UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

___________________________________________________

FORM 11-K

___________________________________________________

(Mark One)

x ANNUAL REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the fiscal year ended DECEMBER 31, 2023

OR

[ ] TRANSITION REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from             to             .

Commission File Number.....000-20288

___________________________________________________

A.    Full title of the plan and the address of the plan, if different from that of the issuer named below:

Umpqua Bank 401(k) and Profit Sharing Plan

B.    Name of issuer of the securities held pursuant to the plan and the address of its principal executive office:

Columbia Banking System, Inc.

1301 A Street

Tacoma, Washington 98402-2156

REQUIRED INFORMATION

1. Not Applicable

2. Not Applicable

3. Not Applicable

4. The Umpqua Bank 401(k) and Profit Sharing Plan (the Plan) is subject to the requirements of the Employee Retirement Income Security Act of 1974, as amended (ERISA). Furnished herewith are the financial statements and schedules of the Plan for the fiscal year ended December 31, 2023, prepared in accordance with the financial reporting requirements of ERISA.

Umpqua Bank

401(k) and Profit Sharing Plan

Financial Statements as of December 31, 2023 and 2022, and for the Year Ended December 31, 2023,

Supplemental Schedule as of December 31, 2023,

and Report of Independent Registered Public Accounting Firm

CONTENTS

		PAGE
REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM		1
FINANCIAL STATEMENTS
	Statements of net assets available for benefits as of December 31, 2023 and 2022	2
	Statement of changes in net assets available for benefits for the year ended December 31, 2023	3
	Notes to financial statements as of December 31, 2023 and 2022, and for the year ended December 31, 2023	4
SUPPLEMENTAL INFORMATION REQUIRED BY THE DEPARTMENT OF LABOR
	Schedule H, Part IV, Line 4(i) – Schedule of assets (held at end of year) as of December 31, 2023	12
	Schedule H, Part IV, Line 4(a) – Schedule of delinquent participant contributions for the year ended December 31, 2023	13
INDEX TO EXHIBITS
	EXHIBITS 23.1 - Consent of Independent Registered Public Accounting Firm	14
SIGNATURES		15
NOTE:
	All other schedules required by Section 2520.103-10 of the Department of Labor's Rules and Regulations for Reporting and Disclosure under the Employee Retirement Income Security Act of 1974 have been omitted because they are not applicable.

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

To the Plan Participants and Plan Administrator of

Umpqua Bank 401(k) and Profit Sharing Plan

Opinion on the Financial Statements

We have audited the accompanying statements of net assets available for benefits of the Umpqua Bank 401(k) and Profit Sharing Plan (the "Plan") as of December 31, 2023 and 2022, the related statement of changes in net assets available for benefits for the year ended December 31, 2023, and the related notes (collectively referred to as the "financial statements"). In our opinion, the financial statements present fairly, in all material respects, the net assets available for benefits of the Plan as of December 31, 2023 and 2022, and the changes in net assets available for benefits for the year ended December 31, 2023, in conformity with accounting principles generally accepted in the United States of America.

Basis for Opinion

These financial statements are the responsibility of the Plan's management. Our responsibility is to express an opinion on the Plan's financial statements based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and are required to be independent with respect to the Plan in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud. Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. We believe that our audits provide a reasonable basis for our opinion.

Report on Supplemental Schedules

The supplemental schedules of (1) assets (held at end of year) as of December 31, 2023, and (2) delinquent participant contributions for the year ended December 31, 2023 have been subjected to audit procedures performed in conjunction with the audit of the Plan's financial statements. The supplemental schedules are the responsibility of the Plan's management. Our audit procedures included determining whether the supplemental schedules reconcile to the financial statements or the underlying accounting and other records, as applicable, and performing procedures to test the completeness and accuracy of the information presented in the supplemental schedules. In forming our opinion on the supplemental schedules, we evaluated whether the supplemental schedules, including their form and content, are presented in compliance with the Department of Labor's Rules and Regulations for Reporting and Disclosure under the Employee Retirement Income Security Act of 1974. In our opinion, such schedules are fairly stated, in all material respects, in relation to the financial statements as a whole.

/s/ Deloitte & Touche LLP

Portland, Oregon

June 24, 2024

We have served as the auditor of the Plan since 2018.

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UMPQUA BANK 401(k) AND PROFIT SHARING PLAN

STATEMENTS OF NET ASSETS AVAILABLE FOR BENEFITS

DECEMBER 31, 2023 and 2022

				December 31,
(in thousands)				2023		2022
ASSETS
	Investments, at fair value			$	682,514	$	387,613
	Receivables
		Notes receivable from participants		11,111		6,651
		Employer contributions - match		1,711		1,119
		Participant contributions		—		725
			Total receivables	12,822		8,495
NET ASSETS AVAILABLE FOR BENEFITS				$	695,336	$	396,108

See accompanying notes.

