Significant Accounting Policies and Recent Accounting Updates	6 Months Ended
Mar. 31, 2023
Accounting Policies [Abstract]
Significant Accounting Policies and Recent Accounting Updates	Note 2. Significant Accounting Policies and Recent Accounting Updates Basis of presentation: The Company is an investment company as defined in the accounting and reporting guidance under Accounting Standards Codification (“ASC”) Topic 946 — Financial Services — Investment Companies (“ASC Topic 946”). The accompanying unaudited interim consolidated financial statements of the Company and related financial information have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) as established by the Financial Accounting Standards Board (“FASB”) for the interim financial information and pursuant to the requirements for reporting on Form 10-Q and Articles 6, 10 and 12 of Regulation S-X. Accordingly, they do not include all of the information and notes required by GAAP for annual financial statements. In the opinion of management, the consolidated financial statements reflect all adjustments and reclassifications consisting solely of normal accruals that are necessary for the fair presentation of financial results as of and for the periods presented. All intercompany balances and transactions have been eliminated. Certain prior period amounts have been reclassified to conform to the current period presentation. The unaudited interim consolidated financial statements and notes thereto should be read in conjunction with the financial statements and notes thereto in the Company’s Form 10-K for the year ended September 30, 2022, as filed with the U.S. Securities and Exchange Commission (the “SEC”). Fair value of financial instruments: The Company applies fair value to all of its financial instruments in accordance with ASC Topic 820 — Fair Value Measurement (“ASC Topic 820”). ASC Topic 820 defines fair value, establishes a framework used to measure fair value and requires disclosures for fair value measurements. In accordance with ASC Topic 820, the Company has categorized its financial instruments carried at fair value, based on the priority of the valuation technique, into a three-level fair value hierarchy. Fair value is a market-based measure considered from the perspective of the market participant who holds the financial instrument rather than an entity-specific measure. Therefore, when market assumptions are not readily available, the Company’s own assumptions are set to reflect those that management believes market participants would use in pricing the financial instrument at the measurement date. The availability of observable inputs can vary depending on the financial instrument and is affected by a wide variety of factors, including, for example, the type of product, whether the product is new, whether the product is traded on an active exchange or in the secondary market and the current market conditions. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for financial instruments classified as Level 3. Any changes to the valuation methodology are reviewed by management and the Company’s board of directors (the “Board”) to confirm that the changes are appropriate. As markets change, new products develop and the pricing for products becomes more or less transparent, the Company will continue to refine its valuation methodologies. See further description of fair value methodology in Note 6. Fair Value Measurements. Use of estimates: The preparation of the unaudited consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Consolidation: As provided under Regulation S-X and ASC Topic 946, the Company will generally not consolidate its investment in a company other than an investment company subsidiary or a controlled operating company whose business consists of providing services to the Company. Accordingly, the Company consolidated the results of the Company’s wholly-owned subsidiaries Golub Capital BDC CLO III Depositor LLC (“2018 CLO Depositor”); Golub Capital BDC CLO III LLC (“2018 Issuer”); Golub Capital BDC Holdings, LLC (“BDC Holdings”); GCIC Holdings LLC (“GCIC Holdings”); GCIC CLO II Depositor LLC (“GCIC 2018 CLO Depositor”); GCIC CLO II LLC (“GCIC 2018 Issuer”); GCIC Funding LLC (“GCIC Funding”); GBDC Holdings Coinvest, Inc.; GBDC Holdings ED Coinvest, Inc.; GCIC North Haven Stack Buyer Coinvest, Inc.; GCIC Quick Quack Coinvest LLC; GBDC Quick Quack Coinvest LLC; prior to March 23, 2022, the date of each of the following entity’s dissolution, Golub Capital BDC CLO 4 Depositor LLC (“2020 CLO Depositor”), GC SBIC V, L.P. (“SBIC V”), Senior Loan Fund LLC and Senior Loan Fund II LLC; prior to its dissolution on September 16, 2022, Golub Capital BDC Funding II LLC (“Funding II”); and prior to September 27, 2022, the date of each of the following entity’s dissolution, GCIC Funding II LLC (“GCIC Funding II”), Golub Capital BDC Funding LLC (“Funding”) and GC SBIC VI, L.P. (“SBIC VI”). Assets related to transactions that do not meet ASC Topic 860 requirements for accounting sale treatment are reflected in the Company’s Consolidated Statements of Financial Condition as investments. Those assets are owned by special purpose entities, including BDC Holdings, 2018 Issuer, Funding II, GCIC Holdings and the GCIC 2018 Issuer that are consolidated in the Company’s consolidated financial statements. The creditors of the special purpose entities have received security interests in such assets and such assets are not intended to be available to the creditors of GBDC (or any affiliate of GBDC). Cash and cash equivalents and foreign currencies: Cash, cash equivalents and foreign currencies are highly liquid investments with an original maturity of three months or less at the date of acquisition. The Company deposits its cash in financial institutions and, at times, such balances exceed the Federal Deposit Insurance Corporation insurance limits. Restricted cash and cash equivalents and restricted foreign currencies: Restricted cash and cash equivalents and restricted foreign currencies include amounts that are collected and are held by trustees who have been appointed as custodians of the assets securing certain of the Company’s financing transactions. Restricted cash and cash equivalents and restricted foreign currencies are held by the trustees for payment of interest expense and principal on the outstanding borrowings or reinvestment into new assets. Foreign currency translation: The Company’s books and records are maintained in U.S. dollars. Any foreign currency amounts are translated into U.S. dollars. Non-U.S. dollar transactions during the year are valued at the prevailing spot rates on the applicable transaction date and the related assets and liabilities are revalued at the prevailing spot rates as of period-end. Net assets and fair values are presented based on the applicable foreign exchange rates and fluctuations arising from the translation of assets and liabilities are included with the net change in unrealized appreciation (depreciation) on translation of assets and liabilities in foreign currencies on the Consolidated Statements of Operations. Foreign security and currency transactions involve certain considerations and risks not typically associated with investing in U.S. companies. These risks include, but are not limited to, currency fluctuations and revaluations and future adverse political, social and economic developments, which could cause investments in foreign markets to be less liquid and prices more volatile than those of comparable U.S. companies or U.S. government securities. Forward currency contracts: A forward currency contract is an obligation between two parties to purchase or sell a specific currency for an agreed-upon price at a future date. The Company utilized forward currency contracts to economically hedge the currency exposure associated with certain foreign-denominated investments. The use of forward currency contracts does not eliminate fluctuations in the price of the underlying securities the Company owns or intends to acquire but establishes a rate of exchange in advance. Fluctuations in the value of these contracts are measured by the difference in the exchange rates on the contract date and reporting date and are recorded as unrealized appreciation (depreciation) until the contracts are closed. When the contracts are closed, realized gains (losses) are recorded. Realized gains (losses) and unrealized appreciation (depreciation) on the contracts are included in the Consolidated Statements of Operations. Unrealized appreciation (depreciation) on forward currency contracts is recorded on the Consolidated Statements of Financial Condition by counterparty on a net basis, not taking into account collateral posted which is recorded separately, if applicable. The primary risks associated with forward currency contracts include failure of the counterparty to meet the terms of the contract and the value of the foreign currency changing unfavorably. These risks can exceed the amounts reflected in the Consolidated Statements of Financial Condition. Refer to Note 5 for more information regarding the forward currency contracts. Revenue recognition: Investments and related investment income: Interest income is accrued based upon the outstanding principal amount and contractual interest terms of debt investments. Loan origination fees, original issue discount