included as assets irrespective of whether or not they are included as assets for financial reporting purposes. However, to the extent the Fund does not contribute municipal bonds to a tender option bond trust but holds residual interests issued by such trust, the tender option bonds outstanding would not be included in the calculation of “total managed assets.” In addition, for purposes of calculating “total managed assets,” the Fund’s derivative investments will be valued based on their market value.

Pursuant to the Investment Management Agreement, PIMCO shall provide to the Fund investment guidance and policy direction in connection with the management of the Fund, including oral and written research, analysis, advice and statistical and economic data and information. In addition, under the terms of the Investment Management Agreement, subject to the general supervision of the Board of Trustees, PIMCO provides or causes to be furnished all supervisory and administrative and other services reasonably necessary for the operation of the Fund under the unified management fee, including but not limited to the supervision and coordination of matters relating to the operation of the Fund, including any necessary coordination among the custodian, transfer agent, dividend disbursing agent, and recordkeeping agent (including pricing and valuation of the Fund), accountants, attorneys, and other parties performing services or operational functions for the Fund; the provision of adequate personnel, office space, communications facilities, and other facilities necessary for the effective supervision and administration of the Fund, as well as the services of a sufficient number of persons competent to perform such supervisory and administrative and clerical functions as are necessary for compliance with federal securities laws and other applicable laws; the maintenance of the books and records of the Fund; the preparation of all federal, state, local and foreign tax returns and reports for the Fund; the preparation, filing and distribution of any proxy materials (except as provided below), periodic reports to shareholders and other regulatory filings; the provision of administrative services to shareholders for the Fund including the maintenance of a shareholder information telephone number, the provision of certain statistical information and performance of the Fund, an internet website (if requested), and maintenance of privacy protection systems and procedures; the preparation and filing of such registration statements and other documents with such authorities as may be required to register a new class of shares of the Fund; the taking of other such actions as may be required by applicable law (including establishment and maintenance of a compliance program for the Fund); and the provision of administrative services to shareholders as necessary, including: the maintenance of a shareholder call center; shareholder transaction processing; the provision of certain

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statistical information and performance of the Fund; a web servicing platform and internet website; access by PIMCO representatives to databases to assist with shareholder inquiries and reports; oversight of anti-money laundering monitoring systems and procedures; and processing of client registration applications.

Under the Investment Management Agreement, PIMCO will pay all expenses incurred by it in connection with its obligations under the Investment Management Agreement with respect to the Fund, with the exception of certain expenses that are assumed by the Fund pursuant to the Investment Management Agreement. In addition, PIMCO is responsible for the following costs expenses: expenses of all audits by the Fund’s independent public accountants; expenses of the Fund’s transfer agent, registrar, dividend disbursing agent, and recordkeeping agent; expenses and fees paid to agents and intermediaries for sub-transfer agency, sub-accounting and other shareholder services on behalf of shareholders of Shares of the Fund (or Shares of a particular Share class) held through omnibus and networked, record shareholder accounts (together, “Sub-Transfer Agency Expenses”), except where Sub-Transfer Agency Expenses are paid pursuant to a Rule 12b-1 or similar plan adopted by the Board of Trustees of the Fund; expenses of the Fund’s custodial services, including any recordkeeping services provided by the custodian; expenses of obtaining quotations for calculating the value of the Fund’s net assets; expenses of maintaining the Fund’s tax records; certain expenses and fees, including legal fees, incident to meetings of the Fund’s shareholders; certain expenses associated with the preparation, printing and distribution of the Fund’s prospectuses, notices and proxy statements, press releases and reports to existing shareholders; certain expenses associated with the preparation and filing of registration statements and updates thereto and reports with regulatory bodies; expenses associated with the maintenance of the Fund’s existence and qualification to do business; expenses (including registration fees) of issuing, redeeming and repurchasing (including expenses associated with the Fund’s repurchases pursuant to Rule 23c-3 under the Act); expenses associated with registering and qualifying for sale Common Shares with federal and state securities authorities following the initial registration of its Common Shares under the 1933 Act (i.e., that are not organizational and offering expenses of the Fund specified below) and following any registration of a new class of shares of the Fund subsequent to its initial registration; and the expense of qualifying and listing existing Common Shares with any securities exchange or other trading system; the Fund’s ordinary legal fees, including the legal fees that arise in the ordinary course of business for a Massachusetts business trust, registered as a closed-end management investment company and, as applicable, that operates as an “interval fund” pursuant to Rule 23c-3 under the Act, or that is listed for trading with a securities exchange or other trading system; costs of printing certificates representing Common Shares of the Fund, if any; the Fund’s pro rata portion of the fidelity bond required by Section 17(g) of the Act, or other insurance premiums; and organizational and offering expenses, including registration (including share registration) fees, legal, marketing, printing, accounting and other expenses, in connection with any registration of a new class of shares of the Fund subsequent to its initial registration.

The Fund (and not PIMCO) is responsible for certain fees and expenses that are not covered by the unified management fee under the Investment Management Agreement. These include salaries and other compensation or expenses, including travel expenses, of any of the Fund’s executive officers and employees, if any, who are not officers, directors, shareholders, members, partners or employees of PIMCO or its subsidiaries or affiliates; taxes and governmental fees, if any, levied against the Fund; brokerage fees and commissions, and other portfolio transaction expenses incurred by or for the Fund (including, without limitation, fees and expenses of outside legal counsel or third-party consultants retained in connection with reviewing, negotiating and structuring specialized loans and other investments made by the Fund, and any costs associated with originating loans, asset securitizations, alternative lending-related strategies and so-called “broken-deal costs” (e.g., fees, costs, expenses and liabilities, including, for example, due diligence-related fees, costs, expenses and liabilities, with respect to unconsummated investments)); expenses of the Fund’s securities lending (if any), including any securities lending agent fees, as governed by a separate securities lending agreement; costs, including interest expenses, of borrowing money or engaging in other types of leverage financing including, without limitation, through the use by the Fund of reverse repurchase agreements, dollar rolls, bank borrowings, credit facilities and tender option bonds; costs, including dividend and/or interest expenses and other costs (including, without limitation, offering and related legal costs, fees to brokers, fees to auction agents, fees to transfer agents, fees to ratings agencies and fees to auditors associated with satisfying ratings agency requirements for Preferred Shares or other securities issued by the Fund and other related requirements in the Fund’s organizational documents) associated with the Fund’s issuance, offering, redemption and maintenance of Preferred Shares, commercial paper or other instruments (such as the use of reverse repurchase agreements, dollar rolls, bank borrowings, credit facilities and tender option bonds) for the purpose of incurring leverage; fees and expenses of any underlying funds or other pooled vehicles in which the Fund invests; dividend and interest expenses on short positions taken by the Fund; fees and expenses, including travel expenses, and fees and expenses of legal counsel retained for their benefit, of Trustees who are not officers, employees, partners, shareholders or members of PIMCO or its subsidiaries or affiliates; extraordinary expenses, including extraordinary legal expenses, as may arise, including, without limitation, expenses incurred in connection with litigation, proceedings, other claims, and the legal obligations of the Fund to indemnify its Trustees, officers, employees, shareholders, distributors, and agents with respect thereto; fees and expenses, including legal, printing and mailing, solicitation and other fees and expenses associated with and incident to shareholder meetings and proxy solicitations involving contested elections of Trustees, shareholder proposals or other non-routine matters that are not initiated or proposed by Fund management; organizational and offering expenses of the Fund, including registration (including Share registration fees), legal, marketing, printing, accounting and other expenses, associated with organizing the Fund in its state of jurisdiction and in connection with the initial registration of the Fund under the Act and the initial registration of its Common Shares under the 1933 Act (i.e., through the effectiveness of the Fund’s initial registration statement on Form N-2) and fees and expenses associated with seeking, applying for and obtaining formal exemptive, no-action and/or other relief from the SEC in connection with the issuance of multiple

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share classes; except as otherwise provided as an expense of PIMCO, any expenses allocated or allocable to a specific class of Common Shares, including without limitation sub-transfer agency expenses and distribution and/or services fees paid pursuant to a Rule 12b-1 or similar plan adopted by the Board of Trustees of the Fund for a particular share class; and expenses of the Fund which are capitalized in accordance with generally accepted accounting principles.

PIMCO may earn a profit on the management fee paid by the Fund. Also, under the terms of the Investment Management Agreement, PIMCO, and not Common Shareholders, would benefit from any price decreases in third-party services, including decreases resulting from an increase in net assets.

Because the management fee received by PIMCO is based on the average daily total managed assets of the Fund, which includes total assets of the Fund (including assets attributable to any reverse repurchase agreements, dollar rolls, tender option bonds, borrowings and Preferred Shares that may be outstanding, if any), PIMCO has a financial incentive for the Fund to utilize reverse repurchase agreements, dollar rolls, tender option bonds and borrowings or to issue Preferred Shares, which may create a conflict of interest between PIMCO, on the one hand, and Common Shareholders, on the other hand.

A discussion of the basis for the Board’s approval of the Fund’s Investment Management Agreement is available in the Fund’s semi-annual report to shareholders for the fiscal half-year ended June 30, 2020.

Expense Limitation Agreement

PIMCO has contractually agreed, through May 2, 2022, to waive its management fee, or reimburse the Fund, to the extent that organizational expenses, pro rata share of expenses related to obtaining or maintaining a Legal Entity Identifier and pro rata Trustees’ fees exceed 0.10% of the Fund’s net assets (the “Expense Limit”). The Expense Limitation Agreement will automatically renew for one-year terms unless PIMCO provides written notice to the Fund at least 30 days prior to the end of the then current term.

Under the Expense Limitation agreement, in any month in which the investment management agreement is in effect, PIMCO is entitled to reimbursement by the Fund of any portion of the management fee reduced as set forth above (the “Reimbursement Amount”) during the previous thirty-six months, provided that such amount paid to PIMCO will not (1) together with any recoupment of organizational expenses, pro rata share of expenses related to obtaining or maintaining a Legal Entity Identifier and pro rata trustee fees or management fees exceed 0.10% of average net assets; (2) exceed the total Reimbursement Amount; or (3) include any amounts previously reimbursed to PIMCO. For the avoidance of doubt, any reimbursement of PIMCO’s management fee pursuant to the expense limitation agreement plus any recoupment of organizational expenses and pro rata Trustees’ fees will not exceed the lesser of (i) the expense limit in effect at the time of waiver or reimbursement and (ii) the expense limit in effect at the time of recoupment

Fee Waiver Agreement

Pursuant to a Management Fee Waiver Agreement between the Fund and PIMCO, PIMCO has contractually agreed, through May 2, 2022, to waive 25% of the management fees it is entitled to receive from the Fund pursuant to the Investment Management Agreement (“Management Fee Waiver Agreement”).

PIMCO’s waiver of management fees under the Management Fee Waiver Agreement is applied first and independently of PIMCO’s obligations under the Expense Limitation Agreement (such that amounts waived pursuant to the Management Fee Waiver Agreement shall not be applied to reduce any waiver or reimbursement obligations PIMCO has under the Expense Limitation Agreement). PIMCO may not seek reimbursement from the Fund with respect to the management fees waived pursuant to the Management Fee Waiver Agreement.

The Management Fee Waiver Agreement will continue through the date set forth above, at which time it will terminate unless otherwise agreed to in writing by the parties. In addition, the Management Fee Waiver Agreement will terminate upon termination of the Investment Management Agreement, or it may be terminated by the Fund, without payment of any penalty, upon notice to PIMCO at its principal place of business.

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PIMCO Flexible Municipal Income Fund

Portfolio Managers

The following individuals share primary responsibility for managing the Fund:

Portfolio Manager(s)	Since	Recent Professional Experience
David Hammer	Inception	Executive Vice President, PIMCO. Mr. Hammer is the head of the municipal bond portfolio management team. He rejoined PIMCO in May 2015 after serving as Managing Director a Head of Municipal Trading, Risk Management and Research at Morgan Stanley, and previously he was a Senior Vice President of PIMCO. Prior to joining PIMCO in 2012, he was an Executive Director for Morgan Stanley, where he served as head of the high yield and distressed municipal bond trading group.
Rachel Betton	Inception	Senior Vice President, PIMCO. Ms. Betton is a municipal bond portfolio manager in the New York office. Prior to joining PIMCO in 2013, she was a municipal high yield and distressed trader at Morgan Stanley. Additionally, she was a public finance banker, focusing on municipal asset-backed securitizations and revenue-backed credits in the Midwest. She has 11 years of investment and financial services experience and holds an undergraduate degree from Wesleyan University.
Amit Arora	August 2019	Executive Vice President, PIMCO. Mr. Arora is a portfolio manager on the global corporate bond team. He was previously a senior member of PIMCO’s global risk management team. Prior to joining PIMCO in 2009, he was an executive director, responsible for credit hybrids and exotics trading, at J.P. Morgan. Mr. Arora was previously with Bear Stearns as a managing director on the structured credit derivatives trading desk, responsible for pricing, trading and hedging of all non-single name credit derivative products in investment grade and high yield credits. Before joining Bear Stearns, he worked on the foreign exchange Treasury desk at Citibank. He has investment experience since 1997 and holds an MBA from NYU Stern School of Business and a bachelor’s degree in mechanical engineering from the Indian Institute of Technology (IIT Bombay). He is a Certified Financial Risk Manager (FRM).

Please see the Statement of Additional Information for additional information about other accounts managed by the portfolio managers, the portfolio managers’ compensation and the portfolio managers’ ownership of shares of the Fund.

Control Persons

A control person is a person who owns, either directly or indirectly, beneficially more than 25% of the voting securities of a company. As of April 1, 2021, the Fund did not know of any person or entity who “controlled” the Fund.

Additional Information

The Trustees are responsible generally for overseeing the management of the Fund. The Trustees authorize the Fund to enter into service agreements with the Investment Manager, the Distributor and other service providers in order to provide, and in some cases authorize service providers to procure through other parties, necessary or desirable services on behalf of the Fund. Shareholders are not intended to be third-party beneficiaries of such service agreements.

Neither this prospectus, the Fund’s Statement of Additional Information, any contracts filed as exhibits to the Fund’s registration statement, nor any other communications or disclosure documents from or on behalf of the Fund creates a contract between a shareholder of the Fund and the Fund, a service provider to the Fund, and/or the Trustees or officers of the Fund. The Trustees may amend this prospectus, the Statement of Additional Information, and any other contracts to which the Fund is a party, and interpret the investment objectives, policies, restrictions and contractual provisions applicable to the Fund without shareholder input or approval, except in circumstances in which shareholder approval is specifically required by law (such changes to fundamental investment policies) or where a shareholder approval requirement is specifically disclosed in this prospectus or the Statement of Additional Information.

53 Prospectus | PIMCO Flexible Municipal Income Fund

Prospectus

Plan of Distribution

PIMCO Investments LLC (the “Distributor”), an affiliate of PIMCO, is the principal underwriter and distributor of the Fund’s Common Shares pursuant to a distribution contract (the “Distribution Contract”) with the Fund. The Distributor, located at 1633 Broadway, New York, New York 10019, is a broker-dealer registered with the SEC and is a member of the Financial Industry Regulatory Authority (“FINRA”). The Distributor is a wholly-owned subsidiary of PIMCO and an indirect subsidiary of Allianz Asset Management. The Distributor does not participate in the distribution of non-PIMCO managed registered fund products.

The Distributor acts as the distributor of Common Shares for the Fund on a best efforts basis, subject to various conditions, pursuant to the terms of the Distribution Contract. The Distributor is not obligated to sell any specific amount of Common Shares of the Fund.

Common Shares of the Fund are continuously offered through the Distributor. As discussed below, the Fund may authorize one or more intermediaries (e.g., broker-dealers and other financial firms) to receive orders on its behalf. The Common Shares will be offered at NAV per share (plus any applicable sales load) calculated each regular business day. Please see “Net Asset Value” below.

The Fund and the Distributor have the sole right to accept orders to purchase Common Shares and reserve the right to reject any order in whole or in part.

The Fund’s Common Shares are not listed for trading on any securities exchange. There is currently no secondary market for the Fund’s Common Shares and the Fund does not anticipate that a secondary market will develop for its Common Shares. Investors should consider Common Shares of the Fund to be an illiquid investment. Neither the Investment Manager nor the Distributor intends to make a market in the Fund’s Common Shares.

The Fund has agreed to indemnify the Distributor and certain of the Distributor’s affiliates against certain liabilities, including certain liabilities arising under the 1933 Act. To the extent consistent with applicable law, the Distributor has agreed to indemnify the Fund and each Trustee against certain liabilities under the 1933 Act, as amended, and in connection with the services rendered to the Fund.

Share Classes

The Fund has adopted a Multi-Class Plan pursuant to Rule 18f-3 under the Act. Although the Fund is not an open-end investment company, it has undertaken to comply with the terms of Rule 18f-3 as a condition of an exemptive order under the Act which permits it to have, among other things, a multi-class structure and distribution and shareholder servicing fees. Under the Multi-Class Plan, shares of each class of the Fund represent an equal pro rata interest in the Fund and, generally, have identical voting, dividend, liquidation, and other rights, preferences, powers, restrictions, limitations, qualifications and terms and conditions, except that: (a) each class has a different designation; (b) each class of shares bears any class-specific expenses; and (c) each class shall have separate voting rights on any matter submitted to shareholders in which the interests of one class differ from the interests of any other class, and shall have exclusive voting rights on any matter submitted to shareholders that relates solely to that class.

The Fund has four separate classes of Common Shares: Institutional Class, Class A-1, Class A-2 and Class A-3. Each share class represents an investment in the same portfolio of investments, but each class has its own expense structure and arrangements for shareholder services or distribution, which allows you to choose the class that best fits your situation and eligibility requirements.

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Institutional Class Common Shares are offered for investment to investors such as pension and profit sharing plans, employee benefit trusts, endowments, foundations, corporations and individuals that can meet the minimum investment amount. Institutional Class Common Shares may also be offered through certain financial firms that charge their customers transaction or other fees with respect to their customers’ investments in the Fund.

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Class A-1, Class A-2 and Class A-3 Common Shares are not available for purchase directly from the Distributor and are primarily offered and sold to retail investors by certain broker-dealers which are members of FINRA and which have agreements with the Distributor to sell Class A-1, Class A-2 and/or Class A-3 Common Shares, but may be made available through other financial firms, including banks and trust companies and to specified benefit plans (as defined below) and other retirement accounts.