2

UMPQUA BANK 401(k) AND PROFIT SHARING PLAN

STATEMENT OF CHANGES IN NET ASSETS AVAILABLE FOR BENEFITS

YEAR ENDED DECEMBER 31, 2023

ADDITIONS TO NET ASSETS ATTRIBUTED TO				(in thousands)
	Investment income
		Net appreciation in fair value of investments		$	69,279
		Dividends		6,958
		Interest		319
			Net investment income	76,556
	Interest income on notes receivable from participants			505
	Contributions
		Employer		12,070
		Participant		31,771
		Rollovers		4,670
			Total contributions	48,511
			Total additions	125,572
DEDUCTIONS FROM NET ASSETS ATTRIBUTED TO
	Benefits paid to participants			82,029
	Corrective distributions			42
	Administrative expenses			342
			Total deductions	82,413
CHANGE IN NET ASSETS				43,159
Transfer of assets from Columbia State Bank 401(k) plan				256,069
NET ASSETS AVAILABLE FOR BENEFITS
	Beginning of year			396,108
	End of year			$	695,336

See accompanying notes.

3

UMPQUA BANK 401(k) AND PROFIT SHARING PLAN

NOTES TO FINANCIAL STATEMENTS

AS OF DECEMBER 31, 2023 AND 2022, AND FOR THE YEAR ENDED DECEMBER 31, 2023

Note 1 – Description of Plan

The following description of theUmpqua Bank 401(k) and Profit Sharing Plan (the "Plan") provides only general information. Participants should refer to the Plan Agreement, as amended, for a more complete description of Plan provisions.

General – The Plan is a 401(k) salary deferral and profit sharing plan covering substantially all employees of Columbia Banking System, Inc. and Subsidiaries (the Company), and is subject to provisions of the Employee Retirement Income Security Act of 1974, as amended (ERISA). The Company is the Plan's sponsor and serves as Plan administrator.

Business Combination – On February 28, 2023, Umpqua Holdings Corporation (UHC) merged with and into Columbia Banking System, Inc (Columbia), with Columbia continuing as the surviving legal corporation. Promptly following the merger, Columbia’s wholly owned bank subsidiary, Columbia State Bank, merged with and into UHC’s wholly owned bank subsidiary, Umpqua Bank, with Umpqua Bank as the surviving bank. Upon completion of the merger, the combined company became Columbia Banking System, Inc. The UHC stock held by participants of the plan were converted to shares of Columbia stock at an exchange rate of 0.5958 for each share of UHC common stock held. Effective March 1, 2023, the employees of Columbia State Bank became employees of Umpqua Bank, however, they were ineligible to participate in the Plan and remained participants of the Columbia State Bank 401(k) plan. On July 25, 2023, the Columbia State Bank 401(k) plan merged into the Umpqua Bank 401(k) and Profit Sharing plan, with the Umpqua Bank 401(k) and Profit Sharing plan surviving. The Plan had an increase in net assets of $256.1 million as a result of the transfer of assets.

Eligibility – Employees of the Company are eligible to participate in the Plan upon reaching age 18. Employees are automatically enrolled into the Plan once they meet the eligibility criteria unless they choose to opt-out. Employees enter the Plan on scheduled enrollment dates following their completion of the eligibility requirements.

Contributions – Contributions are subject to regulatory limitations.

Employee deferrals –Participants may elect to contribute up to 80% of eligible compensation. In addition, participants may make voluntary Roth after-tax contributions or voluntary non-deductible after-tax contributions to the Plan. Participants may also roll over eligible amounts from other qualified plans.

Employer match –The Company may elect to make discretionary matching contributions to the Plan. Matching contributions are made each pay period. The Company matched 50% of employee contributions, up to 8% of eligible compensation deferred to the Plan for the year ended December 31, 2023.

Employer profit sharing –The Company may elect to make discretionary profit sharing contributions to the Plan. Participants must complete at least 1,000 hours of service during the Plan year and be employed as of the last day of the Plan year, to be eligible to receive any profit sharing contributions. Profit sharing contributions are allocated to participants in the same proportion as a participant's compensation bears to the total of all participants' compensation. There were no profit sharing contributions for the year ended December 31, 2023.