and market discount or premium are capitalized, and the Company accretes or amortizes such amounts over the life of the loan as interest income. For the three and six months ended March 31, 2023, interest income included $4,663 and $10,691, respectively, of accretion of discounts. For the three and six months ended March 31, 2022, interest income included $4,048 and $11,783, respectively, of accretion of discounts. For the three and six months ended March 31, 2023, the Company received loan origination fees of $4,762 and $11,386, respectively. For the three and six months ended March 31, 2022, the Company received loan origination fees of $4,804 and $16,016, respectively. For investments with contractual payment-in-kind (“PIK”) interest, which represents contractual interest accrued and added to the principal balance that generally becomes due at maturity, the Company will not accrue PIK interest if the portfolio company valuation indicates that the PIK interest is not collectible. For the three and six months ended March 31, 2023, interest income included $9,164 and $17,683, respectively, of PIK interest and the Company capitalized PIK interest of $9,478 and $17,255, respectively, into the principal balance of certain debt investments. For the three and six months ended March 31, 2022, interest income included $4,613 and $8,943, respectively, of PIK interest and the Company capitalized PIK interest of $5,124 and $8,597, respectively, into the principal balance of certain debt investments. In addition, the Company generates revenue in the form of amendment, structuring or due diligence fees, fees for providing managerial assistance, consulting fees, administrative agent fees, and prepayment premiums on loans. The Company records these fees as fee income when earned. All other income is recorded into income when earned. For the three months ended March 31, 2023, there was no fee income from non-recurring prepayments premiums. For the six months ended March 31, 2023, fee income included $79 from non-recurring prepayment premiums. For the three and six months ended March 31, 2022, fee income included $103 and $795, respectively, of non-recurring prepayment premiums. For the three and six months ended March 31, 2023, the Company received interest and fee income in cash, which excludes capitalized loan origination fees, in the amounts of $127,648 and $241,181, respectively. For the three and six months ended March 31, 2022, the Company received interest and fee income in cash, which excludes capitalized loan origination fees, in the amounts of $82,033 and $162,023, respectively. Dividend income on equity securities is recorded as dividend income on an accrual basis to the extent that such amounts are payable by the portfolio company and are expected to be collected. The Company has certain preferred equity securities in the portfolio that contain a PIK dividend provision that are accrued and recorded as income at the contractual rates, if deemed collectible. The accrued PIK and non-cash dividends are capitalized to the cost basis of the preferred equity security and are generally collected when redeemed by the issuer. For the three and six months ended March 31, 2023, dividend income included and the Company capitalized PIK and non-cash dividends of $3,595 and $7,044, respectively, into the cost basis of certain preferred equity investments. For the three and six months ended March 31, 2022, the Company had no capitalized PIK and non-cash dividends. For the three and six months ended March 31, 2023 and 2022, the Company received no cash payments of accrued and capitalized preferred dividends in cash. Dividend income on common equity securities is recorded on the record date for private portfolio companies or on the ex-dividend date for publicly traded portfolio companies. Each distribution received from limited liability company (“LLC”) and limited partnership (“LP”) investments is evaluated to determine if the distribution should be recorded as dividend income or a return of capital. Generally, the Company will not record distributions from equity investments in LLCs and LPs as dividend income unless there are sufficient accumulated tax-basis earnings and profits in the LLC or LP prior to the distribution. Distributions that are classified as a return of capital are recorded as a reduction in the amortized cost basis of the investment. For the three and six months ended March 31, 2023, the Company recorded dividend income received in cash of $311 and $995, respectively, and return of capital cash distributions of $83 and $83, respectively. For the three and six months ended March 31, 2022, the Company recorded dividend income received in cash of $3 and $320, respectively, and return of capital cash distributions of $596 and $726, respectively. Investment transactions are accounted for on a trade-date basis. Realized gains or losses on investments are measured by the difference between the net proceeds from the disposition and the amortized cost basis of investment, without regard to unrealized gains or losses previously recognized. The Company reports current period changes in fair value of investments that are measured at fair value as a component of the net change in unrealized appreciation (depreciation) on investment transactions in the Consolidated Statements of Operations. Non-accrual loans: A loan can be left on accrual status during the period the Company is pursuing repayment of the loan. Management reviews all loans that become 90 days or more past due on principal and interest, or when there is reasonable doubt that principal or interest will be collected, for possible placement on non-accrual status. When a loan is placed on non-accrual status, unpaid interest credited to income is reversed. Additionally, any original issue discount and market discount are no longer accreted to interest income as of the date the loan is placed on non-accrual status. Interest payments received on non-accrual loans are recognized as income or applied to principal depending upon management’s judgment. Non-accrual loans are restored to accrual status when past due principal and interest is paid and, in management’s judgment, payments are likely to remain current. The total fair value of non-accrual loans was $88,581 and $65,125 as of March 31, 2023 and September 30, 2022, respectively. Purchase accounting: On September 16, 2019, the Company completed its acquisition of Golub Capital Investment Corporation (“GCIC”), a Maryland corporation, pursuant to that certain Agreement and Plan of Merger (as amended, the “Merger Agreement”), dated as of November 27, 2018, by and among the Company, GCIC, Fifth Ave Subsidiary Inc., a Maryland corporation and wholly owned subsidiary of the Company (“Merger Sub”), the Investment Adviser, and, for certain limited purposes, the Administrator. Pursuant to the Merger Agreement, Merger Sub was first merged with and into GCIC, with GCIC as the surviving company (the “Initial Merger”), and, immediately following the Initial Merger, GCIC was then merged with and into the Company, with the Company as the surviving company (the Initial Merger and the subsequent merger, collectively, the “Merger”). The Merger was accounted for under the asset acquisition method of accounting in accordance with ASC 805 — Business Combinations — Related Issues (“ASC Topic 805”), also referred to as “purchase accounting.” Under asset acquisition accounting, acquiring assets in groups not only requires ascertaining the cost of the asset (or net assets), but also allocating that cost to the individual assets (or individual assets and liabilities) that make up the group. Per ASC Topic 805, assets are recognized based on their cost to the acquiring entity, which generally includes transaction costs of the asset acquisition, and no gain or loss is recognized unless the fair value of non-cash assets given as consideration differs from the assets carrying amounts on the acquiring entity’s books. The cost of the group of assets acquired in an asset acquisition is allocated to the individual assets acquired or liabilities assumed based on the relative fair values of net identifiable assets acquired other than “non-qualifying” assets (for example cash) and does not give rise to goodwill. To the extent that the consideration paid to GCIC’s stockholders exceeded the relative fair values of the net identifiable assets of GCIC acquired other than “non-qualifying” assets, any such premium paid by the Company was further allocated to the cost of the GCIC assets acquired by the Company pro-rata to their relative fair value, other than “non-qualifying” assets. As GCIC did not have any “qualifying” assets at the time of acquisition, the premium was allocated to “non-qualifying” assets, which are GCIC’s investments in loans and equity securities, including its investment in GCIC SLF. Immediately following the acquisition of GCIC, the Company recorded its assets at their respective fair values and, as a result, the purchase premium allocated to the cost basis of the GCIC assets acquired was immediately recognized as unrealized depreciation on the Company's Consolidated Statement of Operations. The purchase premium allocated to investments in loan securities will amortize over the life of the loans through interest income, with a corresponding reversal of the unrealized depreciation