Class A-1, Class A-2 and Class A-3 Distribution and Servicing Plans

The Fund has adopted separate Distribution and Servicing Plans for the Class A-1, Class A-2 and Class A-3 Common Shares of the Fund. Each Distribution and Servicing Plan operates in a manner consistent with Rule 12b-1 under the Act, which regulates the manner in which an open-end investment company may directly or indirectly bear the expenses of distributing its shares. Although the Fund is not an open-end investment company, it has undertaken to comply with the terms of Rule 12b-1 as a condition of an exemptive order under the Act which permits it to have, among other things, a multi-class structure and distribution and shareholder servicing fees. Each Distribution and Servicing Plan permits the Fund to compensate the Distributor for providing or procuring through financial firms, distribution, administrative, recordkeeping, shareholder and/or related services with respect to the Class A-1, Class A-2 or Class A-3 Common Shares, as applicable. Most or all of the distribution and/or service fees are

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PIMCO Flexible Municipal Income Fund

paid to financial firms through which Common Shareholders may purchase or hold Class A-1, Class A-2 and Class A-3 Common Shares, as applicable. Because these fees are paid out of the applicable share class’s assets on an ongoing basis, over time they will increase the cost of an investment in Class A-1, Class A-2 or Class A-3 Common Shares and may cost you more than other types of sales charge.

The maximum annual rates at which the distribution and/or servicing fees may be paid under the Distribution and Servicing Plan for Class A-1 Common Shares (calculated as a percentage of the Fund’s average daily net assets attributable to the Class A-1 Common Shares) is 0.50%.

The maximum annual rates at which the distribution and/or servicing fees may be paid under the Distribution and Servicing Plan for Class A-2 Common Shares (calculated as a percentage of the Fund’s average daily net assets attributable to the Class A-2 Common Shares) is 0.50%.

The maximum annual rates at which the distribution and/or servicing fee may be paid under the Distribution and Servicing Plan for Class A-3 Common Shares (calculated as a percentage of the Fund’s average daily net assets attributable to the Class A-3 Common Shares) is 0.75%.

Servicing Arrangements

The Fund’s Common Shares may be available through certain broker-dealers, banks, trust companies, insurance companies and other financial firms that have entered into selling and/or arrangements with respect to the Fund. A financial firm is one that, in exchange for compensation, sells, among other products, registered investment company shares (including the shares offered in this prospectus) or provides services for registered investment company shareholders.

These financial firms provide varying investment products, programs, platforms and accounts, through which investors may purchase Common Shares of the Fund. Selling and/or shareholder servicing arrangements typically include processing orders for shares, generating account and confirmation statements, sub-accounting, account maintenance, tax reporting, collecting and posting distributions to investor accounts and disbursing cash dividends as well as other investment or administrative services required for the particular firm’s products, programs, platform and accounts. These financial firms may impose additional or different conditions than the Fund on purchases of Common Shares. They may also independently establish and charge their customers or program participants transaction fees, account fees and other amounts in connection with purchases of Common Shares in addition to any fees imposed by the Fund. These additional fees may vary and over time could increase the cost of an investment in the Fund and lower investment returns. Each financial firm is responsible for transmitting to its customers and program participants a schedule of any such fees and information regarding any additional or different conditions regarding purchases. Shareholders who are customers of these financial firms or participants in programs serviced by them should contact the financial firm for information regarding these fees and conditions.

PIMCO and/or its affiliates may make payments to financial firms for the shareholder services provided. These payments are made out of PIMCO’s or its affiliates’ resources, including the management fees paid to PIMCO under the Fund’s Investment Management Agreement. The actual services provided by these firms, and the payments made for such services, vary from firm to firm and, in some instances, vary with respect to a single firm according to investment channel. The payments are based on a fixed dollar amount for each account and position maintained by the financial firm and/or a percentage of the value of shares held by investors through the firm. Please see the Statement of Additional Information for more information.

These payments may be material to financial firms relative to other compensation paid by the Fund, PIMCO and/or its affiliates (as applicable) and may be in addition to other fees and payments, such as distribution and/or service fees, revenue sharing or “shelf space” fees and event support, other non-cash compensation and charitable contributions paid to or at the request of such firms (described below). Also, the payments may differ depending on the share class or investment channel and may vary from amounts paid to the Fund’s transfer agent for providing similar services to other accounts. PIMCO and/or its affiliates do not control these financial firms’ provision of the services for which they are receiving payments.

Other Payments to Financial Firms

Some or all of the sales charges, distribution fees and servicing fees described above are paid or “reallowed” to the financial firm, including their financial advisors through which you purchase your shares.

Revenue Sharing/Marketing Support. The Distributor or PIMCO (for purposes of this subsection only, collectively, “PIMCO”) makes payments and provides other incentives to financial firms as compensation for services such as providing the Fund with “shelf space,” or a higher profile for the financial firms’ financial advisors and their customers, placing the Fund on financial firms’ preferred or recommended fund list, granting PIMCO access to the financial firms’ financial advisors and furnishing marketing support and other specified services. These payments may be significant to the financial firms.

A number of factors are considered in determining the amount of these additional payments to financial firms. Such payments may be conditioned upon levels of sales, including the sale of a specified minimum dollar amount of the shares of the Fund and/or other funds sponsored by PIMCO together or a particular class of shares, during a specified period of time. PIMCO also makes payments to one or more financial firms based upon factors such as the amount of assets a financial firm’s clients have invested in the Fund and the quality of the financial firm’s relationship with PIMCO and/or its affiliates.

55 Prospectus | PIMCO Flexible Municipal Income Fund

Prospectus

The additional payments described above are made from PIMCO’s own assets (and sometimes, therefore referred to as “revenue sharing”) pursuant to agreements with financial firms and do not change the price paid by investors for the purchase of the Fund’s shares or the amount the Fund will receive as proceeds from such sales. These payments may be made to financial firms (as selected by PIMCO) that have sold significant amounts of shares of the Fund or other funds sponsored by PIMCO. In certain cases, the payments described in the preceding sentence may be subject to minimum payment levels or vary based on the management fee or total expense ratio of the Fund. In lieu of payments pursuant to the foregoing terms, PIMCO makes, in certain instances, payments of an agreed upon amount which normally will not exceed the amount that would have been payable pursuant to the formula as of the effective date of the agreement.

Ticket Charges. In addition to the payments described above, PIMCO makes payments to financial firms in connection with certain transaction fees (also referred to as “ticket charges”) incurred by the financial firms.

Event Support; Other Non-Cash Compensation; Charitable Contributions. In addition to the payments described above, PIMCO pays and/or reimburses, at its own expense, financial firms for sponsorship and/or attendance at their conferences, seminars or informational meetings (which may include events held through video technology, to the extent permitted by applicable regulation) (“event support”), provides financial firms or their personnel with occasional tickets to events or other entertainment (which, in some instances, is held virtually), meals, and small gifts or pays or provides reimbursement for reasonable travel and lodging expenses for attendees of PIMCO educational events (“other non-cash compensation”) and makes charitable contributions to valid charitable organizations at the request of financial firms (“charitable contributions”) to the extent permitted by applicable law, rules and regulations.

Visits; Training; Education. In addition to the payments described above, wholesale representatives and employees of PIMCO or its affiliates visit financial firms on a regular basis to educate financial advisors and other personnel about the Fund and to encourage the sale or recommendation of Fund shares to their clients. PIMCO may also provide (or compensate consultants or other third parties to provide) other relevant training and education to a financial firm’s financial advisors and other personnel.

Platform Support; Diligence; Leads; Consultant Services. PIMCO also may make payments or reimbursements to financial firms or their affiliated companies, which may be used for their platform development, maintenance, improvement and/or the availability of services including, but not limited to, platform education and communications, relationship management support, development to support new or changing products, trading or order taking platforms and related infrastructure/technology and/or legal, risk management and regulatory compliance infrastructure in support of investment-related products, programs and services and may also result in the Fund receiving greater prominence on a financial firm’s sales platform (collectively, “platform support”), or for various studies, surveys, industry data, research and information about, and contact information for, particular financial advisors who have sold, or may in the future sell, shares of the Fund or other PIMCO-advised funds (i.e., “leads”). PIMCO may also make payments to third party law firms or other service providers that provide certain due diligence services to financial firms with respect to the Fund and/or PIMCO in connection with such financial firm determining whether to include the Fund on its platform. Subject to applicable law, PIMCO and its affiliates may also provide investment advisory services to financial firms and their affiliates and may execute brokerage transactions on behalf of the Fund with such financial firms’ affiliates. These financial firms or their affiliates may, in the ordinary course of their financial firm business, recommend that their clients utilize PIMCO’s investment advisory services or invest in the Fund or in other products sponsored or distributed by PIMCO or its affiliates. In addition, PIMCO may pay investment consultants or their affiliated companies for certain services including, but not limited to, human resources, technology, operations, tax, or audit consulting services and may pay such firms for PIMCO’s attendance at investment forums sponsored by such firms (collectively, “consultant services”). These consultants or their affiliates may, in the ordinary course of their financial firm business, recommend that their clients utilize PIMCO’s investment advisory services or invest in the Fund or in other products sponsored or distributed by PIMCO or its affiliates.

Payments. Payments for items including event support, platform support, leads and consultant services, as well as revenue sharing, are, in certain circumstances, bundled and allocated among these categories in PIMCO’s discretion. The financial firms receiving such bundled payments may characterize or allocate the payments differently from PIMCO’s internal allocation.

If investment advisers, distributors or affiliated persons of registered investment companies make payments and provide other incentives in differing amounts, financial firms and their financial advisors may have financial incentives for recommending a particular fund over other funds. In addition, depending on the arrangements in place at any particular time, a financial firm and its financial advisors also may have a financial incentive for recommending a particular share class over other share classes. A shareholder who holds Fund Common Shares through a financial firm should consult with the shareholder’s financial advisor and review carefully any disclosure by the financial firm as to its compensation received by the financial advisor.

Although the Fund may use financial firms that sell Fund Common Shares to effect transactions for the Fund’s portfolio, the Fund and PIMCO will not consider the sale of Fund Common Shares as a factor when choosing financial firms to effect those transactions.

For further details about payments made by PIMCO to financial firms, please see the Statement of Additional Information.

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PIMCO Flexible Municipal Income Fund

Purchasing Shares

The following section provides basic information about how to purchase Common Shares of the Fund.

The Fund typically does not offer or sell its shares to non-U.S. residents. For purposes of this policy, a U.S. resident is defined as an account with (i) a U.S. address of record and (ii) all account owners residing in the U.S. at the time of sale.

The Fund and the Distributor each reserves the right, in its sole discretion, to suspend the offering of shares of the Fund or to reject any purchase order, in whole or in part, when, in the judgment of management, such suspension or rejection is in the best interests of the Fund.

In the interest of economy and convenience, certificates for shares will not be issued.

If you are eligible to buy Institutional Class Common Shares as well as Class A-1, Class A-2 or Class A-3 Common Shares, you should buy Institutional Class Common Shares because Class A-2 Common Shares may be subject to sales charges, and Class A-1, Class A-2 and Class A-3 Common Shares will pay an annual distribution and/or service fee.

Class A-1, Class A-2 and Class A-3 Common Shares. Eligible investors may purchase Class A-1, Class A-2 and Class A-3 Common Shares through their broker-dealer or other financial firm. Class A-1, Class A-2 and Class A-3 Common Shares are not available for purchase directly from the Distributor.

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Through your broker-dealer or other financial firm. Class A-1, Class A-2 and Class A-3 Common Shares are primarily offered and sold to retail investors by certain broker-dealers that are members of FINRA and that have agreements with the Distributor to offer Class A-1, Class A-2 and/or Class A-3 Common Shares, but may be made available through other financial firms, including banks and trust companies and to specified benefit plans and other retirement accounts. Your broker-dealer or other financial firm may establish different minimum investment requirements than the Fund and may also independently charge you transaction or other fees and additional amounts (which may vary) in return for its services, which will reduce your return. Shares you purchase through your broker-dealer or other financial firm will normally be held in your account with that firm and instructions for buying, selling, exchanging or transferring Class A-1, Class A-2 or Class A-3 Common Shares must be submitted by your broker-dealer or other financial firm on your behalf.

Institutional Class Common Shares.

Eligible investors may purchase Institutional Class Common Shares in the following ways:

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Through your broker-dealer or other financial firm. Institutional Class Common Shares may be offered through certain financial firms that charge their customers transaction or other fees with respect to their customers’ investments in the Fund. Your broker-dealer or other financial firm may establish different minimum investment requirements than the Fund and may also independently charge you transaction or other fees and additional amounts (which may vary) in return for its services, which will reduce your return. Shares you purchase through your broker-dealer or other financial firm will normally be held in your account with that firm. If you purchase shares through a broker-dealer or other financial firm, instructions for buying, selling, exchanging or transferring Institutional Class Common Shares must be submitted by your financial firm or broker-dealer on your behalf.

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Through the Distributor. You should discuss your investment with your financial advisor before you make a purchase to be sure the Fund is appropriate for you. Individual investors who meet the minimum investment amount and wish to invest directly in Institutional Class Common Shares may obtain an Account Application online at pimco.com or by calling 844.312.2113. If you do not list a financial advisor and his/her brokerage firm on the Account Application, the Distributor is designated as the broker of record, but solely for purposes of acting as your agent to purchase shares.

The completed Account Application may be submitted using the following methods:Facsimile: 844.643.0432
Overnight Mail:
PIMCO Interval Funds
C/O DST Systems, Inc.
430 W. 7th Street
Suite 219993
Kansas City, MO 64105-1407
Regular Mail
PIMCO Interval Funds
P.O. Box 219993
Kansas City, MO 64121-9993

57 Prospectus | PIMCO Flexible Municipal Income Fund

Prospectus

E-mail: pimcoaltprocessing@dstsystems.com
For inquiries, please call 844.312.2113.

Payment for the purchase of Common Shares may be made by check payable to the PIMCO Interval Funds and sent to the Regular Mail address above; or by wiring federal funds to:PIMCO Interval Funds
United Missouri Bank
928 Grand Blvd
Kansas City, MO 64106
ABA 101000695
DDA 98-7229-174-3
ACCT: Your PIMCO Account Number
FFC: Shareholder Name and Fund Identifier

Before wiring federal funds, the investor must provide order instructions to the transfer agent by facsimile at 844.643.0432 or by e-mail at pimcoaltprocessing@dstsystems.com. In order to receive the current day’s NAV, order instructions must be received in good order prior to the close of regular trading on the New York Stock Exchange (ordinarily 4:00 p.m., Eastern time) (“NYSE Close”). Instructions must include the name and signature of an appropriate person designated on the Account Application (“Authorized Person”), account name, account number, name of the Fund and dollar amount. Payments received without order instructions could result in a processing delay or a return of wire. Failure to send the accompanying payment on the same day may result in the cancellation of the order.

An investor may place a purchase order for Common Shares without first wiring federal funds if the purchase amount is to be derived from an advisory account managed by PIMCO or one of its affiliates, or from an account with a broker-dealer or other financial firm that has established a processing relationship with the Fund on behalf of its customers

Investment Minimums

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Class A-1, Class A-2 and Class A-3 Common Shares. The following investment minimums apply for purchases of Class A-1, Class A-2 and Class A-3 Common Shares:

Initial Investment	Subsequent Investments
$2,500 per account	$50

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Institutional Class Common Shares. The following investment minimums apply for purchases of Institutional Class Common Shares:

Initial Investment	Subsequent Investments
$1 million per account	None

The initial investment minimums may be modified for certain financial firms that submit orders on behalf of their customers. The Fund or the Distributor may lower or waive the minimum initial investment for certain classes of shares or categories of investors at their discretion. The minimum initial investment may also be modified for the Trustees and certain employees and their extended family members of PIMCO and its affiliates. For these purposes, “extended family members” shall include such person’s spouse or domestic partner, as recognized by applicable state law, children, siblings, current brother/sister-in-laws, parents, and current father/mother-in-laws. Please see the Statement of Additional Information for details.

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Additional Investments. An investor may purchase additional Institutional Class Common Shares of the Fund at any time by sending a facsimile or e-mail as outlined above. If you invest in Common Shares through a broker-dealer, contact your financial firm for information on purchasing additional Common Shares.

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Other Purchase Information. Purchases of the Fund’s Common Shares will be made in full and fractional shares.

Sales Charge - Class A-2 Common Shares

This section includes important information about sales charge reduction programs available to investors in Class A-2 Common Shares of the Fund and describes information or records you may need to provide to the Distributor or your financial firm in order to be eligible for sales charge reduction programs.

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Unless you are eligible for a waiver, the public offering price you pay when you buy Class A-2 Common Shares of the Fund is the NAV of the shares plus an initial sales charge. The initial sales charge varies depending upon the size of your purchase, as set forth below. No sales charge is imposed where Class A-2 Common Shares are issued to you pursuant to the automatic reinvestment of income dividends or capital gains distributions. For investors investing in Class A-2 Common Shares of the Fund through a financial intermediary, it is the responsibility of the financial intermediary to ensure that you obtain the proper “breakpoint” discount.

Because the offering price is calculated to two decimal places, the dollar amount of the sales charge as a percentage of the offering price and your net amount invested for any particular purchase of Fund shares may be higher or lower depending on whether downward or upward rounding was required during the calculation process.

Class A-2 Common Shares are subject to a 3.00% maximum sales charge as a percentage of the offering price (3.09% as a percentage of net amount invested).

Class A-2 Common Shares are subject to the following sales charge:

Your Investment	As a % of Public Offering Price	As a % of Net Amount Invested
Less than $100,000	2.00%(1)	2.04%(1)
$100,000 - $249,999.99	1.00%	1.01%
$250,000 and over	0.00%(2)	0.00%(2)

(1)

Although the Fund is permitted to charge a maximum sales charge of 3.00%, the Fund has elected to currently charge a maximum sales charge of 2.00%.

(2)

As shown, investors that purchase $250,000 or more of the Fund’s Class A-2 Common Shares will not pay any initial sales charge on the purchase. However, unless eligible for a waiver, purchases of $250,000 or more of Class A-2 Common Shares will be subject to an early withdrawal charge of 1.00% if the shares are repurchased during the first 12 months after their purchase. See “Early Withdrawal Charges - Class A-2 Common Shares” and “Sales at Net Asset Value” below.

Investors in the Fund may reduce or eliminate sales charges applicable to purchases of Class A-2 shares through utilization of the Combined Purchase Privilege, Right of Accumulation, Letter of Intent or Reinstatement Privilege. These programs will apply to purchases of closed-end interval funds that PIMCO sponsors currently or in the future (collectively, “Eligible Funds”), which offer Class A-1, Class A-2, Class A-3 and/or Class A-4 Common Shares. These programs are summarized below and described in the Statement of Additional Information. Eligible Funds do not include any open-end mutual funds sponsored by PIMCO.

Combined Purchase Privilege and Right of Accumulation (Breakpoints). A Qualifying Investor (as defined below) may qualify for a reduced sales charge on Class A-2 Common Shares at the breakpoint levels disclosed herein by combining concurrent purchases of the Class A-1, Class A-2, Class A-3 and/or Class A-4 common shares of one or more Eligible Funds into a single purchase (the “Combined Purchase Privilege”). In addition, a Qualifying Investor may obtain a reduced sales charge on Class A-2 Common Shares by adding the purchase value of Class A-1, Class A-2, Class A-3 and/or Class A-4 common shares of an Eligible Fund with the current aggregate net asset value of all Class A-1, Class A-2, Class A-3 and/or Class A-4 common shares of any Eligible Fund held by accounts for the benefit of such Qualifying Investor (the “Right of Accumulation” or “Cumulative Quantity Discount”).