4

UMPQUA BANK 401(k) AND PROFIT SHARING PLAN

NOTES TO FINANCIAL STATEMENTS

AS OF DECEMBER 31, 2023 AND 2022, AND FOR THE YEAR ENDED DECEMBER 31, 2023

Note 1 – Description of Plan (continued)

Participant accounts –Each participant's account is credited with the participant's contribution and allocations of the Company's contributions and Plan earnings, and charged with an allocation of administrative expenses. Allocations are based on participant earnings or account balances, as defined. Participants direct the investment of their account balances into various investment options offered by the Plan. The Plan currently offers various registered investment company mutual funds, Company common stock, and common trusts, as investment options for participants. Previously, self-directed brokerage accounts were also available to participants. However, in 2023 the plan was updated to disallow new accounts and prevent investment updates to existing self-directed brokerage accounts.

Vesting – Participants are fully vested at all times in that portion of their accounts attributable to their own contributions and earnings or losses thereon. Vesting in Company contributions is based on years of service pursuant to the following vesting schedule. Participants who were part of acquired plans may have specific vesting schedules in accordance with those plans.

Years of service		Percentage
	Less than 1 year	—%
	1 year but less than 2	20%
	2 years but less than 3	40%
	3 years but less than 4	60%
	4 years but less than 5	80%
	5 years or more	100%

Notes receivable from participants – Participants may borrow from their accounts a minimum of $1,000 up to 50% of the participant's vested account, but not in excess of $50,000. Loans are secured by the balance of the participant's account and bear fixed, reasonable rates of interest, as determined by the Plan administrator. The maximum loan term is five years unless the loan qualifies as a home loan. Principal and interest are paid ratably through payroll deductions. As of December 31, 2023, the rates of interest on outstanding loans ranged from 3.25% to 9.50% with various maturities through 2047.

Payment of benefits – On termination of service due to death, disability, or retirement, a participant may elect to receive a lump-sum amount equal to the value of the participant's vested interest in his or her account balance, or annual installments over a period not more than the participant's life expectancy (or the assumed life expectancies of the participant and their beneficiary). For termination of service for other reasons, a participant may receive the value of the vested interest in his or her account as a lump-sum, fixed amount, fixed amount over time, withdrawal based on life expectancy, or fixed percentage withdrawal distribution.

Hardship withdrawals of the participants' contributions are permitted by the Plan. Hardship withdrawals must be approved by the Plan administrator and are limited to vested amounts of participants' contributions.

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UMPQUA BANK 401(k) AND PROFIT SHARING PLAN

NOTES TO FINANCIAL STATEMENTS

AS OF DECEMBER 31, 2023 AND 2022, AND FOR THE YEAR ENDED DECEMBER 31, 2023

Note 2 – Summary of Significant Accounting Policies

Basis of accounting – The financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America, using the accrual method of accounting.

Use of estimates – The preparation of financial statements in conformity with generally accepted accounting principles requires the use of estimates and assumptions that may affect certain reported amounts and disclosures. Accordingly, actual results could differ from those estimates.

Investment valuation – Investments are stated at fair value. Fair value is the price that would be received to sell an asset or paid to transfer a liability (i.e., the "exit price") in an orderly transaction between market participants at the measurement date. See Note 3 for discussion of fair value measurements.

Notes receivable from participants – Notes receivable from participants are measured at amortized cost, which represents unpaid principal balance plus accrued but unpaid interest. Delinquent notes receivable from participants are recorded as distributions based on the terms of the Plan Document.

Income recognition – Purchases and sales of securities are recorded on a trade-date basis. Dividends are recorded on the ex-dividend date. Interest income is recorded on the accrual basis. The net appreciation in fair value of investments consists of both the realized gains or losses and unrealized depreciation and appreciation of those investments.

Payment of benefits – Benefit payments are recorded when paid.

Contributions - Contributions are recognized during the period in which the respective payroll deductions are made. Employer and Participant contributions are invested directly in appropriate funds based upon Participant elections made at the date of enrollment or through authorized changes in elections.

Expenses – Administrative expenses such as legal and accounting fees are paid by the Company; however, they may be paid with Plan forfeitures. Transaction fees and investment management fees are deducted directly from the participant's account.

Forfeitures – Forfeitures are the nonvested portion of a participant's account that are lost upon termination of employment. Forfeitures are retained in the Plan and will be used to reduce future Company contributions, and eligible, reasonable administrative expenses. As of December 31, 2023 and 2022, forfeited non-vested accounts totaled $77,000 and $81,000, respectively. During 2023, the Company used $1.1 million of forfeitures to fund 2023 match contributions.