on the loans acquired from GCIC through their ultimate disposition. Amortization expense of purchase premium for the three and six months ended March 31, 2023 was $1,652 and $3,787, respectively. Amortization expense of purchase premium for the three and six months ended March 31, 2022 was $2,940 and $10,035, respectively. The purchase premium allocated to investments in equity securities will not amortize over the life of the equity securities through interest income and, assuming no subsequent change to the fair value of the equity securities acquired from GCIC and disposition of such equity securities at fair value, the Company will recognize a realized loss with a corresponding reversal of the unrealized depreciation upon disposition of the equity securities acquired from GCIC. Income taxes: The Company has elected to be treated as a RIC under Subchapter M of the Code and operates in a manner so as to qualify for the tax treatment applicable to RICs. In order to qualify and be subject to tax as a RIC, among other things, the Company is required to meet certain source of income and asset diversification requirements and timely distribute dividends for U.S. federal income tax purposes to its stockholders of an amount generally at least equal to 90% of investment company taxable income, as defined by the Code and determined without regard to any deduction for dividends paid, for each tax year. The Company has made, and intends to continue to make, the requisite distributions to its stockholders, which will generally relieve the Company from U.S. federal income taxes with respect to all income distributed to its stockholders. Depending on the level of taxable income earned in a tax year, the Company can determine to retain taxable income in excess of current year dividend distributions and distribute such taxable income in the next tax year. The Company may then be required to incur a 4% excise tax on such income. To the extent that the Company determines that its estimated current year annual taxable income, determined on a calendar year basis, could exceed estimated current calendar year dividend distributions, the Company accrues excise tax, if any, on estimated excess taxable income as taxable income is earned. For the three and six months ended March 31, 2023, $232 and $2,432, respectively, was recorded for U.S. federal excise tax. For the three and six months ended March 31, 2022, the Company did not record any U.S. federal excise tax. The Company accounts for income taxes in conformity with ASC Topic 740 — Income Taxes (“ASC Topic 740”). ASC Topic 740 provides guidelines for how uncertain tax positions should be recognized, measured, presented and disclosed in financial statements. ASC Topic 740 requires the evaluation of tax positions taken in the course of preparing the Company’s tax returns to determine whether the tax positions are “more-likely-than-not” to be sustained by the applicable tax authority. Tax benefits of positions not deemed to meet the more-likely-than-not threshold would be recorded as a tax expense or tax benefit in the current year. It is the Company’s policy to recognize accrued interest and penalties related to uncertain tax benefits in income tax expense. There were no material unrecognized tax benefits or unrecognized tax liabilities related to uncertain income tax positions through March 31, 2023. The Company's tax returns for the 2019 through 2021 tax years remain subject to examination by U.S. federal and most state tax authorities. Certain of the Company's consolidated subsidiaries are subject to U.S. federal and state corporate-level income taxes. Income tax expense, if any, is included under the income category for which it applies in the Consolidated Statements of Operations. Dividends and distributions: Dividends and distributions to common stockholders are recorded on the ex-dividend date. The amount to be paid out as a dividend or distribution is determined by the Board each quarter and is generally based upon the earnings estimated by management. Net realized capital gains, if any, are distributed at least annually, although the Company can retain such capital gains for investment in its discretion. The Company has adopted a dividend reinvestment plan (“DRIP”) that provides for reinvestment of any distributions the Company declares in cash on behalf of its stockholders, unless a stockholder elects to receive cash. As a result, if the Board authorizes and the Company declares a cash distribution, then stockholders who participate in the DRIP will have their cash distribution reinvested in additional shares of the Company’s common stock, rather than receiving the cash distribution. The Company expects to use newly issued shares under the guidelines of the DRIP if the Company’s shares are trading at a premium to net asset value. The Company can purchase shares in the open market in connection with the obligations under the plan, and in particular, if the Company’s shares are trading at a significant discount to net asset value (“NAV”) and the Company is otherwise permitted under applicable law to purchase such shares, the Company intends to purchase shares in the open market in connection with any obligations under the DRIP. In the event the market price per share of the Company’s common stock on the date of a distribution exceeds the most recently computed NAV per share of the common stock, the Company will issue shares of common stock to participants in the DRIP at the greater of the most recently computed NAV per share of common stock or 95% of the current market price per share of common stock (or such lesser discount to the current market price per share that still exceeds the most recently computed NAV per share of common stock). Share repurchase plan: The Company has a share repurchase program (the “Program”) which allows the Company to repurchase the Company’s outstanding common stock on the open market at prices below the Company’s NAV as reported in its most recently published consolidated financial statements. The Board most recently reapproved the Program in August 2022 and the Program is implemented at the discretion of management. Shares can be purchased from time to time at prevailing market prices, through open market transactions, including block transactions. The Program permits repurchases up to $150 million of the Company's common stock. Refer to Note 12 for more information on the share repurchases under the Program. Equity Distribution Agreement: On May 28, 2021, the Company entered into an equity distribution agreement (the “Equity Distribution Agreement”), by and among the Company, the Investment Adviser, Golub Capital LLC and SMBC Nikko Securities America, Inc. (the “Placement Agent”), in connection with the sale by the Company of shares of its common stock, having an aggregate offering price of up to $250,000, in an “at the market offering,” in amounts and at times to be determined by the Company. Actual sales, if any, will depend on a variety of factors to be determined by the Company from time to time, including, among others, market conditions and the market price of the Company’s common stock. The Equity Distribution Agreement provides that the Company may offer and sell shares from time to time through the Placement Agent, or to it. Sales of the shares, if any, may be made in negotiated transactions or transactions that are deemed to be “at the market,” as defined in Rule 415 under the Securities Act of 1933, as amended, including sales made directly on The Nasdaq Global Select Market or any similar securities exchange or sales made to or through a market maker other than on a securities exchange, at prices related to the prevailing market prices or at negotiated prices. Pursuant to the terms of the Equity Distribution Agreement, the Placement Agent will receive a commission from the Company of up to 1.25% of the gross sales price of any shares sold through the Placement Agent under the Equity Distribution Agreement. Offering costs for the Equity Distribution Agreement are charged against the proceeds from equity offerings when proceeds are received. During the three and six months ended March 31, 2023 and 2022, the Company did not issue any shares of common stock under the Equity Distribution Agreement. Deferred debt issuance costs: Deferred debt issuance costs represent fees and other direct incremental costs incurred in connection with the Company’s borrowings. As of March 31, 2023 and September 30, 2022, the Company had deferred debt issuance costs of $19,154 and $17,211, respectively. These amounts are amortized and included in interest expense in the Consolidated Statements of Operations over the estimated average life of the borrowings. Amortization expense for deferred debt issuance costs for the three and six months ended March 31, 2023 was $1,677 and $3,425, respectively. Amortization expense for deferred debt issuance costs for the three and six months ended March 31, 2022 was $1,776 and $3,443, respectively.Deferred offering costs: Deferred offering costs consist of fees paid in relation to legal, accounting, regulatory and printing work completed in preparation of equity offerings. Deferred offering costs are charged against the proceeds from equity offerings when received. These amounts are included in other assets on the Consolidated Statements of Financial Condition.