The term “Qualifying Investor” refers to:

an individual, such individual’s spouse or domestic partner, as recognized by applicable state law, or such individual’s children under the age of 21 years (each a “family member”) (including family trust* accounts established by such a family member); or

a trustee or other fiduciary for a single trust (except family trusts* noted above), estate or fiduciary account although more than one beneficiary may be involved; or

an employee benefit plan of a single employer.

For these purposes, a “family trust” is one in which a family member, as defined in section (1) above, or a direct lineal descendant(s) of such person is/are the beneficiary(ies), and such person or another family member, direct lineal ancestor or sibling of such person is/are the trustee(s).

While a shareholder’s positions in Class A-1 and Class A-3 Common Shares are accounted for with respect to reaching a breakpoint level on purchases of Class A-2 or Class A-4 common shares of any Eligible Fund, because neither the Fund nor the Distributor impose an initial sales charge on Class A-1 or Class A-3 Common Shares, the Combined Purchase Privilege and Right of Accumulation programs do not apply to that share class. Class A-1 and Class A-3 Common Shares that count towards reaching a breakpoint level on purchases of Class A-2 or Class A-4 common shares of any Eligible Fund through the Combined Purchase Privilege and Right of Accumulation programs are still subject to transaction or other fees that may be charged by certain financial firms, as those programs do not impact the imposition of such fees.

Letter of Intent. Investors may also obtain a reduced sales charge on purchases of Class A-2 Common Shares of the Fund by means of a written Letter of Intent which expresses an intent to invest not less than $250,000 within a period of 13 months in Class A-1, Class A-2, Class A-3 and/or Class A-4 common shares of any Eligible Fund(s). The maximum intended investment allowable in a Letter of Intent is $250,000. Each purchase of shares under a Letter of Intent will be made at the public offering price or prices applicable at the time of such purchase to a single purchase of the dollar amount

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indicated in the Letter of Intent. The value of the investor’s account(s) linked to a Letter of Intent will be included at the start date of the Letter of Intent. A Letter of Intent is not a binding obligation to purchase the full amount indicated. Shares purchased with the first 5% of the amount indicated in the Letter of Intent will be held in escrow (while remaining registered in your name) to secure payment of the higher sales charges applicable to the shares actually purchased in the event the full intended amount is not purchased. If the full amount indicated is not purchased, a sufficient amount of such escrowed shares will be involuntarily repurchased to pay the additional sales charge applicable to the amount actually purchased, if necessary. Dividends on escrowed shares, whether paid in cash or reinvested in additional Eligible Fund shares, are not subject to escrow. When the full amount indicated has been purchased, the escrow will be released. Repurchases during the Letter of Intent period will not count against the shareholder.

In making computations concerning the amount purchased for purposes of a Letter of Intent, market appreciation in the value of the shareholder’s Class A-1, Class A-2, Class A-3 and/or Class A-4 common shares of Eligible Funds will not be included.

■

Method of Valuation of Accounts. To determine whether a shareholder qualifies for a reduction in sales charge on a purchase of Class A-2 Common Shares of the Fund, the public offering price of the shares is used for purchases relying on the Combined Purchase Privilege or a Letter of Intent and the amount of the total current purchase (including any sales load) plus the NAV (at the close of business on the day of the current purchase) of shares previously acquired is used for the Right of Accumulation.

Reinstatement Privilege. A Class A-2 shareholder who has caused any or all of his or her shares to be repurchased may reinvest all or any portion of the repurchase proceeds in Class A-1, Class A-2, Class A-3 and/or Class A-4 common shares of any Eligible Fund at NAV without any sales charge, provided that such reinvestment is made within 120 calendar days after the repurchase date. The limitations and restrictions of this program are fully described in the Statement of Additional Information.

Sales at Net Asset Value. In addition to the programs summarized above, Class A-2 Common Shares, which are available for purchase only through a broker-dealer or other financial firm, may be sold at NAV without an initial sales charge to certain types of accounts or account holders, including: individuals or accounts having certain relationships with the Fund, certain of its affiliates, certain broker-dealers or the Distributor; purchases made through wrap accounts or certain types of group omnibus plans sponsored by employers, professional or charitable organizations; investors engaging in certain transactions related to IRAs or other qualified retirement plan accounts; investors making certain purchases following the announcement of a Fund or share class liquidation; and any other person for which the Distributor determines that there will be minimal cost borne by the Distributor associated with the sale. Please see the Fund’s Statement of Additional Information for additional details.

Exchanges. Shares of one class of the Fund or one class of common shares of other Eligible Funds may be exchanged for shares of the same class or another class of Common Shares of the Fund without a sales charge. The Fund will only complete an exchange at the direction of a financial intermediary. Contact your financial intermediary to learn more about the details of this exchange feature. See “Exchanging Shares” below for additional information.

Early Withdrawal Charges - Class A-2 Common Shares

Unless you are eligible for a waiver, if you purchase $250,000 or more of Class A-2 Common Shares (and, thus, pay no initial sales charge) of the Fund, you will be subject to a 1% early withdrawal charge (“EWC”) if your Class A-2 Common Shares are repurchased within 12 months of their purchase. The Class A-2 EWC does not apply if you are otherwise eligible to purchase Class A-2 Common Shares without an initial sales charge or are eligible for a waiver of the EWC.

How EWCs will be Calculated

An EWC is imposed on repurchases of Class A-2 Common Shares on the amount of the repurchase which causes the current value of your account for the particular class of Common Shares of the Fund to fall below the total dollar amount of your purchase payments subject to the EWC.

The following rules apply under the method for calculating EWCs:

■

Common Shares acquired through the reinvestment of dividends or capital gains distributions will be repurchased first and will not be subject to any EWC.

■

For the repurchase of all other Common Shares, the EWC will be based on either your original purchase price or the then current NAV of the Common Shares being sold, whichever is lower. To illustrate this point, consider Common Shares purchased at an NAV of $10. If the Fund’s NAV per Common Share at the time of repurchase is $12, the EWC will apply to the purchase price of $10. If the NAV per Common Share at the time of repurchase is $8, the EWC will apply to the $8 current NAV per Common Share.

■

EWCs will be deducted from the proceeds of your repurchase, not from amounts remaining in your account.

■

In determining whether an EWC is payable, it is assumed that you will have repurchased first the lot of Common Shares which will incur the lowest EWC.

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Reductions and Waivers of Initial Sales Charges and EWCs

The initial sales charges and EWCs on Class A-2 Common Shares may be reduced or waived under certain purchase arrangements and for certain categories of investors. See “Sales at Net Asset Value” above for information on such reductions or waivers that may be applicable to Class A-2 initial sales charges.

EWCs on Class A-2 Common Shares may be reduced or waived for repurchases where the shareholder can demonstrate hardship, which shall be determined in the sole discretion of the Distributor, and there will be minimal cost borne by the Distributor associated with the repurchase, which shall be determined in the sole discretion of the Distributor. In addition, investors will not be subject to EWCs for certain transactions where the Distributor did not pay at the time of purchase the amount it normally would have to the broker-dealer.

Required Shareholder Information and Records. In order for investors in Class A-2 Common Shares of the Fund to take advantage of sales charge reductions, an investor or his or her financial firm must notify the Fund that the investor qualifies for such a reduction. If the Fund is not notified that the investor is eligible for these reductions, the Fund will be unable to ensure that the reduction is applied to the investor’s account. An investor may have to provide certain information or records to his or her financial firm or the Fund to verify the investor’s eligibility for breakpoint discounts or sales charge waivers.

An investor may be asked to provide information or records, including account statements, regarding shares of the Fund or other Eligible Funds held in:

■

any account of the investor at another financial firm; and

■

accounts of Qualifying Investors at any financial firm.

Exchanging Shares

Exchanges Across Eligible Funds: Subject to the terms and conditions below, shares of one class of common shares of other Eligible Funds may be exchanged, at the shareholder’s option, for shares of the same class or another class of Common Shares of the Fund. Shareholders may also move their investment in Common Shares of the Fund into shares of the same class or another class of common shares of other Eligible Funds in conjunction with quarterly repurchases made by the Fund. In this case, rather than tendering shares for cash, the shareholder would elect to have the dollar value of those Common Shares accepted for purchases of shares of the other Eligible Funds. Such exchanges for shares of other Eligible Funds must occur in conjunction with quarterly repurchases made by the Fund and will be subject to those repurchase offer risks, such as the risk that shareholders may be unable to liquidate all or a given percentage of their investment in the Fund during a particular repurchase offer, that are described elsewhere in this Prospectus. See “Principal Risks of the Fund - Repurchase Offers Risk.”

The total value of shares being exchanged into the Fund must at least equal the minimum investment requirement applicable to the relevant class of Common Shares of the Fund, and the total value of shares being exchanged out of the Fund into other Eligible Funds must meet the minimum investment requirements of those Eligible Funds, as applicable. Other than exchanges at the direction of a financial intermediary (as described below), shares of the Fund or other Eligible Funds related to such exchanges will be subject to any sales charges, EWCs and/or waivers applicable to such classes of shares.

Intra-Fund Exchanges: Shares of one class of the Fund may be exchanged at any time, at a shareholder’s option, directly for shares of another class of the Fund (an “intra-fund exchange”), subject to the terms and conditions described below and provided that the shareholder for whom the intra-fund exchange is being requested meets the eligibility requirements of the class into which such shareholder seeks to exchange. Additional information regarding the eligibility requirements of different share classes, including investment minimums and intended distribution channels is described under “Purchasing Shares” and “Investment Minimums” above.

Shares of one class of the Fund will be exchanged for shares of a different class of the Fund on the basis of their respective NAVs. Ongoing fees and expenses incurred by a given share class will differ from those of other share classes, and a shareholder receiving new shares in an intra-fund exchange may be subject to higher or lower total expenses following such exchange.

Financial Intermediary-Directed Exchanges: Financial intermediaries may, in connection with a change in a client’s account type, at the direction of a client, or otherwise in accordance with a financial intermediary’s policies and procedures, direct the Fund on behalf of the intermediary’s clients to exchange shares of one class of Common Shares of the Fund for shares of another class of Common Shares of the Fund, or exchange Common Shares of the Fund for the same class or another class of common shares of another Eligible Fund. Any such exchange will not be subject to a sales charge. Class A-1, Class A-2 and Class A-3 Common Shares of the Fund are, however, subject to higher annual operating expenses than Institutional Class Common Shares. See “Summary of Fund Expenses.” The Fund will only complete such an exchange at the direction of a financial intermediary and without making inquiry as to whether the exchange is consistent with the particular intermediary’s policies and procedures or the client’s account type and/or suitability criteria. An investor should contact his or her financial intermediary to learn more about the details of this exchange feature and whether and under what circumstances it may apply in accordance with the investor’s arrangements with the particular intermediary.

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Shares Purchased or Held Through Financial Intermediaries

The availability of sales charge waivers and discounts may depend on the particular financial intermediary or type of account through which you purchase or hold Fund shares. The Fund’s sales charge waivers and discounts disclosed in this prospectus are available for qualifying purchases and are generally available through financial firms unless otherwise specified in Appendix B.

The sales charge waivers, discounts and/or breakpoints available through certain other financial intermediaries are set forth in Appendix B to this prospectus (Financial Firm-Specific Sales Charge Waivers and Discounts), which may differ from those available for purchases made directly from the Distributor or certain other financial firms. Please contact your financial firm for more information regarding applicable sales charge waivers, discounts and/or breakpoints available to you and the financial firm’s related policies and procedures.

While neither the Fund nor the Distributor impose an initial sales charge on Institutional Class, Class A-1 or Class A-3 Common Shares, if you buy Institutional Class, Class A-1 or Class A-3 Common Shares through certain financial firms they may directly charge you transaction or other fees in such amount as they may determine. Please consult your financial firm for additional information.

Signature Validation

When a signature validation is called for, a Medallion signature guarantee or Signature validation program (“SVP”) stamp may be required. A Medallion signature guarantee is intended to provide signature validation for transactions considered financial in nature, and an SVP stamp is intended to provide signature validation for transactions non-financial in nature. In certain situations, a notarized signature may be used instead of a Medallion signature guarantee or an SVP stamp. A Medallion signature guarantee or SVP stamp may be obtained from a domestic bank or trust company, broker, dealer, clearing agency, savings association or other financial institution which is participating in a Medallion program or Signature validation program recognized by the Securities Transfer Association. When a Medallion signature guarantee or SVP stamp is required, signature validations from financial institutions which are not participating in one of these programs will not be accepted. Please note that financial institutions participating in a recognized Medallion program may still be ineligible to provide a signature validation for transactions of greater than a specified dollar amount. The Fund may change the signature validation requirements from time to time upon notice to shareholders, which may be given by means of a new or supplemented prospectus. Shareholders should contact the Fund for additional details regarding the Fund’s signature validation requirements.

In addition, corporations, trusts, and other institutional organizations are required to furnish evidence of the authority of the persons designated on the Account Application to effect transactions for the organization.

Request for Multiple Copies of Shareholder Documents

To reduce expenses, it is intended that only one copy of the Fund’s prospectus and each annual and semi-annual report, when available, will be mailed to those addresses shared by two or more accounts. If you wish to receive individual copies of these documents and your shares are held directly with the Fund, call the Fund at 844.312.2113. You will receive the additional copy within 30 days after receipt of your request by the Fund. Alternatively, if your shares are held through a financial institution, please contact the financial institution directly.

Acceptance and Timing of Purchase Orders

Under normal circumstances, a purchase order received by the Fund or its designee prior to the NYSE Close, on a day the Fund is open for business, together with payment made in one of the ways described above will be effected at that day’s NAV plus any applicable sales charge. An order received after the NYSE Close will be effected at the NAV determined on the next business day. However, orders received by certain retirement plans and other financial firms on a business day prior to the NYSE Close and communicated to the Fund or its designee prior to such time as agreed upon by the Fund and financial firm will be effected at the NAV determined on the business day the order was received by the financial firm. The Fund is “open for business” on each day the NYSE is open for trading, which excludes the following holidays: New Year’s Day, Martin Luther King, Jr. Day, Presidents’ Day, Good Friday, Memorial Day, Independence Day, Labor Day, Thanksgiving Day and Christmas Day. On any day that regular trading on the NYSE closes earlier than scheduled, the Fund reserves the right to: (i) advance the time as of which the NAV is calculated and, therefore, the time by which purchase orders must be received to receive that day’s NAV or (ii) accept purchase orders until, and calculate its NAV as of, the normally scheduled NYSE Close. On any day that the NYSE is closed when it would normally be open for business, the Fund may accept purchase orders until, and calculate its NAV as of, the normally scheduled close of regular trading on the NYSE or such other time that the Fund may determine.

The Fund reserves the right to close if the primary trading markets of the Fund’s portfolio instruments are closed and the Fund’s management believes that there is not an adequate market to meet purchase requests. On any business day when the Securities Industry and Financial Markets Association (“SIFMA”) recommends that the securities markets close trading early, the Fund may close trading early. Purchase orders will be accepted only on days which the Fund is open for business.

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The Fund and the Distributor each reserves the right, in its sole discretion, to accept or reject any order for purchase of Fund Common Shares. The sale of Common Shares may be suspended during any period in which the NYSE is closed other than weekends or holidays, or if permitted by the rules of the SEC, when trading on the NYSE is restricted or during an emergency which makes it impracticable for the Fund to dispose of its securities or to determine fairly the value of its net assets, or during any other period as permitted by the SEC for the protection of investors.

Verification of Identity

To help the federal government combat the funding of terrorism and money laundering activities, federal law requires all financial institutions to obtain, verify and record information that identifies each person that opens a new account, and to determine whether such person’s name appears on government lists of known or suspected terrorists and terrorist organizations. As a result, the Fund must obtain the following information for each person that opens a new account:

Name;

Date of birth (for individuals);

Residential or business street address; and

Social security number, taxpayer identification number, or other identifying number.

Federal law prohibits the Fund and other financial institutions from opening a new account unless they receive the minimum identifying information listed above.

Individuals may also be asked for a copy of their driver’s license, passport or other identifying document in order to verify their identity. In addition, it may be necessary to verify an individual’s identity by cross-referencing the identification information with a consumer report or other electronic database. Additional information may be required to open accounts for corporations and other entities.

After an account is opened, the Fund may restrict your ability to purchase additional Common Shares until your identity is verified. The Fund also may close your account and redeem your shares or take other appropriate action if it is unable to verify your identity within a reasonable time.

Periodic Repurchase Offers

The Fund is a closed-end interval fund and, to provide liquidity and the ability to receive NAV on a disposition of at least a portion of your Common Shares, makes periodic offers to repurchase Common Shares. No shareholder will have the right to require the Fund to repurchase its Common Shares, except as permitted by the Fund’s interval structure. No public market for the Common Shares exists, and none is expected to develop in the future. Consequently, shareholders generally will not be able to liquidate their investment other than as a result of repurchases of their Common Shares by the Fund, and then only on a limited basis.

The Fund has adopted, pursuant to Rule 23c-3 under the Act, a fundamental policy, which cannot be changed without shareholder approval, requiring the Fund to offer to repurchase at least 5% and up to 25% of its Common Shares at NAV on a regular schedule. Although the policy permits repurchases of between 5% and 25% of the Fund’s outstanding Common Shares, for each quarterly repurchase offer, the Fund currently expects to offer to repurchase 10% of the Fund’s outstanding Common Shares at NAV subject to approval of the Board. The schedule requires the Fund to make repurchase offers every three months.

Repurchase Dates

The Fund will make quarterly repurchase offers. Subject to Board approval, Repurchase Request Deadlines are expected to occur each February, May, August and November, and Repurchase Offer Notices are expected to be sent to shareholders each January, April, July and October preceding each such Repurchase Request Deadline. As discussed below, the date on which the repurchase price for Common Shares is determined will occur no later than the 14th day after the Repurchase Request Deadline (or the next business day, if the 14th day is not a business day). A repurchase schedule setting forth each of these dates for the Fund’s current calendar year is available on the Fund’s website at www.pimco.com.

Repurchase Request Deadline

The date by which shareholders wishing to tender Common Shares for repurchase must respond to the repurchase offer will be no more than fourteen days before the Repurchase Pricing Date (defined below). When a repurchase offer commences, the Fund sends, at least 21 days before the Repurchase Request Deadline, written notice to each shareholder setting forth, among other things:

■

The percentage of outstanding Common Shares that the Fund is offering to repurchase and how the Fund will purchase Common Shares on a pro rata basis if the offer is oversubscribed.

■

The date on which a shareholder’s repurchase request is due.

■

The date that will be used to determine the Fund’s NAV applicable to the repurchase offer (the “Repurchase Pricing Date”).

■

The date by which the Fund will pay to shareholders the proceeds from their Common Shares accepted for repurchase.

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■

The NAV of the Common Shares as of a date no more than seven days before the date of the written notice and the means by which shareholders may ascertain the NAV.

■

The procedures by which shareholders may tender their Common Shares and the right of shareholders to withdraw or modify their tenders before the Repurchase Request Deadline.