The accompanying unaudited interim consolidated financial statements of the Company and related financial information have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) as established by the Financial Accounting Standards Board (“FASB”) for the interim financial information and pursuant to the requirements for reporting on Form 10-Q and Articles 6, 10 and 12 of Regulation S-X. Accordingly, they do not include all of the information and notes required by GAAP for annual financial statements. In the opinion of management, the consolidated financial statements reflect all adjustments and reclassifications consisting solely of normal accruals that are necessary for the fair presentation of financial results as of and for the periods presented. All intercompany balances and transactions have been eliminated. Certain prior period amounts have been reclassified to conform to the current period presentation. The unaudited interim consolidated financial statements and notes thereto should be read in conjunction with the financial statements and notes thereto in the Company’s Form 10-K for the year ended September 30, 2022, as filed with the U.S. Securities and Exchange Commission (the “SEC”).

Fair value of financial instruments: The Company applies fair value to all of its financial instruments in accordance with ASC Topic 820 — Fair Value Measurement (“ASC Topic 820”). ASC Topic 820 defines fair value, establishes a framework used to measure fair value and requires disclosures for fair value measurements. In accordance with ASC Topic 820, the Company has categorized its financial instruments carried at fair value, based on the priority of the valuation technique, into a three-level fair value hierarchy. Fair value is a market-based measure considered from the perspective of the market participant who holds the financial instrument rather than an entity-specific measure. Therefore, when market assumptions are not readily available, the Company’s own assumptions are set to reflect those that management believes market participants would use in pricing the financial instrument at the measurement date.

The availability of observable inputs can vary depending on the financial instrument and is affected by a wide variety of factors, including, for example, the type of product, whether the product is new, whether the product is traded on an active exchange or in the secondary market and the current market conditions. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for financial instruments classified as Level 3.

Use of estimates: The preparation of the unaudited consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

the results of the Company’s wholly-owned subsidiaries Golub Capital BDC CLO III Depositor LLC (“2018 CLO Depositor”); Golub Capital BDC CLO III LLC (“2018 Issuer”); Golub Capital BDC Holdings, LLC (“BDC Holdings”); GCIC Holdings LLC (“GCIC Holdings”); GCIC CLO II Depositor LLC (“GCIC 2018 CLO Depositor”); GCIC CLO II LLC (“GCIC 2018 Issuer”); GCIC Funding LLC (“GCIC Funding”); GBDC Holdings Coinvest, Inc.; GBDC Holdings ED Coinvest, Inc.; GCIC North Haven Stack Buyer Coinvest, Inc.; GCIC Quick Quack Coinvest LLC; GBDC Quick Quack Coinvest LLC; prior to March 23, 2022, the date of each of the following entity’s dissolution, Golub Capital BDC CLO 4 Depositor LLC (“2020 CLO Depositor”), GC SBIC V, L.P. (“SBIC V”), Senior Loan Fund LLC and Senior Loan Fund II LLC; prior to its dissolution on September 16, 2022, Golub Capital BDC Funding II LLC (“Funding II”); and prior to September 27, 2022, the date of each of the following entity’s dissolution, GCIC Funding II LLC (“GCIC Funding II”), Golub Capital BDC Funding LLC (“Funding”) and GC SBIC VI, L.P. (“SBIC VI”).