■

The circumstances in which the Fund may suspend or postpone the repurchase offer.

This notice may be included in a shareholder report or other Fund document. Shareholders that hold shares through a financial intermediary will need to ask their financial intermediary to submit their repurchase requests and tender shares on their behalf. The Repurchase Request Deadline will be strictly observed. If a shareholder’s repurchase request is not submitted to the Fund’s transfer agent in properly completed form by the Repurchase Request Deadline, the shareholder will be unable to sell his or her shares to the Fund until a subsequent repurchase offer, and the shareholder’s request for that offer must be resubmitted. If a shareholder’s Authorized Intermediary will submit his or her repurchase request, the shareholder should submit his or her request to the Authorized Intermediary in the form requested by the Authorized Intermediary sufficiently in advance of the Repurchase Request Deadline to allow the Authorized Intermediary to submit the request to the Fund. If a shareholder’s Authorized Intermediary is unable or fails to submit the shareholder’s request to the Fund in a timely manner, or if the shareholder fails to submit his or her request to the shareholder’s Authorized Intermediary, the shareholder will be unable to sell his or her shares to the Fund until a subsequent repurchase offer, and the shareholder’s request for that offer must be resubmitted.

Shareholders may withdraw or change a repurchase request with a proper instruction submitted in good form at any point before the Repurchase Request Deadline.

Determination of Repurchase Price and Payment for Shares

The Repurchase Pricing Date will occur no later than the 14th day after the Repurchase Request Deadline (or the next business day, if the 14th day is not a business day). The Fund expects to distribute payment to shareholders within three (3) business days after the Repurchase Pricing Date and will distribute such payment no later than seven (7) calendar days after such date. The Fund’s NAV per share may change materially between the date a repurchase offer is mailed and the Repurchase Request Deadline, and it may also change materially between the Repurchase Request Deadline and Repurchase Pricing Date. The method by which the Fund calculates NAV is discussed below under “Net Asset Value.” During the period an offer to repurchase is open, shareholders may obtain the current NAV by visiting www.pimco.com or calling the Fund’s transfer agent at (844) 312-2113.

Suspension or Postponement of Repurchase Offers

The Fund may suspend or postpone a repurchase offer in limited circumstances set forth in Rule 23c-3 under the Act, as described below, but only with the approval of a majority of the Trustees, including a majority of Trustees who are not “interested persons” of the Fund, as defined in the Act. The Fund may suspend or postpone a repurchase offer only: (1) if making or effecting the repurchase offer would cause the Fund to lose its status as a regulated investment company under Subchapter M of the Internal Revenue Code; (2) for any period during which the NYSE or any other market in which the securities owned by the Fund are principally traded is closed, other than customary weekend and holiday closings, or during which trading in such market is restricted; (3) for any period during which an emergency exists as a result of which disposal by the Fund of securities owned by it is not reasonably practicable, or during which it is not reasonably practicable for the Fund fairly to determine the value of its net assets; or (4) for such other periods as the SEC may by order permit for the protection of shareholders of the Fund.

Oversubscribed Repurchase Offers

There is no minimum number of Common Shares that must be tendered before the Fund will honor repurchase requests. However, the Fund’s Trustees set for each repurchase offer a maximum percentage of Common Shares that may be repurchased by the Fund, which is currently expected to be 10% of the Fund’s outstanding Common Shares. In the event a repurchase offer by the Fund is oversubscribed, the Fund may repurchase, but is not required to repurchase, additional Common Shares up to a maximum amount of 2% of the outstanding Common Shares of the Fund. If the Fund determines not to repurchase additional Common Shares beyond the repurchase offer amount, or if shareholders tender an amount of Common Shares greater than that which the Fund is entitled to repurchase, the Fund will repurchase the Common Shares tendered on a pro rata basis.

If any Common Shares that you wish to tender to the Fund are not repurchased because of proration, you will have to wait until the next repurchase offer and resubmit a new repurchase request, and your repurchase request will not be given any priority over other shareholders’ requests. Thus, there is a risk that the Fund may not purchase all of the Common Shares you wish to have repurchased in a given repurchase offer or in any subsequent repurchase offer. In anticipation of the possibility of proration, some shareholders may tender more Common Shares than they wish to have repurchased in a particular quarter, increasing the likelihood of proration.

There is no assurance that you will be able to tender your Common Shares when or in the amount that you desire.

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PIMCO Flexible Municipal Income Fund

Consequences of Repurchase Offers

From the time the Fund distributes or publishes each repurchase offer notification until the Repurchase Pricing Date for that offer, the Fund must maintain liquid assets at least equal to the percentage of its Common Shares subject to the repurchase offer. For this purpose, “liquid assets” means assets that may be sold or otherwise disposed of in the ordinary course of business, at approximately the price at which the Fund values them, within the period between the Repurchase Request Deadline and the repurchase payment deadline, or which mature by the repurchase payment deadline. The Fund is also permitted to borrow up to the maximum extent permitted under the Act to meet repurchase requests.

If the Fund borrows to finance repurchases, interest on that borrowing will negatively affect shareholders who do not tender their Common Shares by increasing the Fund’s expenses and reducing any net investment income. There is no assurance that the Fund will be able sell a significant amount of additional Common Shares so as to mitigate these effects.

These and other possible risks associated with the Fund’s repurchase offers are described under “Principal Risks of Investment in the Fund — Repurchase Offers Risk” above. In addition, the repurchase of Common Shares by the Fund will be a taxable event to shareholders, potentially even to those shareholders that do not participate in the repurchase. For a discussion of these tax consequences, see “Tax Matters” below and in the Statement of Additional Information.

Net Asset Value

The NAV of the Fund’s Common Shares is determined by dividing the total value of the Fund’s portfolio investments and other assets, less any liabilities, by the total number of shares outstanding.

On each day that the NYSE is open, the Fund’s Common Shares are ordinarily valued as of the NYSE Close. Information that becomes known to the Fund or its agents after the time as of which NAV has been calculated on a particular day will not generally be used to retroactively adjust the price of a security or the NAV determined earlier that day. If regular trading on the NYSE closes earlier than scheduled, the Fund may calculate its NAV as of the earlier closing time or calculate its NAV as of the normally scheduled close of regular trading on the NYSE for that day. The Fund generally does not calculate its NAV on days on which the NYSE is not open for business. If the NYSE is closed on a day it would normally be open for business, the Fund may calculate its NAV as of the normally scheduled NYSE Close or such other time that the Fund may determine.

For purposes of calculating NAV, portfolio securities and other assets for which market quotes are readily available are valued at market value. Market value is generally determined on the basis of official closing prices or the last reported sales prices, or if no sales are reported, based on quotes obtained from established market makers or prices (including evaluated prices) supplied by the Fund’s approved pricing services, quotation reporting systems and other third-party sources (together, “Pricing Services”). The Fund will normally use pricing data for domestic equity securities received shortly after the NYSE Close and does not normally take into account trading, clearances or settlements that take place after the NYSE Close. A foreign (non-U.S.) equity security traded on a foreign exchange or on more than one exchange is typically valued using pricing information from the exchange considered by PIMCO to be the primary exchange. If market value pricing is used, a foreign (non-U.S.) equity security will be valued as of the close of trading on the foreign exchange, or the NYSE Close, if the NYSE Close occurs before the end of trading on the foreign exchange. Domestic and foreign (non-U.S.) fixed income securities, non-exchange traded derivatives, and equity options are normally valued on the basis of quotes obtained from brokers and dealers or Pricing Services using data reflecting the earlier closing of the principal markets for those securities. Prices obtained from Pricing Services may be based on, among other things, information provided by market makers or estimates of market values obtained from yield data relating to investments or securities with similar characteristics. Certain fixed income securities purchased on a delayed-delivery basis are marked to market daily until settlement at the forward settlement date. Exchange-traded options, except equity options, futures and options on futures are valued at the settlement price determined by the relevant exchange. Swap agreements are valued on the basis of bid quotes obtained from brokers and dealers or market-based prices supplied by Pricing Services. The Fund’s investments in open-end management investment companies, other than exchange-traded funds (“ETFs”) are valued at the NAVs of such investments.

If a foreign (non-U.S.) equity security’s value has materially changed after the close of the security’s primary exchange or principal market but before the NYSE Close, the security may be valued at fair value based on procedures established and approved by the Board. Foreign (non-U.S.) equity securities that do not trade when the NYSE is open are also valued at fair value. With respect to foreign (non-U.S.) equity securities, the Fund may determine the fair value of investments based on information provided by Pricing Services and other third-party vendors, which may recommend fair value or adjustments with reference to other securities, indexes or assets. In considering whether fair valuation is required and in determining fair values, the Fund may, among other things, consider significant events (which may be considered to include changes in the value of U.S. securities or securities indexes) that occur after the close of the relevant market and before the NYSE Close. The Fund may utilize modeling tools provided by third-party vendors to determine fair values of non-U.S. securities. For these purposes, any movement in the applicable reference index or instrument (“zero trigger”) between the earlier close of the applicable foreign market and the NYSE Close may be deemed to be a significant event, prompting the application of the pricing model (effectively resulting in daily fair valuations). Foreign exchanges may permit trading in foreign (non-U.S.) equity securities on days when the Fund is not open for business, which may result in the Fund’s portfolio investments being affected when shareholders are unable to buy or sell shares.

65 Prospectus | PIMCO Flexible Municipal Income Fund

Prospectus

Senior secured floating rate loans for which an active secondary market exists to a reliable degree will be valued at the mean of the last available bid/ask prices in the market for such loans, as provided by a Pricing Service. Senior secured floating rate loans for which an active secondary market does not exist to a reliable degree will be valued at fair value, which is intended to approximate market value. In valuing a senior secured floating rate loan at fair value, the factors considered may include, but are not limited to, the following: (a) the creditworthiness of the borrower and any intermediate participants, (b) the terms of the loan, (c) recent prices in the market for similar loans, if any, and (d) recent prices in the market for instruments of similar quality, rate, period until next interest rate reset and maturity.

Investments valued in currencies other than the U.S. dollar are converted to the U.S. dollar using exchange rates obtained from Pricing Services. As a result, the value of such investments and, in turn, the NAV of the Fund’s shares may be affected by changes in the value of currencies in relation to the U.S. dollar. The value of investments traded in markets outside the United States or denominated in currencies other than the U.S. dollar may be affected significantly on a day that the Fund is not open for business. As a result, to the extent that the Fund holds foreign (non-U.S.) investments, the value of those investments may change at times when shareholders are unable to buy or sell shares and the value of such investments will be reflected in the Fund’s next calculated NAV.

Investments for which market quotes or market-based valuations are not readily available are valued at fair value as determined in good faith by the Board or persons acting at their direction. The Board has adopted methods for valuing securities and other assets in circumstances where market quotes are not readily available, and has delegated to PIMCO the responsibility for applying the fair valuation methods. In the event that market quotes or market-based valuations are not readily available, and the security or asset cannot be valued pursuant to a Board approved valuation method, the value of the security or asset will be determined in good faith by the Valuation Oversight Committee of the Board (“Valuation Oversight Committee”), generally based on recommendations provided by PIMCO. Market quotes are considered not readily available in circumstances where there is an absence of current or reliable market-based data (e.g., trade information, bid/ask information, indicative market quotations (“Broker Quotes”), Pricing Services’ prices), including where events occur after the close of the relevant market, but prior to the NYSE Close, that materially affect the values of the Fund’s securities or assets. In addition, market quotes are considered not readily available when, due to extraordinary circumstances, the exchanges or markets on which the securities trade do not open for trading for the entire day and no other market prices are available. The Board has delegated to PIMCO the responsibility for monitoring significant events that may materially affect the values of the Fund’s securities or assets and for determining whether the value of the applicable securities or assets should be reevaluated in light of such significant events.

When the Fund uses fair valuation to determine the value of a portfolio security or other asset for purposes of calculating its NAV, such investments will not be priced on the basis of quotes from the primary market in which they are traded, but rather may be priced by another method that the Board or persons acting at their direction believe reflects fair value. Fair valuation may require subjective determinations about the value of a security. While the Fund’s policy is intended to result in a calculation of the Fund’s NAV that fairly reflects security values as of the time of pricing, the Fund cannot ensure that fair values determined by the Board or persons acting at their direction would accurately reflect the price that the Fund could obtain for a security if it were to dispose of that security as of the time of pricing (for instance, in a forced or distressed sale). The prices used by the Fund may differ from the value that would be realized if the securities were sold.

Under certain circumstances, the per share NAV of a class of the Fund’s shares may be different from the per share NAV of another class of shares as a result of the different daily expense accruals applicable to each class of shares.

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Distributions

The Fund currently intends to declare income dividends daily and distribute them to Common Shareholders monthly at rates that reflect the past and projected net income of the Fund. Subject to applicable law, the Fund may fund a portion of its distributions with gains from the sale of portfolio securities and other sources. Distributions can only be made from net investment income after paying any accrued dividends to holders of the Preferred Shares. The dividend rate that the Fund pays on its Common Shares may vary as portfolio and market conditions change, and will depend on a number of factors, including without limitation the amount of the Fund’s undistributed net investment income and net short- and long-term capital gains, as well as dividends payable on any Preferred Shares issued by the Fund (including the Preferred Share Gross-Up) and the costs of any other leverage obtained by the Fund (including interest expenses on any tender option bonds, reverse repurchase agreements, dollar rolls and borrowings). The rate of distributions on the Common Shares and the Fund’s dividend policy could change based on a number of factors, including the amount of the Fund’s undistributed net investment income and historical and projected investment income and the amount of the expenses and dividend rates on any outstanding Preferred Shares (and other forms of leverage). For a discussion of factors that may cause the Fund’s income and capital gains (and therefore the dividend) to vary, see “Principal Risks of the Fund.” The Fund intends to distribute each year all of its net investment income and net short-term capital gains. In addition, at least annually, the Fund intends to distribute net realized long-term capital gains not previously distributed, if any. The net investment income of the Fund consists of all income (other than net short-term and long-term capital gains) less all expenses of the Fund (after it pays accrued dividends on the outstanding Preferred Shares). To permit the Fund to maintain more level distributions, the Fund’s distribution rates will be based, in part, on projections as to annual cash available for distribution and, therefore, the distributions paid by the Fund for any particular month may be more or less than the amount of cash available to the Fund for distribution for that monthly period.

The Fund may distribute less than the entire amount of net investment income earned in a particular period. The undistributed net investment income would be available to supplement future distributions. As a result, the distributions paid by the Fund for any particular monthly period may be more or less than the amount of net investment income actually earned by the Fund during the period. Undistributed net investment income will be added to the Fund’s NAV and, correspondingly, distributions from undistributed net investment income will be deducted from the Fund’s NAV.

The Fund’s Preferred Shares pay dividend distributions at a stated rate, which rate will be based generally on the assumption that such dividend distributions will consist entirely of dividends that pass through the character of exempt interest earned by the Fund and are therefore not taxable to shareholders for regular federal income tax purposes (“exempt-interest dividends”). IRS rules nonetheless require a regulated investment company having two or more classes of stock for U.S. federal income tax purposes to characterize amounts distributed as dividends to

each class for the taxable year in accordance with their pro rata share of income or gains of any type. Therefore, the Fund might be required to characterize a portion of dividends paid to preferred shareholders as ordinary income or capital gain dividends. The terms of such Preferred Shares provide further that, in the event less than the entire amount of any particular dividend distribution paid pursuant to the stated rate were to consist of “exempt-interest dividends” (i.e., if a portion of any particular dividend were to derive from ordinary income or capital gain, including short-term capital gain taxable as ordinary income when distributed), the amount of such dividend would increase by an amount (the “Preferred Shareholder Gross-Up”) such that the after-tax amount of such dividend, as increased by the Preferred Shareholder Gross-Up, would equal the total amount the holder of such Preferred Shares would have received if the dividend at the stated rate had consisted entirely of “exempt-interest dividends.” The Preferred Shareholder Gross-Up will be calculated (i) without consideration being given to the time value of money, (ii) assuming that no holder of VMTP Shares or RVMTP Shares is subject to the federal alternative minimum tax, and (iii) assuming that the portion of any dividend distribution (including the amount of the Preferred Shareholder Gross-Up) that is not an exempt interest dividend would be taxable (x), in the hands of the initial purchaser of the VMTP Shares or RVMTP Shares (or certain of its affiliates), at the maximum marginal regular federal corporate income tax rate, and (y), in the hands of any other holder, at the greater of (a) the maximum marginal regular federal individual income tax rate (taking into account the 3.8% Medicare contribution tax on net investment income) applicable to ordinary income or net capital gain, as applicable, or (b) the maximum marginal regular federal corporate income tax rate applicable to ordinary income or net capital gain, as applicable, in each case disregarding the effect of any state or local taxes. Any Preferred Shareholder Gross-Up would reduce the amount that would otherwise be distributable to Common Shareholders.

The tax treatment and characterization of the Fund’s distributions may vary significantly from time to time because of the varied nature of the Fund’s investments. If the Fund estimates that a portion of one of its dividend distributions may be comprised of amounts from sources other than net investment income in accordance with its internal accounting records and related accounting practices, the Fund will notify shareholders of record of the estimated composition of such distribution through a Section 19 Notice. For these purposes, the Fund estimates the source or sources from which a distribution is paid, to the close of the period as of which it is paid, in reference to its internal accounting records and related accounting practices. If, based on such accounting records and practices, it is estimated that a particular distribution does not include capital gains or paid-in surplus or other capital sources, a Section 19 Notice generally would not be issued. It is important to note that differences exist between the Fund's daily internal accounting records and practices, the Fund's financial statements presented in accordance with U.S. GAAP, and reporting practices under income tax regulations. For instance, the Fund's internal accounting records and practices may take into account, among other factors, tax-related characteristics of certain sources of distributions that differ from treatment under U.S. GAAP. Examples of such differences may include,

67 Prospectus | PIMCO Flexible Municipal Income Fund

Prospectus

among others, the treatment of paydowns on mortgage-backed securities purchased at a discount and periodic payments under interest rate swap contracts. Accordingly, among other consequences, it is possible that the Fund may not issue a Section 19 Notice in situations where the Fund's financial statements prepared later and in accordance with U.S. GAAP and/or the final tax character of those distributions might later report that the sources of those distributions included capital gains and/or a return of capital.

The tax characterization of the Fund’s distributions made in a taxable year cannot finally be determined until at or after the end of the year. As a result, there is a possibility that the Fund may make total distributions during a taxable year in an amount that exceeds the Fund’s net investment income and net realized capital gains (as reduced by any capital loss carryforwards) for the relevant year. For example, the Fund may distribute amounts early in the year that are derived from short-term capital gains, but incur net short-term capital losses later in the year, thereby offsetting short-term capital gains out of which distributions have already been made by the Fund. In such a situation, the amount by which the Fund’s total distributions exceed net investment income and net realized capital gains would generally be treated as a tax-free return of capital up to the amount of a shareholder’s tax basis in his or her Common Shares, with any amounts exceeding such basis treated as gain from the sale of Common Shares. In general terms, a return of capital would occur where a Fund distribution (or portion thereof) represents a return of a portion of your investment, rather than net income or capital gains generated from your investment during a particular period. A return of capital is not taxable, but it reduces a shareholder’s tax basis in the Common Shares, thus reducing any loss or increasing any gain on a subsequent taxable disposition by the shareholder of the Common Shares. The Fund will send shareholders detailed tax information with respect to the Fund’s distributions annually. See “Tax Matters.”