Assets related to transactions that do not meet ASC Topic 860 requirements for accounting sale treatment are reflected in the Company’s Consolidated Statements of Financial Condition as investments. Those assets are owned by special purpose entities, including BDC Holdings, 2018 Issuer, Funding II, GCIC Holdings and the GCIC 2018 Issuer that are consolidated in the Company’s consolidated financial statements. The creditors of the special purpose entities have received security interests in such assets and such assets are not intended to be available to the creditors of GBDC (or any affiliate of GBDC).

Restricted cash and cash equivalents and restricted foreign currencies: Restricted cash and cash equivalents and restricted foreign currencies include amounts that are collected and are held by trustees who have been appointed as custodians of the assets securing certain of the Company’s financing transactions. Restricted cash and cash equivalents and restricted foreign currencies are held by the trustees for payment of interest expense and principal on the outstanding borrowings or reinvestment into new assets.

Foreign security and currency transactions involve certain considerations and risks not typically associated with investing in U.S. companies. These risks include, but are not limited to, currency fluctuations and revaluations and future adverse political, social and economic developments, which could cause investments in foreign markets to be less liquid and prices more volatile than those of comparable U.S. companies or U.S. government securities.

Forward currency contracts: A forward currency contract is an obligation between two parties to purchase or sell a specific currency for an agreed-upon price at a future date. The Company utilized forward currency contracts to economically hedge the currency exposure associated with certain foreign-denominated investments. The use of forward currency contracts does not eliminate fluctuations in the price of the underlying securities the Company owns or intends to acquire but establishes a rate of exchange in advance. Fluctuations in the value of these contracts are measured by the difference in the exchange rates on the contract date and reporting date and are recorded as unrealized appreciation (depreciation) until the contracts are closed. When the contracts are closed, realized gains (losses) are recorded. Realized gains (losses) and unrealized appreciation (depreciation) on the contracts are included in the Consolidated Statements of Operations. Unrealized appreciation (depreciation) on forward currency contracts is recorded on the Consolidated Statements of Financial Condition by counterparty on a net basis, not taking into account collateral posted which is recorded separately, if applicable.

Loan origination fees, original issue discount and market discount or premium are capitalized, and the Company accretes or amortizes such amounts over the life of the loan as interest income. For the three and six months ended March 31, 2023, interest income included $4,663 and $10,691, respectively, of accretion of discounts. For the three and six months ended March 31, 2022, interest income included $4,048 and $11,783, respectively, of accretion of discounts. For the three and six months ended March 31, 2023, the Company received loan origination fees of $4,762 and $11,386, respectively. For the three and six months ended March 31, 2022, the Company received loan origination fees of $4,804 and $16,016, respectively.

For investments with contractual payment-in-kind (“PIK”) interest, which represents contractual interest accrued and added to the principal balance that generally becomes due at maturity, the Company will not accrue PIK interest if the portfolio company valuation indicates that the PIK interest is not collectible. For the three and six months ended March 31, 2023, interest income included $9,164 and $17,683, respectively, of PIK interest and the Company capitalized PIK interest of $9,478 and $17,255, respectively, into the principal balance of certain debt investments. For the three and six months ended March 31, 2022, interest income included $4,613 and $8,943, respectively, of PIK interest and the Company capitalized PIK interest of $5,124 and $8,597, respectively, into the principal balance of certain debt investments.

In addition, the Company generates revenue in the form of amendment, structuring or due diligence fees, fees for providing managerial assistance, consulting fees, administrative agent fees, and prepayment premiums on loans. The Company records these fees as fee income when earned. All other income is recorded into income when earned. For the three months ended March 31, 2023, there was no fee income from non-recurring prepayments premiums. For the six months ended March 31, 2023, fee income included $79 from non-recurring prepayment premiums. For the three and six months ended March 31, 2022, fee income included $103 and $795, respectively, of non-recurring prepayment premiums.

Dividend income on equity securities is recorded as dividend income on an accrual basis to the extent that such amounts are payable by the portfolio company and are expected to be collected. The Company has certain preferred equity securities in the portfolio that contain a PIK dividend provision that are accrued and recorded as income at the contractual rates, if deemed collectible. The accrued PIK and non-cash dividends are capitalized to the cost basis of the preferred equity security and are generally collected when redeemed by the issuer. For the three and six months ended March 31, 2023, dividend income included and the Company capitalized PIK and non-cash dividends of $3,595 and $7,044, respectively, into the cost basis of certain preferred equity investments. For the three and six months ended March 31, 2022, the Company had no capitalized PIK and non-cash dividends. For the three and six months ended March 31, 2023 and 2022, the Company received no cash payments of accrued and capitalized preferred dividends in cash.

Dividend income on common equity securities is recorded on the record date for private portfolio companies or on the ex-dividend date for publicly traded portfolio companies. Each distribution received from limited liability company (“LLC”) and limited partnership (“LP”) investments is evaluated to determine if the distribution should be recorded as dividend income or a return of capital. Generally, the Company will not record distributions from equity investments in LLCs and LPs as dividend income unless there are sufficient accumulated tax-basis earnings and profits in the LLC or LP prior to the distribution. Distributions that are classified as a return of capital are recorded as a reduction in the amortized cost basis of the investment.

Investment transactions are accounted for on a trade-date basis. Realized gains or losses on investments are measured by the difference between the net proceeds from the disposition and the amortized cost basis of investment, without regard to unrealized gains or losses previously recognized. The Company reports current period changes in fair value of investments that are measured at fair value as a component of the net change in unrealized appreciation (depreciation) on investment transactions in the Consolidated Statements of Operations.

Non-accrual loans: A loan can be left on accrual status during the period the Company is pursuing repayment of the loan. Management reviews all loans that become 90 days or more past due on principal and interest, or when there is reasonable doubt that principal or interest will be collected, for possible placement on non-accrual status. When a loan is placed on non-accrual status, unpaid interest credited to income is reversed. Additionally, any original issue discount and market discount are no longer accreted to interest income as of the date the loan is placed on non-accrual status. Interest payments received on non-accrual loans are recognized as income or applied to principal depending upon management’s judgment. Non-accrual loans are restored to accrual status when past due principal and interest is paid and, in management’s judgment, payments are likely to remain current. The total fair value of non-accrual loans was $88,581 and $65,125 as of March 31, 2023 and September 30, 2022, respectively.

Purchase accounting: On September 16, 2019, the Company completed its acquisition of Golub Capital Investment Corporation (“GCIC”), a Maryland corporation, pursuant to that certain Agreement and Plan of Merger (as amended, the “Merger Agreement”), dated as of November 27, 2018, by and among the Company, GCIC, Fifth Ave Subsidiary Inc., a Maryland corporation and wholly owned subsidiary of the Company (“Merger Sub”), the Investment Adviser, and, for certain limited purposes, the Administrator. Pursuant to the Merger Agreement, Merger Sub was first merged with and into GCIC, with GCIC as the surviving company (the “Initial Merger”), and, immediately following the Initial Merger, GCIC was then merged with and into the Company, with the Company as the surviving company (the Initial Merger and the subsequent merger, collectively, the “Merger”). The Merger was accounted for under the asset acquisition method of accounting in accordance with ASC 805 — Business Combinations — Related Issues (“ASC Topic 805”), also referred to as “purchase accounting.” Under asset acquisition accounting, acquiring assets in groups not only requires ascertaining the cost of the asset (or net assets), but also allocating that cost to the individual assets (or individual assets and liabilities) that make up the group. Per ASC Topic 805, assets are recognized based on their cost to the acquiring entity, which generally includes

The cost of the group of assets acquired in an asset acquisition is allocated to the individual assets acquired or liabilities assumed based on the relative fair values of net identifiable assets acquired other than “non-qualifying” assets (for example cash) and does not give rise to goodwill. To the extent that the consideration paid to GCIC’s stockholders exceeded the relative fair values of the net identifiable assets of GCIC acquired other than “non-qualifying” assets, any such premium paid by the Company was further allocated to the cost of the GCIC assets acquired by the Company pro-rata to their relative fair value, other than “non-qualifying” assets. As GCIC did not have any “qualifying” assets at the time of acquisition, the premium was allocated to “non-qualifying” assets, which are GCIC’s investments in loans and equity securities, including its investment in GCIC SLF. Immediately following the acquisition of GCIC, the Company recorded its assets at their respective fair values and, as a result, the purchase premium allocated to the cost basis of the GCIC assets acquired was immediately recognized as unrealized depreciation on the Company's Consolidated Statement of Operations. The purchase premium allocated to investments in loan securities will amortize over the life of the loans through interest income, with a corresponding reversal of the unrealized depreciation on the loans acquired from GCIC through their ultimate disposition. Amortization expense of purchase premium for the three and six months ended March 31, 2023 was $1,652 and $3,787, respectively. Amortization expense of purchase premium for the three and six months ended March 31, 2022 was $2,940 and $10,035, respectively. The purchase premium allocated to investments in equity securities will not amortize over the life of the equity securities through interest income and, assuming no subsequent change to the fair value of the equity securities acquired from GCIC and disposition of such equity securities at fair value, the Company will recognize a realized loss with a corresponding reversal of the unrealized depreciation upon disposition of the equity securities acquired from GCIC.

Income taxes: The Company has elected to be treated as a RIC under Subchapter M of the Code and operates in a manner so as to qualify for the tax treatment applicable to RICs. In order to qualify and be subject to tax as a RIC, among other things, the Company is required to meet certain source of income and asset diversification requirements and timely distribute dividends for U.S. federal income tax purposes to its stockholders of an amount generally at least equal to 90% of investment company taxable income, as defined by the Code and determined without regard to any deduction for dividends paid, for each tax year. The Company has made, and intends to continue to make, the requisite distributions to its stockholders, which will generally relieve the Company from U.S. federal income taxes with respect to all income distributed to its stockholders.