The Act currently limits the number of times the Fund may distribute long-term capital gains in any tax year, which may increase the variability of the Fund’s distributions and result in certain distributions being comprised more or less heavily than others of long-term capital gains currently eligible for favorable income tax rates.

Unless a Common Shareholder elects to receive distributions in cash, all distributions of Common Shareholders whose shares are registered with the plan agent will be automatically reinvested in additional Common Shares under the Fund’s Dividend Reinvestment Plan. See “Dividend Reinvestment Plan.”

Although it does not currently intend to do so, the Board may change the Fund’s distribution policy and the amount or timing of distributions, based on a number of factors, including the amount of the Fund’s undistributed net investment income and net short- and long-term capital gains and historical and projected net investment income and net short- and long-term capital gains.

Dividend Reinvestment Plan

Pursuant to the Fund’s dividend reinvestment plan (the “Plan”), all Common Shareholders will have all dividends, including any capital gain dividends, reinvested automatically in additional Common Shares by DST Systems, Inc., as agent for the Common Shareholders (the “Plan Agent”), unless the shareholder elects to receive cash. An election to receive cash may be revoked or reinstated at the option of the shareholder. In the case of record shareholders such as banks, brokers or other nominees that hold Common Shares for others who are the beneficial owners, the Plan Agent will administer the Plan on the basis of the number of Common Shares certified from time to time by the record shareholder as representing the total amount registered in such shareholder’s name and held for the account of beneficial owners who are to participate in the Plan. Shareholders whose shares are held in the name of a bank, broker or nominee should contact the bank, broker or nominee for details.

Common Shares received under the Plan will be issued to you at their NAV on the ex-dividend date; there is no sales or other charge for reinvestment. You are free to withdraw from the Plan and elect to receive cash at any time by giving written notice to the Plan Agent or by contacting your broker or dealer, who will inform the Fund. Your request must be received by the Fund at least ten days prior to the payment date of the distribution to be effective for that dividend or capital gain distribution.

The Plan Agent provides written confirmation of all transactions in the shareholder accounts in the Plan, including information you may need for tax records. Any proxy you receive will include all Common Shares you have received under the Plan.

Automatically reinvested dividends and distributions are taxed in the same manner as cash dividends and distributions. See “Tax Matters.”

The Fund and the Plan Agent reserve the right to amend or terminate the Plan. There is no direct service charge to participants in the Plan; however, the Fund reserves the right to amend the Plan to include a service charge payable by the participants. If the Plan is amended to include such service charges, the Plan Agent will include a notification to registered holders of Common Shares with the Plan Agent. Additional information about the Plan may be obtained from the Plan Agent.

Description of Capital Structure and Shares

The following is a brief description of the capital structure of the Fund. This description does not purport to be complete and is subject to and qualified in its entirety by reference to the Declaration and the Fund’s Bylaws, as amended and restated through the date hereof (the “Bylaws”). The Declaration and Bylaws are each exhibits to the registration statement of which this prospectus is a part.

The Fund is an unincorporated voluntary association with transferable shares of beneficial interest (commonly referred to as a “Massachusetts business trust”) established under the laws of The Commonwealth of Massachusetts by the Declaration. The Declaration provides that the Trustees of the Fund may authorize separate classes of shares of beneficial interest. Preferred Shares (such as the VMTP Shares or RVMTP

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Shares) may be issued in one or more series, with such par value and with such rights as determined by the Board, by action of the Board without the approval of the Common Shareholders.

The following table shows, for each class of authorized securities of the Fund, the amount of (i) shares authorized and (ii) shares outstanding, each as of April 20, 2021:

(1)	(2)	(3)	(4)
Title of Class	Amount Authorized	Amount Held by the Fund for its Account	Amount Outstanding Exclusive of Amount Shown Under(3)
Common Shares	Unlimited	0	37,097,870
VMTP Shares	Unlimited	0	250
Series 2049-A RVMTP Shares	Unlimited	0	250
Series 2050-A RVMTP Shares	Unlimited	0	250
Series 2050-B RVMTP Shares	Unlimited	0	750

Common Shares

The Declaration authorizes the issuance of an unlimited number of Common Shares. The Common Shares will be issued with a par value of $0.00001 per share. The Fund currently has four separate classes of Common Shares: Institutional Class, Class A-1, Class A-2 and Class A-3. An investment in any share class of the Fund represents an investment in the same assets of the Fund. However, the ongoing fees and expenses for each share class may be different. The fees and expenses for the Fund are set forth in “Summary of Fund Expenses” above. Certain share class details are set forth in “Plan of Distribution” above.

Common Shareholders will be entitled to the payment of dividends and other distributions when, as and if declared by the Board after payment of preferential amounts payable to holders of Preferred Shares. All Common Shares have equal rights to the payment of dividends and the distribution of assets upon liquidation after payment of the preferential amounts payable to holders of Preferred Shares. Common Shares will, when issued, be fully paid and, subject to matters discussed in “Anti-Takeover and Other Provisions in the Declaration of Trust,” non-assessable, and will have no pre-emptive or conversion rights or rights to cumulative voting. Upon liquidation of the Fund, after paying or adequately providing for the payment of all liabilities of the Fund and the liquidation preference with respect to any outstanding Preferred Shares, and upon receipt of such releases, indemnities and refunding agreements as they deem necessary for their protection, the Trustees may distribute the remaining assets of the Fund among the Fund’s Common Shareholders.

The Fund does not intend to hold annual meetings of shareholders. If the Fund does hold a meeting of shareholders, Common Shares of the Fund entitle their holders to one vote for each Common Share held; however, separate votes are taken by each class of Common Shares on matters affecting an individual class of Common Shares. Each fractional share shall be entitled to a proportionate fractional vote, except as otherwise provided by the Declaration, Bylaws, or required by applicable

law. So long as any Preferred Shares are outstanding, holders of Preferred Shares will be able to elect two Trustees and vote as a separate class on certain matters.

The Fund will send unaudited reports at least semiannually and audited financial statements annually to all of its Common Shareholders.

The Common Shares are not, and are not expected to be, listed for trading on any national securities exchange nor is there expected to be any secondary trading market in the Common Shares.

Preferred Shares

The Declaration authorizes the issuance of an unlimited number of preferred shares. Preferred shares may be issued in one or more classes or series, with such par value and rights as determined by the Board of Trustees, by action of the Board of Trustees without the approval of the Common Shareholders.

On June 17, 2019, the Fund issued 250 VMTP Shares in a single series, Series 2022. On November 18, 2019, the Fund issued 250 RVMTP Shares in a single series, Series 2049-A. On April 20, 2020, the Fund issued 250 RVMTP shares in a single series, Series 2050-A. On October 1, 2020, the Fund issued 750 RVMTP shares in a single series, Series 2050-B. The VMTP Shares and the RVMTP Shares have a par value of $0.00001 per share and liquidation preference of $100,000 per share. The VMTP Shares and the RVMTP Shares have various rights that were approved by the Board without the approval of Common Shareholders, which are specified in the Fund’s Bylaws. Certain rights, terms and conditions of the VMTP Shares and the RVMTP Shares are summarized below:

Distribution Preference. Any Preferred Shares, including, without limitation, the VMTP Shares and the RVMTP Shares, have complete priority over the Common Shares as to distribution of assets.

VMTP Share Dividends. The dividend rate paid on the VMTP Shares is determined over the course of a seven-day period, which generally commences each Thursday and ends the following Wednesday (the “Rate Period”). The dividends per share for the VMTP Shares for a given Rate Period are dependent on the VMTP Share dividend rate for that Rate Period (the “VMTP Share Dividend Rate”). The VMTP Share Dividend Rate is equal to the greater of (i) the sum of a specified “Index Rate”(1) plus an “Applicable Spread”(2) for the Rate Period, and (ii) the sum of the product of the Index Rate multiplied by the “Applicable Multiplier”(3) for such Rate Period plus 1.00%. The dividend per VMTP Share for the Rate Period is then determined as described in the table below.(4)

Dividend Rate		Rate Period Fraction		VMTP Shares Liquidation Preference		Dividend
		Number of days in the Rate Period (or a part thereof)
Dividend Rate	X	Divided by	X	100,000	=	Dividends per VMTP Share
		Total number of days in the year

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The Index Rate is determined by reference to a weekly, high-grade index comprised of seven-day, tax-exempt variable rate demand notes, generally the Securities Industry and Financial Markets Association Municipal Swap Index.

The Applicable Spread for a Rate Period is a percentage per annum that is based on the long term rating most recently assigned by the applicable ratings agency to the VMTP Shares.

The Applicable Multiplier for a Rate Period is a percentage that is based on the long term rating most recently assigned by the applicable ratings agency to the VMTP Shares.

An increased VMTP Share Dividend Rate could be triggered by the Fund’s failure to comply with certain requirements relating to the VMTP Shares, certain actions taken by the applicable ratings agency or certain determinations regarding the tax status of the VMTP Shares made by a court or other applicable governmental authority. The VMTP Share Dividend Rate will in no event exceed 15% per year.

RVMTP Share Dividends. The dividend rate paid on the RVMTP Shares is also determined over the course of the Rate Period. The dividends per share for the RVMTP Shares for a given Rate Period are dependent on the RVMTP Share dividend rate (the “RVMTP Share Dividend Rate”) for that Rate Period. The RVMTP Share Dividend Rate for Series 2049-A and Series 2050-A is equal to the greater of (i) the sum of a specified “Index Rate” plus an “Applicable Spread”(1) for the Rate Period plus the “Failed Remarketing Spread”(2), and (ii) the sum of (a) the product of the Index Rate multiplied by the “Applicable Multiplier”(3) for such Rate Period plus (b) 1.00% plus (c) the Failed Remarketing Spread. The RVMTP Share Dividend Rate for Series 2050-B is equal to (i) the sum of the Index Rate plus (ii) the Applicable Spread (including the Spread Adjustment (as defined below)) plus (iii) the Failed Remarketing Spread(4). The dividend per RVMTP Share for the Rate Period is then determined as described in the table below.(5)

Dividend Rate		Rate Period Fraction		RVMTP Shares Liquidation Preference		Dividend
		Number of days in the Rate Period (or a part thereof)
Dividend Rate	X	Divided by	X	100,000	=	Dividends per RVMTP Share
		Total number of days in the year

For each series of RVMTP Shares, the Applicable Spread for a Rate Period is a percentage per annum that is based on the long term rating most recently assigned by the applicable ratings agency to such series of the RVMTP Shares, and for Series 2050-B, it is also based on the “Spread Adjustment.”

The Failed Remarketing Spread with respect to a series of RVMTP Shares means (i) for so long as two or more Failed Remarketings have not occurred, 0%, and (ii) following the second occurrence of a Failed Remarketing, 0.15% (for Series 2049-A and Series 2050-A) or 0.25% (for Series 2050-B) multiplied by the number of Failed Remarketings that have occurred after the first Failed Remarketing.A “Failed Remarketing,” with respect to a series of RVMTP Shares, will occur if any RVMTP Shares in such series subject to a Mandatory Tender Event due to the Fund designating a Special Terms Period have not been either retained by the holders or successfully remarketed by the Mandatory Tender Date (each as defined below).

For each series of RVMTP Shares other than the Series 2050-B, the Applicable Multiplier for a Rate Period is a percentage that is based on the long term rating most recently assigned by the applicable ratings agency to such series of the RVMTP Shares.

The “Spread Adjustment” means, (i) for the period from the closing date, October 1, 2020 to and including the date that is six months prior to the then current RVMTP

Early Term Redemption Date (as defined below) (“Rate Period Termination Date”), 0%, and (ii) for the period after the Rate Period Termination Date, 2.00%.

For each series of RVMTP Shares, an increased RVMTP Share Dividend Rate could be triggered by the Fund’s failure to comply with certain requirements relating to such series of the RVMTP Shares, certain actions taken by the applicable ratings agency or certain determinations regarding the tax status of such series of the RVMTP Shares made by a court or other applicable governmental authority. The RVMTP Share Dividend Rate will in no event exceed 15% per year.

RVMTP Special Terms Period. The Fund, at its option, may designate special terms applicable to all of the outstanding RVMTP Shares in a series for a certain period (a “Special Terms Period”) pursuant to a notice of special terms. Such special terms may differ from those provided in the current governing documents of the RVMTP Shares and may include, without limitation, changes to the RVMTP Dividend Rate, dividend payment dates, redemption provisions (including, without limitation, the RVMTP Term Redemption Date or the RVMTP Early Term Redemption Date), required Effective Leverage Ratio, and the Preferred Shareholder Gross-Up (each as defined below); provided that such special terms do not affect the parity ranking of the RVMTP Shares to any other class or series of Preferred Shares then outstanding with respect to dividends or distribution of assets upon dissolution, liquidation, or winding up of the affairs of the Fund. No Special Terms Period with respect to a series of RVMTP Shares will become effective unless certain conditions are satisfied, including that all of the RVMTP Shares in such series are remarketed (except with respect to any RVMTP Shares whose holders have elected to retain their RVMTP Shares for the Special Terms Period). A Special Terms Period will not become effective before the 12-month anniversary (for Series 2049-A and Series 2050-A) or 24-month anniversary (for Series 2050-B) of the date of original issue of the applicable series of RVMTP Shares.

Preferred Shareholder Gross-Up. As noted above, VMTP Shares and RVMTP Shares each pay dividend distributions at stated rates, which rates are based generally on the assumption that such dividend distributions consist entirely of “exempt-interest dividends” (as defined below under “Taxation—Exempt-Interest Dividends”). The terms of the VMTP Shares and the RVMTP Shares provide further that, in the event less than the entire amount of any particular dividend distribution paid pursuant to the stated rate were to consist of “exempt-interest dividends” (i.e., if a portion of any particular dividend were to derive from ordinary income or capital gain, including short-term capital gain taxable as ordinary income when distributed), the amount of such dividend would increase by an amount (the “Preferred Shareholder Gross-Up”) such that the after-tax amount of such dividend, as increased by the Preferred Shareholder Gross-Up, would equal the total amount the holder of such VMTP Shares or RVMTP Shares, as applicable, would have received if the dividend at the stated rate had consisted entirely of “exempt-interest dividends.” The Preferred Shareholder Gross-Up is calculated (i) without consideration being given to the time value of money, (ii) assuming that no holder of VMTP Shares or RVMTP Shares, as applicable, is subject to the federal alternative minimum tax, and (iii) assuming that the portion of any dividend distribution (including the amount of the Preferred Shareholder Gross-Up) that is not an exempt interest dividend would be taxable (x), in the hands of the initial purchaser of the VMTP Shares or RVMTP

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Shares, as applicable, (or certain of its affiliates), at the maximum marginal regular federal corporate income tax rate, and (y) in the case of any other holder, at the greater of (a) the maximum marginal regular federal individual income tax rate (taking into account the 3.8% Medicare contribution tax on net investment income) applicable to ordinary income or net capital gain, as applicable, or (b) the maximum marginal regular federal corporate income tax rate applicable to ordinary income or net capital gain, as applicable, in each case disregarding the effect of any state or local taxes. Any Preferred Shareholder Gross-Up will reduce the amount that would otherwise be distributable to Common Shareholders.

Liquidation Preference. In the event of any voluntary or involuntary liquidation, dissolution or winding up of the affairs of the Fund, holders of VMTP Shares and RVMTP Shares are entitled to receive a preferential liquidating distribution (equal the original purchase price per share of $100,000 plus accumulated and unpaid dividends thereon, whether or not earned or declared) before any distribution of assets is made to Common Shareholders.

Voting Rights. Under the Act, Preferred Shares (including, without limitation, the VMTP Shares and the RVMTP Shares) are required to be voting shares and to have equal voting rights with Common Shares. Except as otherwise indicated in the Prospectus or this Statement of Additional Information, and except as otherwise required by applicable law, Preferred Shares vote together with Common Shareholders as a single class.

In addition, holders of Preferred Shares, including VMTP Shares and RVMTP Shares, voting as a separate class, are entitled to elect two of the Fund’s trustees. The remaining trustees are elected by Common Shareholders and Preferred Shareholders, voting together as a single class. In the unlikely event that two full years of accrued dividends are unpaid on the Preferred Shares, the holders of all outstanding Preferred Shares voting as a separate class, are entitled to elect a majority of the Fund’s trustees until all dividends in arrears with respect to the Preferred Shares have been paid or declared and set apart for payment. In order for the Fund to take certain actions or enter into certain transactions, a separate class vote of Preferred Shareholders is required, in addition to the single class vote of the holders of Preferred Shares and Common Shares.

Act Asset Coverage. In accordance with the Fund’s governing documents and the Act, the Fund is required to maintain certain asset coverage with respect to all outstanding senior securities of the Fund which are stocks for purposes of the Act, including the VMTP Shares and the RVMTP Shares.

Under the Act, the Fund is not permitted to issue preferred shares unless, immediately after such issuance, the value of the Fund’s total net assets (as defined below) is at least 200% of the liquidation value of any outstanding preferred shares and the newly issued preferred shares plus the aggregate amount of any senior securities of the Fund representing indebtedness (i.e., such liquidation value plus the aggregate amount of senior securities representing indebtedness may not exceed 50% of the Fund’s total net assets). In addition, the Fund is

not permitted to declare or pay common share dividends unless immediately thereafter the Fund has a minimum asset coverage ratio of 200% with respect to all outstanding senior securities of the Fund which are stocks for purposes of the Act after deducting the amount of such common share dividends.

In addition, under the terms of the Series 2050-B RVMTP Shares, the Fund must maintain an “asset coverage,” as defined for purposes of Section 18(h) of the Act, of at least 235% with respect to all outstanding preferred shares, including all previously issued outstanding preferred shares (or such other asset coverage as may in the future be specified in or under the Act or by rule, regulation or order of the SEC as the minimum asset coverage for senior securities which are shares of stock of a closed-end investment company).

Additional Investment Limitations. Under the terms of purchase agreements between the Fund and the initial investor in the VMTP Shares and RVMTP Shares, the Fund is subject to various investment limitations. These investment limitations are in addition to, and may be more restrictive than, those to which the Fund is subject in accordance with its investment objectives and policies as described herein and in the Prospectus.