Depending on the level of taxable income earned in a tax year, the Company can determine to retain taxable income in excess of current year dividend distributions and distribute such taxable income in the next tax year. The Company may then be required to incur a 4% excise tax on such income. To the extent that the Company determines that its estimated current year annual taxable income, determined on a calendar year basis, could exceed estimated current calendar year dividend distributions, the Company accrues excise tax, if any, on estimated excess taxable income as taxable income is earned. For the three and six months ended March 31, 2023, $232 and $2,432, respectively, was recorded for U.S. federal excise tax. For the three and six months ended March 31, 2022, the Company did not record any U.S. federal excise tax.

The Company accounts for income taxes in conformity with ASC Topic 740 — Income Taxes (“ASC Topic 740”). ASC Topic 740 provides guidelines for how uncertain tax positions should be recognized, measured, presented and disclosed in financial statements. ASC Topic 740 requires the evaluation of tax positions taken in the course of preparing the Company’s tax returns to determine whether the tax positions are “more-likely-than-not” to be sustained by the applicable tax authority. Tax benefits of positions not deemed to meet the more-likely-than-not threshold would be recorded as a tax expense or tax benefit in the current year. It is the Company’s policy to recognize accrued interest and penalties related to uncertain tax benefits in income tax expense. There were no material unrecognized tax benefits or unrecognized tax liabilities related to uncertain income tax positions through March 31, 2023. The Company's tax returns for the 2019 through 2021 tax years remain subject to examination by U.S. federal and most state tax authorities.

The Company has adopted a dividend reinvestment plan (“DRIP”) that provides for reinvestment of any distributions the Company declares in cash on behalf of its stockholders, unless a stockholder elects to receive cash. As a result, if the Board authorizes and the Company declares a cash distribution, then stockholders who participate in the DRIP will have their cash distribution reinvested in additional shares of the Company’s common stock, rather than receiving the cash distribution. The Company expects to use newly issued shares under the guidelines of the DRIP if the Company’s shares are trading at a premium to net asset value. The Company can purchase shares in the open market in connection with the obligations under the plan, and in particular, if the Company’s shares are trading at a significant discount to net asset value (“NAV”) and the Company is otherwise permitted under applicable law to purchase such shares, the Company intends to purchase shares in the open market in connection with any obligations under the DRIP.

In the event the market price per share of the Company’s common stock on the date of a distribution exceeds the most recently computed NAV per share of the common stock, the Company will issue shares of common stock to participants in the DRIP at the greater of the most recently computed NAV per share of common stock or 95% of the current market price per share of common stock (or such lesser discount to the current market price per share that still exceeds the most recently computed NAV per share of common stock).

Share repurchase plan: The Company has a share repurchase program (the “Program”) which allows the Company to repurchase the Company’s outstanding common stock on the open market at prices below the Company’s NAV as reported in its most recently published consolidated financial statements. The Board most recently reapproved the Program in August 2022 and the Program is implemented at the discretion of management. Shares can be purchased from time to time at prevailing market prices, through open market transactions, including block transactions. The Program permits repurchases up to $150 million of the Company's common stock. Refer to Note 12 for more information on the share repurchases under the Program.

Equity Distribution Agreement: On May 28, 2021, the Company entered into an equity distribution agreement (the “Equity Distribution Agreement”), by and among the Company, the Investment Adviser, Golub Capital LLC and SMBC Nikko Securities America, Inc. (the “Placement Agent”), in connection with the sale by the Company of shares of its common stock, having an aggregate offering price of up to $250,000, in an “at the market offering,” in amounts and at times to be determined by the Company. Actual sales, if any, will depend on a variety of factors to be determined by the Company from time to time, including, among others, market conditions and the market price of the Company’s common stock. The Equity Distribution Agreement provides that the Company may offer and sell shares from time to time through the Placement Agent, or to it. Sales of the shares, if any, may be made in negotiated transactions or transactions that are deemed to be “at the market,” as defined in Rule 415 under the Securities Act of 1933, as amended, including sales made directly on The Nasdaq Global Select Market or any similar securities exchange or sales made to or through a market maker other than on a securities exchange, at prices related to the prevailing market prices or at negotiated prices. Pursuant to the terms of the Equity Distribution Agreement, the Placement Agent will receive a commission from the Company of up to 1.25% of the gross sales price of any shares sold through the Placement Agent under the Equity Distribution Agreement. Offering costs for the Equity Distribution Agreement are charged against the proceeds from equity offerings when proceeds are received. During the three and six months ended March 31, 2023 and 2022, the Company did not issue any shares of common stock under the Equity Distribution Agreement.

Deferred debt issuance costs: Deferred debt issuance costs represent fees and other direct incremental costs incurred in connection with the Company’s borrowings. As of March 31, 2023 and September 30, 2022, the Company had deferred debt issuance costs of $19,154 and $17,211, respectively. These amounts are amortized and included in interest expense in the Consolidated Statements of Operations over the estimated average life of the borrowings. Amortization expense for deferred debt issuance costs for the three and six months ended March 31,