Effective Leverage Ratio Requirement. In accordance with the Bylaws, without the prior written consent of the holders of VMTP Shares and RVMTP Shares, the Fund’s Effective Leverage Ratio may not exceed 42.5% (or 43.5% solely by reason of fluctuations in the market value of the Fund’s portfolio securities) as of the close of business on any business day. If the Fund fails to comply with any additional requirements relating to the calculation of the Effective Leverage Ratio requirement applicable to the VMTP Shares and RVMTP Shares and, in any such case, such failure is not cured as of the close of business on the date that is ten business days following the business day on which such non-compliance is first determined (the “Effective Leverage Ratio Cure Date”), the Fund shall cause the Effective Leverage Ratio to not exceed 42.5% (or 43.5% solely by reason of fluctuations in the market value of the Fund’s portfolio securities), by (i) not later than the close of business on the business day next following the Effective Leverage Ratio Cure Date, engaging in transactions involving or relating to any floating rate securities not owned by the Fund and/or any inverse floating rate securities owned by the Fund, including the purchase, sale or retirement thereof, (ii) to the extent permitted by law, not later than the close of business on the second business day next following the Effective Leverage Ratio Cure Date, causing a notice of redemption to be issued for the redemption of a sufficient number of Preferred Shares, in accordance with the terms of the Preferred Shares, or (iii) engaging in any combination, in the Fund’s discretion, of the actions contemplated by clauses (i) and (ii).

Issuance of Additional Preferred Shares. So long as any Series 2050-B RVMTP Shares are outstanding, the Fund may, without the vote or consent of the holders thereof, authorize, establish and create and issue and sell shares of one or more series of Preferred Shares ranking on a parity with Series 2050-B RVMTP Shares as to the payment of dividends and the distribution of assets upon dissolution, liquidation or the winding up of the affairs of the Fund, in addition to then outstanding

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series of Series 2050-B RVMTP Shares, including additional series of RVMTP Shares, and authorize, issue and sell additional shares of any such Series of Preferred Shares then outstanding or so established or created, including additional series of RVMTP Shares, in each case in accordance with applicable law, provided that the Fund shall, immediately after giving effect to the issuance of such Preferred Shares and to its receipt and application of the proceeds thereof, including to the redemption of Preferred Shares with such proceeds, have “asset coverage,” as defined for the purposes of Section 18(h) of the Act, of at least 250% and an effective leverage ratio not exceeding 40% (calculated according to the terms of the section below entitled “Preferred Shares—Calculation of Effective Leverage Ratio”).

Calculation of Effective Leverage Ratio. For purposes of determining whether the effective leverage requirement discussed above is satisfied, the “Effective Leverage Ratio” on any date shall mean the quotient of: (i) The sum of (A) the aggregate liquidation preference of the Fund’s “senior securities” (as that term is defined in the Act) that are stock for purposes of the Act, excluding, without duplication, (1) any such senior securities for which the Fund has issued a notice of redemption and either has delivered deposit securities or sufficient securities or funds, (as applicable in accordance with the terms of such senior securities) to the paying agent for such senior securities or otherwise has adequate deposit securities or sufficient securities or funds on hand for the purpose of such redemption (as applicable in accordance with the terms of such senior securities) and (2) any such senior securities that are to be redeemed with net proceeds from the sale of the VMTP Shares or RVMTP Shares, for which the Fund has delivered deposit securities or sufficient securities or funds (as applicable in accordance with the terms of such senior securities) to the paying agent for such senior securities or otherwise has adequate deposit securities or sufficient securities or funds on hand (as applicable in accordance with the terms of such senior securities) for the purpose of such redemption; (B) the aggregate principal amount of the Fund’s “senior securities representing indebtedness” (as that term is defined in the Act giving effect to any interpretations thereof by the SEC or its staff); (C) the aggregate principal amount of floating rate securities corresponding to any associated residual floating rate securities not owned by the Fund (less the aggregate principal amount of any such floating rate securities owned by the Fund and corresponding to the associated residual floating rate securities owned by the Fund); and, with respect to Series 2050-B, (D) the aggregate amount of the purchase price component payable for a repurchase under reverse repurchase agreements entered into by the Fund; divided by (ii) the sum of (A) the market value of the Fund’s total assets (including amounts attributable to senior securities, but excluding any assets consisting of deposit securities or funds referred to in clauses (A)(1) and (A)(2) above), less the amount of the Fund’s accrued liabilities (other than liabilities for the aggregate principal amount of “senior securities representing indebtedness” (as that term is defined in the Act, giving effect to any interpretations thereof by the SEC or its staff), including floating rate securities), (B) the aggregate principal amount of floating rate securities not owned by the Fund that correspond to the associated inverse floating rate securities owned by the Fund; and, with respect to Series 2050-B, and (C) the

aggregate amount of the purchase price component payable for a repurchase under reverse repurchase agreements entered into by the Fund.

Ratings Agency Guidelines. The Fund has obtained ratings for the VMTP Shares and the RVMTP Shares from Fitch. For so long as Fitch is rating the VMTP Shares or the RVMTP Shares, the Fund has agreed to adhere to separate guidelines and asset coverage requirements specific to Fitch (“Fitch Preferred Shares Asset Coverage”) as described in Fitch’s published Closed-End Funds and Market Value Structures Rating Criteria (“Fitch Rating Criteria”). These guidelines may be changed by Fitch, in its sole discretion, from time to time. These guidelines impose asset coverage or portfolio composition requirements that may be more stringent than those imposed on the Fund by the Act.

Satisfaction of Fitch Preferred Shares Asset Coverage for the VMTP Shares and Series 2049-A, 2050-A and 2050-B RVMTP Shares requires that the Fund satisfy both a “Fitch Total Overcollateralization Test” (“Fitch Total OC”) and a “Fitch Net Over Collateralization Test” (“Fitch Net OC”, and together with Fitch Total OC, the “Fitch OC Tests”), in each case to be consistent with the then-current rating of the VMTP Shares and the Series 2049-A, 2050-A and 2050-B RVMTP Shares, as applicable, assigned by Fitch using the calculations set forth in the Fitch Rating Criteria, including information therein relating to diversification guidelines as applied to the Fund.

The Fund has agreed that it will adhere to the Fitch OC Tests as described above as of the close of business on the last business day of each month for so long as Fitch is rating the VMTP Shares or the RVMTP Shares, respectively. If the Fund fails to adhere to the Fitch OC Tests as described in the preceding sentence, the Fund will cure such failure (including, without limitation, by causing a notice of redemption to be issued for the redemption of a sufficient number of the Fund’s Preferred Shares) within ten days following the business day on which such failure is first determined.

Fitch may change its rating methodologies for evaluating and providing ratings for shares of closed-end funds at any time and in its sole discretion, perhaps substantially. Such a change could adversely affect the ratings assigned to the Fund’s Preferred Shares, the dividend rates paid thereon, and the expenses borne by the Fund’s Common Shareholders. For instance, on December 4, 2020, Fitch published ratings criteria relating to closed-end fund obligations, including preferred shares, which effectively result in a rating cap of “AA” for debt and preferred stock issued by closed-end funds and a rating cap of “A” for (i) debt and preferred shares issued by closed-end funds exposed to corporate debt, emerging market debt, below-investment-grade and unrated debt, structured securities and equity, (ii) and closed-end funds with material exposure to “BBB” category rated assets. The revised Fitch ratings criteria effectively capped the credit rating of the Fund’s Preferred Shares at “AA”. Following the close of business on April 30, 2021, Fitch downgraded its rating of the Fund’s Preferred Shares from “AAA” to “AA” (except for the Series 2050-B RVMTP Shares, which maintained a “AA” rating) pursuant to the revised ratings criteria and related new rating cap. It is possible for the Fund’s Preferred Shares to

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be further downgraded in the future, which may result in an increase to the dividend rates paid by the Fund on its Preferred Shares and, thereby, the expenses borne by the Fund’s Common Shareholders.

Mandatory Redemptions. The VMTP Shares are subject to a mandatory term redemption date of June 17, 2022, subject to the Fund’s right to extend the term with the consent of the holders of the VMTP Shares (the “VMTP Share Term Redemption Date”). The RVMTP Shares are subject to a mandatory term redemption date of November 18, 2049 (for Series 2049-A), April 20, 2050 (for series 2050-A) and October 1, 2050 (for Series 2050-B), subject to the Fund’s right to extend the term with the consent of the holders of the RVMTP Shares (the “RVMTP Share Term Redemption Date”). There is no assurance that the term of the VMTP Shares or RVMTP Shares will be extended.

In addition, with respect to each series of RVMTP Shares, a “Mandatory Tender Event” will occur on each date that is (i) 20 business days before each three-year anniversary (or, with respect to the Series 2050-B, 42-month anniversary) of the date of original issue of such series of the RVMTP Shares, (ii) the date the Fund delivers a notice designating a Special Terms Period, and (iii) 20 business days before the end of a Special Terms Period (provided that no subsequent Terms Period is designated). If any RVMTP Shares subject to a Mandatory Tender Event upon a three-year anniversary (for Series 2049-A and Series 2050-A) or forty-two month anniversary (for Series 2050-B) of the date of original issue of the RVMTP Shares or upon the end of a Special Terms Period (each, an “RVMTP Early Term Redemption Date”) have not been either retained by the holders or remarketed by the Mandatory Tender Date, the Fund will redeem such RVMTP Shares on the RVMTP Early Term Redemption Date.(1)

With respect to the Mandatory Tender Events described in clauses (i), (ii) and (iii) above, the corresponding “Mandatory Tender Date” means, respectively: (i) the date that is the corresponding three-year anniversary (for Series 2049-A and Series 2050-A) or 42 month anniversary (for series 2050-B) of the date of original issue of such series of RVMTP Shares, (ii) the date on which the related Special Terms Period becomes effective, and (iii) the last day of the related Special Terms Period (subject, in each case, to the holders’ election to retain their RVMTP Shares).

The VMTP Shares and the RVMTP Shares are also subject to mandatory redemption by the Fund, in whole or in part, in certain circumstances, such as the failure by the Fund to comply with asset coverage and/or effective leverage ratio requirements described above (and the failure to cure any such failure within the applicable cure period) or certain actions taken by the applicable ratings agency.

Term Redemption and Early Term Redemption Liquidity Account. At least six months prior to the VMTP Share Term Redemption Date, the RVMTP Share Redemption Date, or the RVMTP Early Term Redemption Date (each, a “Redemption Date”), the Fund will maintain segregated assets of a minimum credit rating quality with a market value equal to at least 110% of the redemption price of all outstanding VMTP Shares or RVMTP Shares to be redeemed until the redemption of all such outstanding VMTP Shares or RVMTP Shares, as applicable. The Fund will include certain liquid and/or highly rated assets in an amount equal to 20% of such segregated assets with five months remaining to the Redemption Date, which amount will increase monthly by 20% and reach 100% with one month remaining to the Redemption Date.

Optional redemption. The Fund may redeem, in whole or from time to time in part, the outstanding VMTP Shares or RVMTP Shares at a redemption price per share equal to (i) the liquidation preference of the VMTP Shares or RVMTP Shares, as applicable, plus (ii) an amount equal to all unpaid dividends and other distributions on such VMTP Shares or RVMTP Shares, as applicable, accumulated from and including the date of issuance to (but excluding) the date of redemption (whether or not earned or declared by the Fund, but without interest thereon) plus (iii) any applicable optional redemption premium.(2)

If the Fund redeems Series 2050-B shares prior to the first anniversary of its closing date, the applicable optional redemption premium will be equal to the product of (i) the Applicable Spread for such RVMTP share in effect on the date of the optional redemption and (ii) the liquidation preference of such RVMTP Share and (iii) a fraction, the numerator of which is the number of calendar days from and including from and including the date of redemption to and excluding the second anniversary of the closing date and the denominator of which is the actual number of calendar days from and including October 1, 2020 to and excluding the second anniversary of the closing date. The applicable option redemption premium for Series 2050-B will be equal to: if (i) If the optional redemption date for Series 2050-B RVMTP Shares occurs on or after the first anniversary of the closing and prior to the second anniversary of its closing date and (X) the Fund does not issue any Preferred Shares before the earlier to occur of the second anniversary of the closing and the date that is thirty (30) calendar days after such optional redemption date, and in effectuating the optional redemption, the Fund redeems a pro rata amount of the Series 2050-B RVMTP Shares (measured by aggregate liquidation preference) that is equivalent to the percentage determined by dividing the total amount of Preferred Shares of the Fund being redeemed on such optional redemption date (measured by aggregate liquidation preference) by the amount of Preferred Shares of the Fund (measured by aggregate liquidation preference) then outstanding that are not then subject to an optional redemption premium or penalty, then zero or (Y) in all other cases, the product of (1) the Applicable Spread for such RVMTP Share in effect on such optional redemption date and (2) the liquidation preference of such RVMTP Share, and (3) a fraction, the numerator of which is the number of calendar days from and including the date of redemption to and excluding the second anniversary of the closing and the denominator of which is the actual number of calendar days from and including October 1, 2020 to and excluding the second anniversary of the closing; or (ii) if either (a) the optional redemption date for such Series 2050-B RVMTP Share either occurs on or after the second anniversary of the closing or (b) the Fund notifies JPMorgan Chase Bank, N.A. (“JPMorgan”) that the optional redemption date has been called in connection with a redemption of common shares as described in Section 6.20 of the Purchase Agreement, then zero. If fewer than all of the outstanding RVMTP Shares of a Series are to be redeemed, the shares of such Series to be redeemed shall be selected either (A) pro rata among the holders of such Series, (B) by lot, or (C) in such other manner as the Board may determine to be fair and equitable.

RVMTP Mandatory Tender. Upon the occurrence of a Mandatory Tender Event with respect to a series of RVMTP Shares, all RVMTP Shares in such series will be subject to mandatory tender (subject to the holders’ election to retain their RVMTP Shares) and the Fund will issue or cause to be issued a notice of mandatory tender to the holders of such RVMTP Shares for remarketing on the Mandatory Tender Date.

Common Share Repurchases. In the event that the Fund notifies JPMorgan that it will repurchase its common shares more frequently than quarterly or repurchase more than 12% of its issued and outstanding Common Shares in connection with a single repurchase offer, the Fund must redeem all of the RVMTP Shares held by JPMorgan in accordance with Section 2.6(c) of the RVMTP Statement (as defined above) by the date of such common share repurchase if JPMorgan

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requests such redemption in writing to the Fund within five (5) business days after receiving such notice.

Anti-Takeover and Other Provisions in the Declaration of Trust

The Declaration and the Bylaws include provisions that could limit the ability of other entities or persons to acquire control of the Fund or to convert the Fund to open-end status.

As described below, the Declaration grants special approval rights with respect to certain matters to members of the Board who qualify as “Continuing Trustees,” which term means a Trustee who either (i) has been a member of the Board for a period of at least thirty-six months (or since the commencement of the Fund’s operations, if less than thirty-six months) or (ii) was nominated to serve as a member of the Board of Trustees by a majority of the Continuing Trustees then members of the Board.

The Declaration requires the affirmative vote or consent of at least seventy-five percent (75%) of the Board of Trustees and holders of at least seventy-five percent (75%) of the Fund’s shares to authorize certain Fund transactions not in the ordinary course of business, including a merger or consolidation or share exchange, any shareholder proposal as to specific investment decisions made or to be with respect to the assets of the Fund or issuance or transfer by the Fund of the Fund’s shares having an aggregate fair market value of $1,000,000 or more (except as may be made pursuant to a public offering, the Fund’s dividend reinvestment plan or upon exercise of any stock subscription rights), unless the transaction is authorized by both a majority of the Trustees and seventy-five percent (75%) of the Continuing Trustees (in which case no shareholder authorization would be required by the Declaration, but may be required in certain cases under the Act). The Declaration also requires the affirmative vote or consent of holders of at least seventy-five percent (75%) of the Fund’s shares entitled to vote on the matter to authorize a conversion of the Fund from a closed-end to an open-end investment company, unless the conversion is authorized by both a majority of the Trustees and seventy-five percent (75%) of the Continuing Trustees (in which case shareholders would have only the minimum voting rights required by the Act with respect to the conversion). Also, the Declaration provides that the Fund may be terminated at any time by vote or consent of at least seventy-five percent (75%) of the Fund’s shares or, alternatively, by vote or consent of both a majority of the Trustees and seventy-five percent (75%) of the Continuing Trustees. See “Anti-Takeover and Other Provisions in the Declaration of Trust” in the Statement of Additional Information for a more detailed summary of these provisions.

The Trustees may from time to time grant other voting rights to shareholders with respect to these and other matters in the Bylaws, certain of which are required by the Act.

The overall effect of these provisions is to render more difficult the accomplishment of a merger or the assumption of control of the Fund by a third party. These provisions also provide, however, the advantage of potentially requiring persons seeking control of the Fund to negotiate with its management regarding the price to be paid and facilitating the

continuity of the Fund’s investment objectives and policies. The Board of Trustees of the Fund has considered the foregoing anti-takeover provisions and concluded that they are in the best interests of the Fund and its shareholders, including Common Shareholders.

The foregoing is intended only as a summary and is qualified in its entirety by reference to the full text of the Declaration and the Bylaws, both of which are on file with the SEC.

Under Massachusetts law, shareholders could, in certain circumstances, be held personally liable for the obligations of the Fund. However, the Declaration contains an express disclaimer of shareholder liability for debts or obligations of the Fund and requires that notice of such limited liability be given in each agreement, obligation or instrument entered into or executed by the Fund or the Trustees. The Declaration further provides for indemnification out of the assets and property of the Fund for all loss and expense of any shareholder held personally liable for the obligations of the Fund. Thus, the risk of a shareholder incurring financial loss on account of shareholder liability is limited to circumstances in which the Fund would be unable to meet its obligations. The Fund believes that the likelihood of such circumstances is remote.

Tax Matters

This section summarizes some of the U.S. federal income tax consequences to U.S. persons of investing in the Fund; the consequences under other tax laws and to non-U.S. shareholders may differ. Shareholders should consult their tax advisors as to the possible application of federal, state, local or non-U.S. income tax laws. Please see the Statement of Additional Information for additional information regarding the tax aspects of investing in the Fund.

Treatment as a Regulated Investment Company

The Fund intends to elect to be treated, and intends each year to qualify and be eligible, to be treated, as a regulated investment company under Subchapter M of the Internal Revenue Code of 1986, as amended (the “Code”). A regulated investment company is not subject to U.S. federal income tax at the corporate level on income and gains from investments that are distributed in a timely manner to shareholders in the form of dividends. The Fund’s failure to qualify as a regulated investment company would result in corporate-level taxation, thereby reducing the return on your investment.

Taxes on Fund Distributions

A shareholder subject to U.S. federal income tax will generally be subject to tax on Fund distributions. For U.S. federal income tax purposes, Fund distributions will generally be taxable to a shareholder as either ordinary income or capital gains. Fund dividends consisting of distributions of investment income generally are taxable to shareholders as ordinary income. The municipal bonds in which the Fund primarily invests are generally issued by states, cities, or a political subdivision, agency, authority or instrumentality of such state or city, the interest on which is generally exempt from regular federal income tax, and Fund distributions of such interest that the Fund properly reports to you as

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“exempt-interest dividends” will generally not be subject to regular federal income tax. An investment in the Fund may result in liability for federal alternative minimum tax for individual shareholders. Distributions of net investment income other than “exempt-interest dividends” will generally be taxable to you as ordinary income.

Federal taxes on Fund distributions of capital gains are determined by how long the Fund owned or is deemed to have owned the investments that generated the capital gains, rather than how long a shareholder has owned the shares. Distributions of net capital gains (that is, the excess of net long-term capital gains over net short-term capital losses, in each case determined with reference to any loss carryforwards) that are properly reported by the Fund as capital gain dividends generally will be treated as long-term capital gains includible in a shareholder’s net capital gains and taxed to individuals at reduced rates. The Fund does not expect a significant portion of its distributions to be treated as long-term capital gains. Distributions of net short-term capital gains in excess of net long-term capital losses generally will be taxable to you as ordinary income. Distributions that the Fund properly reports to you as “qualified dividend income” are taxable at the reduced rates applicable to long-term capital gains provided that both you and the Fund meet certain holding period and other requirements.

The ultimate tax characterization of the Fund’s distributions made in a taxable year cannot be determined finally until after the end of that taxable year. As a result, there is a possibility that the Fund may make total distributions during a taxable year in an amount that exceeds the Fund’s current and accumulated earnings and profits. In that case, the excess generally would be treated as return of capital and would reduce a shareholder’s tax basis in the applicable shares, with any amounts exceeding such basis treated as gain from the sale of such shares. A return of capital is not taxable, but it reduces a shareholder’s tax basis in the shares, thus reducing any loss or increasing any gain on a subsequent taxable disposition by the shareholder of the Common Shares.

Fund distributions are taxable to shareholders as described above even if they are paid from income or gains earned by the Fund before a shareholder’s investment (and thus were included in the price the shareholder paid).

Certain Fund Investments

The Fund’s investments in certain debt instruments could cause the Fund to recognize taxable income in excess of the cash generated by such investments (which may require the Fund to liquidate other investments in order to make required distributions). The Fund does not expect to qualify to pass through tax-exempt dividends to shareholders.

The Fund may at times buy tax-exempt investments at a discount from the price at which they were originally issued, especially during periods of rising interest rates. For federal income tax purposes, some or all of this market discount will be included in the Fund’s ordinary income and will be taxable to you as such when it is distributed.

Taxes When you Dispose of Your Common Shares

Any gain resulting from the disposition of Common Shares that is treated as a sale or exchange for U.S. federal income tax purposes generally will be taxable to shareholders as capital gains for U.S. federal income tax purposes.

Shareholders who offer, and are able to sell all of the Common Shares they hold or are deemed to hold in response to a repurchase offer (as described above) generally will be treated as having sold their shares and generally will recognize a capital gain or loss. In the case of shareholders who tender or are able to sell fewer than all of their shares, it is possible that any amounts that the shareholder receives in such repurchase will be taxable as a dividend to such shareholder. In addition, there is a risk that shareholders who do not tender any of their shares for repurchase, or whose percentage interest in the Fund otherwise increases as a result of the repurchase offer, will be treated for U.S. federal income tax purposes as having received a taxable dividend distribution as a result of their proportionate increase in the ownership of the Fund. The Fund’s use of cash to repurchase shares could adversely affect its ability to satisfy the distribution requirements for treatment as a regulated investment company. The Fund could also recognize income in connection with its liquidation of portfolio securities to fund share repurchases. Any such income would be taken into account in determining whether such distribution requirements are satisfied.

Backup Withholding

The Fund is generally required to withhold and remit to the U.S. Treasury a percentage of the taxable distributions and redemption proceeds paid to any shareholder who fails to properly furnish the Fund with a correct taxpayer identification number, who has under-reported dividend or interest income, or who fails to certify to the Fund that he, she or it is not subject to such withholding.

Custodian and Transfer Agent

The primary custodian of the assets of the Fund is State Street Bank and Trust Company. State Street Bank and Trust Company’s principal business address is One Lincoln Street, Boston, MA 02111. The primary custodian performs custodial and fund accounting services as well as sub-administrative and compliance services on behalf of the Fund. UMB Bank, n.a. also serves as a custodian of the Fund for the purpose of processing investor subscriptions and repurchases. UMB Bank, n.a.’s principal business address is 1010 Grand Boulevard, Kansas City, MO 64106.

DST Systems, Inc., serves as the Fund’s transfer agent, registrar, dividend disbursement agent and shareholder servicing agent, as well as agent for the Fund’s Dividend Reinvestment Plan.

Independent Registered Public Accounting Firm

PwC serves as independent registered public accounting firm for the Fund. PwC provides audit services, tax assistance and consultation in connection with review of SEC and IRS filings.

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Appendix A

Description of Securities Ratings

The Fund’s investments may range in quality from securities rated in the lowest category in which the Fund is permitted to invest to securities rated in the highest category (as rated by Moody’s, Standard & Poor’s or Fitch, or, if unrated, determined by PIMCO to be of comparable quality). The percentage of the Fund’s assets invested in securities in a particular rating category will vary. The following terms are generally used to describe the credit quality of fixed income securities:

High Quality Debt Securities are those rated in one of the two highest rating categories (the highest category for commercial paper) or, if unrated, deemed comparable by PIMCO.

Investment Grade Debt Securities are those rated in one of the four highest rating categories, or if unrated deemed comparable by PIMCO.

Below Investment Grade High Yield Securities (“Junk Bonds”), are those rated lower than Baa by Moody’s, BBB by Standard & Poor’s or Fitch, and comparable securities. They are deemed predominantly speculative with respect to the issuer’s ability to repay principal and interest.

The following is a description of Moody’s, Standard & Poor’s and Fitch’s rating categories applicable to fixed income securities.

Moody’s Investors Service, Inc.

Global Long-Term Rating Scale

Ratings assigned on Moody’s global long-term rating scales are forward-looking opinions of the relative credit risks of financial obligations issued by non-financial corporates, financial institutions, structured finance vehicles, project finance vehicles, and public sector entities. Long-term ratings are assigned to issuers or obligations with an original maturity of one year or more and reflect both on the likelihood of a default or impairment on contractual financial obligations and the expected financial loss suffered in the event of default or impairment.

Aaa: Obligations rated Aaa are judged to be of the highest quality, subject to the lowest level of credit risk.

Aa: Obligations rated Aa are judged to be of high quality and are subject to very low credit risk.

A: Obligations rated A are judged to be upper-medium grade and are subject to low credit risk.

Baa: Obligations rated Baa are judged to be medium-grade and subject to moderate credit risk and as such may possess certain speculative characteristics.

Ba: Obligations rated Ba are judged to be speculative and are subject to substantial credit risk.

B: Obligations rated B are considered speculative and are subject to high credit risk.

Caa: Obligations rated Caa are judged to be speculative of poor standing and are subject to very high credit risk.

Ca: Obligations rated Ca are highly speculative and are likely in, or very near, default, with some prospect of recovery of principal and interest.

C: Obligations rated C are the lowest rated and are typically in default, with little prospect for recovery of principal or interest.

Moody’s appends numerical modifiers 1, 2, and 3 to each generic rating classification from Aa through Caa. The modifier 1 indicates that the obligation ranks in the higher end of its generic rating category; the modifier 2 indicates a mid-range ranking; and the modifier 3 indicates a ranking in the lower end of that generic rating category. Additionally, a “(hyb)” indicator is appended to all ratings of hybrid securities issued by banks, insurers, finance companies, and securities firms.*

* By their terms, hybrid securities allow for the omission of scheduled dividends, interest, or principal payments, which can potentially result in impairment if such an omission occurs. Hybrid securities may also be subject to contractually allowable write-downs of principal that could result in impairment. Together with the hybrid indicator, the long-term obligation rating assigned to a hybrid security is an expression of the relative credit risk associated with that security.

Medium-Term Note Program Ratings

Moody’s assigns provisional ratings to medium-term note (MTN) programs and definitive ratings to the individual debt securities issued from them (referred to as drawdowns or notes).

MTN program ratings are intended to reflect the ratings likely to be assigned to drawdowns issued from the program with the specified priority of claim (e.g., senior or subordinated). To capture the contingent nature of a program rating, Moody’s assigns provisional ratings to MTN programs. A provisional rating is denoted by a (P) in front of the rating.

The rating assigned to a drawdown from a rated MTN or bank/deposit note program is definitive in nature, and may differ from the program rating if the drawdown is exposed to additional credit risks besides the issuer’s default, such as links to the defaults of other issuers, or has other structural features that warrant a different rating. In some circumstances, no rating may be assigned to a drawdown.

Moody’s encourages market participants to contact Moody’s Ratings Desks or visit www.moodys.com directly if they have questions regarding ratings for specific notes issued under a medium-term note program. Unrated notes issued under an MTN program may be assigned an NR (not rated) symbol.

Global Short-Term Rating Scale

Ratings assigned on Moody’s global short-term rating scales are forward-looking opinions of the relative credit risks of financial obligations issued by non-financial corporates, financial institutions, structured finance vehicles, project finance vehicles, and public sector entities. Short-term ratings are assigned to obligations with an original maturity of thirteen months or less and reflect both on the likelihood of a default or impairment on contractual financial obligations and the expected financial loss suffered in the event of default or impairment.

Moody’s employs the following designations to indicate the relative repayment ability of rated issuers:

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P-1: Ratings of Prime-1 reflect a superior ability to repay short-term debt obligations.

P-2: Ratings of Prime-2 reflect a strong ability to repay short-term debt obligations.

P-3: Ratings of Prime-3 reflect an acceptable ability to repay short-term obligations.

NP: Issuers (or supporting institutions) rated Not Prime do not fall within any of the Prime rating categories.

National Scale Long-Term Ratings

Moody’s long-term National Scale Ratings (NSRs) are opinions of the relative creditworthiness of issuers and financial obligations within a particular country. NSRs are not designed to be compared among countries; rather, they address relative credit risk within a given country. Moody’s assigns national scale ratings in certain local capital markets in which investors have found the global rating scale provides inadequate differentiation among credits or is inconsistent with a rating scale already in common use in the country.

In each specific country, the last two characters of the rating indicate the country in which the issuer is located or the financial obligation was issued (e.g., Aaa.ke for Kenya).

Aaa.n: Issuers or issues rated Aaa.n demonstrate the strongest creditworthiness relative to other domestic issuers and issuances.

Aa.n: Issuers or issues rated Aa.n demonstrate very strong creditworthiness relative to other domestic issuers and issuances.

A.n: Issuers or issues rated A.n present above-average creditworthiness relative to other domestic issuers and issuances.

Baa.n: Issuers or issues rated Baa.n represent average creditworthiness relative to other domestic issuers and issuances.

Ba.n: Issuers or issues rated Ba.n demonstrate below-average creditworthiness relative to other domestic issuers and issuances.

B.n: Issuers or issues rated B.n demonstrate weak creditworthiness relative to other domestic issuers and issuances.

Caa.n: Issuers or issues rated Caa.n demonstrate very weak creditworthiness relative to other domestic issuers and issuances.

Ca.n: Issuers or issues rated Ca.n demonstrate extremely weak creditworthiness relative to other domestic issuers and issuances.

C.n: Issuers or issues rated C.n demonstrate the weakest creditworthiness relative to other domestic issuers and issuances.

National Scale Short-Term Ratings

Moody’s short-term NSRs are opinions of the ability of issuers or issuances in a given country, relative to other domestic issuers or issuances, to repay debt obligations that have an original maturity not

exceeding thirteen months. Short-term NSRs in one country should not be compared with short-term NSRs in another country, or with Moody’s global ratings. There are four categories of short-term national scale ratings, generically denoted N-1 through N-4 as defined below.

In each specific country, the first two letters indicate the country in which the issuer is located (e.g., KE-1 through KE-4 for Kenya).

N-1: N-1 issuers or issuances represent the strongest likelihood of repayment of short-term senior unsecured debt obligations relative to other domestic issuers.

N-2: N-2 issuers or issuances represent an above average likelihood of repayment of short-term senior unsecured debt obligations relative to other domestic issuers.

N-3: N-3 issuers or issuances represent an average likelihood of repayment of short-term senior unsecured debt obligations relative to other domestic issuers.

N-4: N-4 issuers or issuances represent a below average likelihood of repayment of short-term senior unsecured debt obligations relative to other domestic issuers.

The short-term rating symbols P-1.za, P-2.za, P-3.za and NP.za are used in South Africa.

Short-Term Obligation Ratings

The Municipal Investment Grade (MIG) scale is used for US municipal cash flow notes, bond anticipation notes and certain other short-term obligations, which typically mature in three years or less. Under certain circumstances, the MIG scale is used for bond anticipation notes with maturities of up to five years.

MIG 1: This designation denotes superior credit quality. Excellent protection is afforded by established cash flows, highly reliable liquidity support, or demonstrated broad-based access to the market for refinancing.

MIG 2: This designation denotes strong credit quality. Margins of protection are ample, although not as large as in the preceding group.

MIG 3: This designation denotes acceptable credit quality. Liquidity and cash-flow protection may be narrow, and market access for refinancing is likely to be less well-established.

SG: This designation denotes speculative-grade credit quality. Debt instruments in this category may lack sufficient margins of protection.

Demand Obligation Ratings

In the case of variable rate demand obligations (VRDOs), a two-component rating is assigned. The components are a long-term rating and a short-term demand obligation rating. The long-term rating addresses the issuer’s ability to meet scheduled principal and interest payments. The short-term demand obligation rating addresses the ability of the issuer or the liquidity provider to make payments associated with the purchase-price-upon-demand feature (“demand feature”) of the VRDO. The short-term demand obligation rating uses the Variable Municipal Investment Grade (VMIG) scale.

April 30, 2021 (as supplemented May 14, 2021) | PROSPECTUS A-2

PIMCO Flexible Municipal Income Fund

VMIG 1: This designation denotes superior credit quality. Excellent protection is afforded by the superior short-term credit strength of the liquidity provider and structural and legal protections that ensure the timely payment of purchase price upon demand.

VMIG 2: This designation denotes strong credit quality. Good protection is afforded by the strong short-term credit strength of the liquidity provider and structural and legal protections that ensure the timely payment of purchase price upon demand.

VMIG 3: This designation denotes acceptable credit quality. Adequate protection is afforded by the satisfactory short-term credit strength of the liquidity provider and structural and legal protections that ensure the timely payment of purchase price upon demand.

SG: This designation denotes speculative-grade credit quality. Demand features rated in this category may be supported by a liquidity provider that does not have a sufficiently strong short-term rating or may lack the structural or legal protections necessary to ensure the timely payment of purchase price upon demand.

Standard & Poor’s Ratings Services

Long-Term Issue Credit Ratings

Issue credit ratings are based, in varying degrees, on S&P Global Ratings’ (“S&P”) analysis of the following considerations:

■

Likelihood of payment—capacity and willingness of the obligor to meet its financial commitments on an obligation in accordance with the terms of the obligation;

■

Nature and provisions of the financial obligation and the promise S&P imputes; and

■

Protection afforded by, and relative position of, the financial obligation in the event of a bankruptcy, reorganization, or other arrangement under the laws of bankruptcy and other laws affecting creditors’ rights.

Issue ratings are an assessment of default risk, but may incorporate an assessment of relative seniority or ultimate recovery in the event of default. Junior obligations are typically rated lower than senior obligations, to reflect lower priority in bankruptcy, as noted above. (Such differentiation may apply when an entity has both senior and subordinated obligations, secured and unsecured obligations, or operating company and holding company obligations.)

Investment Grade

AAA: An obligation rated ‘AAA’ has the highest rating assigned by S&P. The obligor’s capacity to meet its financial commitments on the obligation is extremely strong.

AA: An obligation rated ‘AA’ differs from the highest-rated obligations only to a small degree. The obligor’s capacity to meet its financial commitments on the obligation is very strong.

A: An obligation rated ‘A’ is somewhat more susceptible to the adverse effects of changes in circumstances and economic conditions than obligations in higher-rated categories. However, the obligor’s capacity to meet its financial commitments on the obligation is still strong.

BBB: An obligation rated ‘BBB’ exhibits adequate protection parameters. However, adverse economic conditions or changing circumstances are more likely to weaken the obligor’s capacity to meet its financial commitments on the obligation.

Speculative Grade

Obligations rated ‘BB’, ‘B’, ‘CCC’, ‘CC’, and ‘C’ are regarded as having significant speculative characteristics. ‘BB’ indicates the least degree of speculation and ‘C’ the highest. While such obligations will likely have some quality and protective characteristics, these may be outweighed by large uncertainties or major exposure to adverse conditions.

BB: An obligation rated ‘BB’ is less vulnerable to nonpayment than other speculative issues. However, it faces major ongoing uncertainties or exposure to adverse business, financial, or economic conditions that could lead to the obligor’s inadequate capacity to meet its financial commitments on the obligation.

B: An obligation rated ‘B’ is more vulnerable to nonpayment than obligations rated ‘BB’, but the obligor currently has the capacity to meet its financial commitments on the obligation. Adverse business, financial, or economic conditions will likely impair the obligor’s capacity or willingness to meet its financial commitments on the obligation.

CCC: An obligation rated ‘CCC’ is currently vulnerable to nonpayment, and is dependent upon favorable business, financial, and economic conditions for the obligor to meet its financial commitments on the obligation. In the event of adverse business, financial, or economic conditions, the obligor is not likely to have the capacity to meet its financial commitments on the obligation.

CC: An obligation rated ‘CC’ is currently highly vulnerable to nonpayment. The ‘CC’ rating is used when a default has not yet occurred, but S&P expects default to be a virtual certainty, regardless of the anticipated time to default.

C: An obligation rated ‘C’ is currently highly vulnerable to nonpayment, and the obligation is expected to have lower relative seniority or lower ultimate recovery compared with obligations that are rated higher.

D: An obligation rated ‘D’ is in default or in breach of an imputed promise. For non-hybrid capital instruments, the ‘D’ rating category is used when payments on an obligation are not made on the date due, unless S&P believes that such payments will be made within five business days in the absence of a stated grace period or within the earlier of the stated grace period or 30 calendar days. The ‘D’ rating also will be used upon the filing of a bankruptcy petition or the taking of similar action and where default on an obligation is a virtual certainty, for example due to automatic stay provisions. A rating on an obligation is lowered to ‘D’ if it is subject to a distressed debt restructuring.

NR: This indicates that a rating has not been assigned or is no longer assigned.

Plus (+) or minus (-): The ratings from ‘AA’ to ‘CCC’ may be modified by the addition of a plus (+) or minus (-) sign to show relative standing within the rating categories.

A-3 Prospectus | PIMCO Flexible Municipal Income Fund

Prospectus

Short-Term Issue Credit Ratings

A-1: A short-term obligation rated ‘A-1’ is rated in the highest category by S&P. The obligor’s capacity to meet its financial commitments on the obligation is strong. Within this category, certain obligations are designated with a plus sign (+). This indicates that the obligor’s capacity to meet its financial commitments on these obligations is extremely strong.

A-2: A short-term obligation rated ‘A-2’ is somewhat more susceptible to the adverse effects of changes in circumstances and economic conditions than obligations in higher rating categories. However, the obligor’s capacity to meet its financial commitments on the obligation is satisfactory.

A-3: A short-term obligation rated ‘A-3’ exhibits adequate protection parameters. However, adverse economic conditions or changing circumstances are more likely to weaken an obligor’s capacity to meet its financial commitments on the obligation.

B: A short-term obligation rated ‘B’ is regarded as vulnerable and has significant speculative characteristics. The obligor currently has the capacity to meet its financial commitments; however, it faces major ongoing uncertainties that could lead to the obligor’s inadequate capacity to meet its financial commitments.

C: A short-term obligation rated ‘C’ is currently vulnerable to nonpayment and is dependent upon favorable business, financial, and economic conditions for the obligor to meet its financial commitments on the obligation.

D: A short-term obligation rated ‘D’ is in default or in breach of an imputed promise. For non-hybrid capital instruments, the ‘D’ rating category is used when payments on an obligation are not made on the date due, unless S&P believes that such payments will be made within any stated grace period. However, any stated grace period longer than five business days will be treated as five business days. The ‘D’ rating also will be used upon the filing of a bankruptcy petition or the taking of a similar action and where default on an obligation is a virtual certainty, for example due to automatic stay provisions. A rating on an obligation is lowered to ‘D’ if it is subject to a distressed debt restructuring.

Dual Ratings: Dual ratings may be assigned to debt issues that have a put option or demand feature. The first component of the rating addresses the likelihood of repayment of principal and interest as due, and the second component of the rating addresses only the demand feature. The first component of the rating can relate to either a short-term or long-term transaction and accordingly use either short-term or long-term rating symbols. The second component of the rating relates to the put option and is assigned a short-term rating symbol (for example, ‘AAA/A-1+‘ or ‘A-1+/ A-1’). With U.S. municipal short-term demand debt, the U.S. municipal short-term note rating symbols are used for the first component of the rating (for example, ‘SP-1+/A-1+‘).

Active Qualifiers

S&P uses the following qualifiers that limit the scope of a rating. The structure of the transaction can require the use of a qualifier such as a ‘p’ qualifier, which indicates the rating addresses the principal portion of the obligation only. A qualifier appears as a suffix and is part of the rating.

L: Ratings qualified with ‘L’ apply only to amounts invested up to federal deposit insurance limits.

p: This suffix is used for issues in which the credit factors, the terms, or both, that determine the likelihood of receipt of payment of principal are different from the credit factors, terms or both that determine the likelihood of receipt of interest on the obligation. The ‘p’ suffix indicates that the rating addresses the principal portion of the obligation only and that the interest is not rated.

prelim: Preliminary ratings, with the ‘prelim’ suffix, may be assigned to obligors or obligations, including financial programs, in the circumstances described below. Assignment of a final rating is conditional on the receipt by S&P of appropriate documentation. S&P reserves the right not to issue a final rating. Moreover, if a final rating is issued, it may differ from the preliminary rating.

■

Preliminary ratings may be assigned to obligations, most commonly structured and project finance issues, pending receipt of final documentation and legal opinions.

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Preliminary ratings may be assigned to obligations that will likely be issued upon the obligor’s emergence from bankruptcy or similar reorganization, based on late-stage reorganization plans, documentation and discussions with the obligor. Preliminary ratings may also be assigned to the obligors. These ratings consider the anticipated general credit quality of the reorganized or post-bankruptcy issuer as well as attributes of the anticipated obligation(s).

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Preliminary ratings may be assigned to entities that are being formed or that are in the process of being independently established when, in S&P’s opinion, documentation is close to final. Preliminary ratings may also be assigned to the obligations of these entities.

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Preliminary ratings may be assigned when a previously unrated entity is undergoing a well-formulated restructuring, recapitalization, significant financing or other transformative event, generally at the point that investor or lender commitments are invited. The preliminary rating may be assigned to the entity and to its proposed obligation(s). These preliminary ratings consider the anticipated general credit quality of the obligor, as well as attributes of the anticipated obligation(s), assuming successful completion of the transformative event. Should the transformative event not occur, S&P would likely withdraw these preliminary ratings.

■

A preliminary recovery rating may be assigned to an obligation that has a preliminary issue credit rating.

April 30, 2021 (as supplemented May 14, 2021) | PROSPECTUS A-4

PIMCO Flexible Municipal Income Fund

t: This symbol indicates termination structures that are designed to honor their contracts to full maturity or, should certain events occur, to terminate and cash settle all their contracts before their final maturity date.

cir: This symbol indicates a Counterparty Instrument Rating (CIR), which is a forward-looking opinion about the creditworthiness of an issuer in a securitization structure with respect to a specific financial obligation to a counterparty (including interest rate swaps, currency swaps, and liquidity facilities). The CIR is determined on an ultimate payment basis; these opinions do not take into account timeliness of payment.

Inactive Qualifiers (no longer applied or outstanding)

*:This symbol indicated that the rating was contingent upon S&P receipt of an executed copy of the escrow agreement or closing documentation confirming investments and cash flows. Discontinued use in August 1998.

c: This qualifier was used to provide additional information to investors that the bank may terminate its obligation to purchase tendered bonds if the long-term credit rating of the issuer was lowered to below an investment-grade level and/or the issuer’s bonds were deemed taxable. Discontinued use in January 2001.

G: The letter ‘G’ followed the rating symbol when a fund’s portfolio consisted primarily of direct U.S. government securities.

pi: This qualifier was used to indicate ratings that were based on an analysis of an issuer’s published financial information, as well as additional information in the public domain. Such ratings did not, however, reflect in-depth meetings with an issuer’s management and therefore, could have been based on less comprehensive information than ratings without a ‘pi’ suffix. Discontinued use as of December 2014 and as of August 2015 for Lloyd’s Syndicate Assessments.

pr: The letters ‘pr’ indicate that the rating was provisional. A provisional rating assumed the successful completion of a project financed by the debt being rated and indicates that payment of debt service requirements was largely or entirely dependent upon the successful, timely completion of the project. This rating, however, while addressing credit quality subsequent to completion of the project, made no comment on the likelihood of or the risk of default upon failure of such completion.

q: A ‘q’ subscript indicates that the rating is based solely on quantitative analysis of publicly available information. Discontinued use in April 2001.

r: The ‘r’ modifier was assigned to securities containing extraordinary risks, particularly market risks, that are not covered in the credit rating. The absence of an ‘r’ modifier should not be taken as an indication that an obligation would not exhibit extraordinary non-credit related risks. S&P discontinued the use of the ‘r’ modifier for most obligations in June 2000 and for the balance of obligations (mainly structured finance transactions) in November 2002.

Fitch Ratings

Long-Term Credit Ratings
Investment Grade

Rated entities in a number of sectors, including financial and non-financial corporations, sovereigns, insurance companies and certain sectors within public finance, are generally assigned Issuer Default Ratings (“IDRs”). IDRs are also assigned to certain entities or enterprises in global infrastructure, project finance, and public finance. IDRs opine on an entity’s relative vulnerability to default (including by way of a distressed debt exchange) on financial obligations. The threshold default risk addressed by the IDR is generally that of the financial obligations whose non-payment would best reflect the uncured failure of that entity. As such, IDRs also address relative vulnerability to bankruptcy, administrative receivership or similar concepts.

In aggregate, IDRs provide an ordinal ranking of issuers based on the agency’s view of their relative vulnerability to default, rather than a prediction of a specific percentage likelihood of default.

AAA: Highest credit quality. ‘AAA’ ratings denote the lowest expectation of default risk. They are assigned only in cases of exceptionally strong capacity for payment of financial commitments. This capacity is highly unlikely to be adversely affected by foreseeable events.

AA: Very high credit quality. ‘AA’ ratings denote expectations of very low default risk. They indicate very strong capacity for payment of financial commitments. This capacity is not significantly vulnerable to foreseeable events.

A: High credit quality. ‘A’ ratings denote expectations of low default risk. The capacity for payment of financial commitments is considered strong. This capacity may, nevertheless, be more vulnerable to adverse business or economic conditions than is the case for higher ratings.

BBB: Good credit quality. ‘BBB’ ratings indicate that expectations of default risk are currently low. The capacity for payment of financial commitments is considered adequate, but adverse business or economic conditions are more likely to impair this capacity.

Speculative Grade

BB: Speculative. ‘BB’ ratings indicate an elevated vulnerability to default risk, particularly in the event of adverse changes in business or economic conditions over time; however, business or financial flexibility exists that supports the servicing of financial commitments.

B: Highly speculative. ‘B’ ratings indicate that material default risk is present, but a limited margin of safety remains. Financial commitments are currently being met, however, capacity for continued payment is vulnerable to deterioration in the business and economic environment.

CCC: Substantial credit risk. Default is a real possibility.

CC: Very high levels of credit risk. Default of some kind appears probable.

C: Near default.

A-5 Prospectus | PIMCO Flexible Municipal Income Fund

Prospectus

A default or default-like process has begun, or the issuer is in standstill, or for a closed funding vehicle, payment capacity is irrevocably impaired. Conditions that are indicative of a ‘C’ category rating for an issuer include:

a. the issuer has entered into a grace or cure period following non-payment of a material financial obligation;

b. the issuer has entered into a temporary negotiated waiver or standstill agreement following a payment default on a material financial obligation;

c. the formal announcement by the issuer or their agent of a distressed debt exchange;

d. a closed financing vehicle where payment capacity is irrevocably impaired such that it is not expected to pay interest and/or principal in full during the life of the transaction, but where no payment default is imminent

RD: Restricted default. ‘RD’ ratings indicate an issuer that in Fitch Ratings’ opinion has experienced an uncured payment default or distressed debt exchange on a bond, loan or other material financial obligation but which has not entered into bankruptcy filings, administration, receivership, liquidation or other formal winding-up procedure, and which has not otherwise ceased operating. This would include:

i. the selective payment default on a specific class or currency of debt;

ii. the uncured expiry of any applicable grace period, cure period or default forbearance period following a payment default on a bank loan, capital markets security or other material financial obligation;

iii. the extension of multiple waivers or forbearance periods upon a payment default on one or more material financial obligations, either in series or in parallel; ordinary execution of a distressed debt exchange on one or more material financial obligations.

D: Default. ‘D’ ratings indicate an issuer that in Fitch Ratings’ opinion has entered into bankruptcy filings, administration, receivership, liquidation or other formal winding-up procedure or that has otherwise ceased business. Default ratings are not assigned prospectively to entities or their obligations; within this context, non-payment on an instrument that contains a deferral feature or grace period will generally not be considered a default until after the expiration of the deferral or grace period, unless a default is otherwise driven by bankruptcy or other similar circumstance, or by a distressed debt exchange.

In all cases, the assignment of a default rating reflects the agency’s opinion as to the most appropriate rating category consistent with the rest of its universe of ratings, and may differ from the definition of default under the terms of an issuer’s financial obligations or local commercial practice.

The modifiers “+” or “-” may be appended to a rating to denote relative status within major rating categories. For example, the rating category ‘AA’ has three notch-specific rating levels (’AA+‘; ’AA’; ‘AA-’; each a rating level). Such suffixes are not added to ‘AAA’ ratings and ratings below the ‘CCC’ category.

Recovery Ratings

Recovery Ratings are assigned to selected individual securities and obligations, most frequently for individual obligations of corporate finance issuers with IDRs in speculative grade categories.

Among the factors that affect recovery rates for securities are the collateral, the seniority relative to other obligations in the capital structure (where appropriate), and the expected value of the company or underlying collateral in distress.

The Recovery Rating scale is based on the expected relative recovery characteristics of an obligation upon the curing of a default, emergence from insolvency or following the liquidation or termination of the obligor or its associated collateral.

Recovery Ratings are an ordinal scale and do not attempt to precisely predict a given level of recovery. As a guideline in developing the rating assessments, the agency employs broad theoretical recovery bands in its ratings approach based on historical averages and analytical judgment, but actual recoveries for a given security may deviate materially from historical averages.

RR1: Outstanding recovery prospects given default. ‘RR1’ rated securities have characteristics consistent with securities historically recovering 91%-100% of current principal and related interest.

RR2: Superior recovery prospects given default. ‘RR2’ rated securities have characteristics consistent with securities historically recovering 71%-90% of current principal and related interest.

RR3: Good recovery prospects given default. ‘RR3’ rated securities have characteristics consistent with securities historically recovering 51%-70% of current principal and related interest.

RR4: Average recovery prospects given default. ‘RR4’ rated securities have characteristics consistent with securities historically recovering 31%-50% of current principal and related interest.

RR5: Below average recovery prospects given default. ‘RR5’ rated securities have characteristics consistent with securities historically recovering 11%-30% of current principal and related interest.

RR6: Poor recovery prospects given default. ‘RR6’ rated securities have characteristics consistent with securities historically recovering 0%-10% of current principal and related interest.

Short-Term Credit Ratings

A short-term issuer or obligation rating is based in all cases on the short-term vulnerability to default of the rated entity and relates to the capacity to meet financial obligations in accordance with the documentation governing the relevant obligation. Short-term deposit ratings may be adjusted for loss severity. Short-Term Ratings are assigned to obligations whose initial maturity is viewed as “short term” based on market convention. Typically, this means up to 13 months for corporate, sovereign, and structured obligations, and up to 36 months for obligations in U.S. public finance markets.

F1: Highest short-term credit quality. Indicates the strongest intrinsic capacity for timely payment of financial commitments; may have an added “+” to denote any exceptionally strong credit feature.

April 30, 2021 (as supplemented May 14, 2021) | PROSPECTUS A-6

PIMCO Flexible Municipal Income Fund

Appendix B

Financial Firm-Specific Sales Charge Waivers and Discounts

The availability of initial sales charge waivers and discounts may depend on the particular financial firm or type of account through which you purchase or hold Fund shares. For waivers or discounts not available through a particular financial firm, investors will have to purchase shares directly from the Fund (or the Distributor) or through another financial firm to receive such waivers or discounts.

The following descriptions of breakpoints and/or sales charge waivers and discounts for a particular financial firm and class(es) of shares set forth information provided by the financial firm that the firm has represented is current as of the date of this prospectus. These breakpoints, waivers or discounts, which may vary from those disclosed elsewhere in the prospectus, are subject to change. The Fund will update this Appendix periodically based on information provided by the applicable financial firm. Neither the Fund, the Investment Adviser nor PIMCO Investments LLC supervises the implementation of these breakpoints, waivers or discounts or verifies the firms’ administration of these breakpoints, waivers or discounts.

In all instances, it is an investor’s responsibility to notify the financial firm of any facts that may qualify the investor for sales charge waivers or discounts. Please contact your financial firm for more information regarding the sales charge waivers and discounts available to you and the firm’s related policies and procedures.

Rockefeller Financial LLC / Rockefeller & Co. LLC:

Effective December 1, 2020, shareholders purchasing Class A-2 Common Shares through Rockefeller Financial LLC or Rockefeller & Co. LLC will not pay any initial sales charge on the purchase and such Class A-2 Common Shares will not be subject to an early withdrawal charge if the shares are repurchased during the first 12 months after their purchase

UBS:

If you have an account with or otherwise purchase Fund shares through UBS Financial Services, Inc. (“UBS”), you may reduce or eliminate the sales charges applicable to purchases of Class A-2 Common Shares through utilization of the Combined Purchase Privilege, Right of Accumulation (Cumulative Quantity Discount), Letter of Intent or Reinstatement Privilege programs, as disclosed elsewhere in the prospectus. For purposes of such programs available to Class A-2 purchasers through UBS, these programs will apply to purchases of other open-end funds and closed-end interval funds that PIMCO sponsors currently or in the future that offer Class A (with respect to open-end funds) and Class A-2 (with respect to closed-end interval funds) (i.e., for purchases of Class A-2 Common Shares through UBS, the term “Eligible Funds” as used in this prospectus includes open-end funds sponsored by PIMCO that offer Class A shares). In addition, for purposes of these programs, for purchases of Class A-2 Common Shares through UBS, UBS may group related accounts by, first, combining the assets held in a household. In addition, accounts in one household can be combined with accounts in a second household if:

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The primary Social Security or Taxpayer Identification Number on an account in the first household matches the primary Social Security or Taxpayer Identification Number on an account in the second household.

■

Or, the primary Social Security or Taxpayer Identification Number on an account in one household matches a secondary Social Security or Taxpayer Identification Number in the second household, and each account in both households share the same nine-digit ZIP code.

In certain circumstances, additional criteria may be applied, and UBS reserves the right, in its sole discretion, to grant exceptions. Additional information about UBS’ policies related to these programs, including regarding the aggregation methods employed by UBS, is available at the UBS website, https://www.ubs.com/us/en/wealth-management/information/account-disclosures.html.

B-1 Prospectus | PIMCO Flexible Municipal Income Fund

		Ratios/Supplemental Data
			Ratios to Average Net Assets
Net Asset Value End of Year or Period(a)	Total Return(a)	Net Assets Applicable to Common Shareholders End of Year or Period (000s)	Expenses(d)	Expenses Excluding Waivers(d)	Expenses Excluding Interest Expense	Expenses Excluding Interest Expense and Waivers	Net Investment Income (Loss)	Portfolio Turnover Rate

$11.45	10.00%	$317,646	0.88%	1.19%	0.47%	0.78%	2.35%	88%
10.74	10.74	148,737	0.72*	1.87*	0.11*	1.26*	2.73*	96

$11.45	13.28%	$56,540	1.38%*	1.69%*	0.97%*	1.28%*	2.59%*	88%

$11.45	5.25%	$11.00	1.38%*	1.69%*	0.97%*	1.28%*	2.66%*	88%

$11.45	9.18%	$155,532	1.63%	1.94%	1.22%	1.53%	2.09%	88%
10.74	0.98	44,330	1.47*	2.62*	0.86*	2.01*	2.12*	96

	RVMTP & VMTP
Selected Per Share Data for the Year or Period Ended^:	Total Amount Outstanding	Asset Coverage per Preferred Share(1)	Involuntary Liquidating Preference per Preferred Share(2)	Average Market Value per Preferred Share(3)
PIMCO Flexible Municipal Income Fund
12/31/2020	$150,000,000	$453,120	$100,000	N/A
03/15/2019 - 12/31/2019	50,000,000	486,130	$100,000	N/A

	Page
Prospectus Summary	1
Summary of Fund Expenses	17
Financial Highlights	19
The Fund	22
Use of Proceeds	22
The Fund’s Investment Objectives and Strategies	22
Use of Leverage	33
Principal Risks of the Fund	35
How the Fund Manages Risk	48
Management of the Fund	50
Plan of Distribution	54
Periodic Repurchase Offers	63
Net Asset Value	65
Distributions	67
Dividend Reinvestment Plan	68
Description of Capital Structure and Shares	68
Anti-Takeover and Other Provisions in the Declaration of Trust	74
Tax Matters	74
Custodian and Transfer Agent	75
Independent Registered Public Accounting Firm	75
Legal Matters	76
Appendix A - Description of Securities Ratings	A-1
Appendix B - Financial Firm-Specific Sales Charge Waivers and Discounts	B-1