Subsequent events –Subsequent events are events or transactions that occur after the statement of net assets available for benefits date but before financial statements are issued. The Plan recognizes in the financial statements the effects of all subsequent events that provide additional evidence about conditions that existed at the date of the statement of net assets available for benefits, including the estimates inherent in the process of preparing the financial statements. The Plan's financial statements do not recognize subsequent events that provide evidence about conditions that did not exist at the date of the statement of net assets available for benefits but arose after the statement of net assets available for benefits date and before financial statements were issued.

6

UMPQUA BANK 401(k) AND PROFIT SHARING PLAN

NOTES TO FINANCIAL STATEMENTS

AS OF DECEMBER 31, 2023 AND 2022, AND FOR THE YEAR ENDED DECEMBER 31, 2023

Note 3 – Fair Value Measurements

The fair value framework provides a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (level 1 measurement) and the lowest priority to unobservable inputs (level 3 measurements).

The asset or liability's fair value measurement level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. Valuation techniques maximize the use of observable inputs and minimize the use of unobservable inputs.

The following is a description of the valuation methodologies used for assets measured at fair value.

Money markets and other cash equivalents – Valued at quoted market prices, which represent the net asset value (NAV) of shares held by the Plan at year end. Money market and other cash equivalents are generally classified within level 1 of the valuation hierarchy.

Registered investment companies (mutual funds) – Valued at quoted market prices, which represent the NAV of shares held by the Plan at year end. Mutual funds are generally classified within level 1 of the valuation hierarchy.

Common stock – Valued at the closing price reported on the active market on which the individual securities are traded. Common stock is generally classified within level 1 of the valuation hierarchy.

Self-directed brokerage– The self-directed brokerage accounts include money markets, mutual funds, and common stock, which are valued within the brokerage account using level 1 valuation inputs.

Collective trusts – Units held in collective trusts are valued using the NAV of the funds. The NAV is used as a practical expedient to estimate fair value. The NAV is based on the fair value of the underlying assets owned by the fund, minus its liabilities, and then divided by the number of units outstanding. Participant transactions (purchases and sales) may occur daily at NAV. Investments in collective investment funds are redeemable daily at NAV, which is the readily determinable fair value. The common collective trust funds measured at NAV have not been classified in the fair value hierarchy.

The Plan invests in fourteen collective investment trusts, twelve of which are target date funds for investors expecting to retire around the year indicated in each fund's name. The price per share is quoted on a private market that is not active. One of the remaining collective trusts that the Plan invests in is the Putnam Stable Value Fund 15, which is designed to provide preservation of capital and achieve high current income through a diversified portfolio. The fund invests primarily in security-backed investment contracts issued by insurance companies and other financial institutions, fixed income securities, and money market funds. The remaining collective trust that the Plan invests in is the Cohen & Steers U.S. Realty Fund Class RS, which seeks to maximize total return by outperforming its benchmark, FTSE Nareit All Equity REITs Index, over the long term. The fund invests in a diversified portfolio of common stocks of real estate companies and other permitted investments. It invests in publicly traded real estate companies that own income-producing properties or land, including real estate investment trusts (REITs) and real estate corporations, primarily domiciled in the United States.

7

UMPQUA BANK 401(k) AND PROFIT SHARING PLAN

NOTES TO FINANCIAL STATEMENTS

AS OF DECEMBER 31, 2023 AND 2022, AND FOR THE YEAR ENDED DECEMBER 31, 2023

Note 3 – Fair Value Measurements (continued)

The valuation methods used by the Plan may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. Furthermore, although the Plan believes its valuation methods are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different fair value measurement at the reporting date.

The following tables disclose by level, the fair value hierarchy, of the Plan's assets at fair value:

		Investment Assets at Fair Value as of December 31, 2023
(in thousands)		Level 1		Level 2		Level 3		Total
Money markets and other cash equivalents		$	4	$	—	$	—	$	4
Registered investment companies		304,850		—		—		304,850
Common stock - Columbia Banking System, Inc.		15,977		—		—		15,977
Self-directed brokerage accounts		6,535		—		—		6,535
	Total assets in the fair value hierarchy	$	327,366	$	—	$	—	$	327,366
Investments measured at NAV (1)
	Collective trusts							$	355,148
Total investments at fair value								$	682,514
(1)	Certain investments that were measured at net asset value per share have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the line items presented in the statement of net assets available for benefits.

		Investment Assets at Fair Value as of December 31, 2022
(in thousands)		Level 1		Level 2		Level 3		Total
Money markets and other cash equivalents		$	9,218	$	—	$	—	$	9,218
Registered investment companies		126,442		—		—		126,442
Common stock – Umpqua Holdings Corp.		10,358		—		—		10,358
Self-directed brokerage accounts		5,283		—		—		5,283
	Total assets in the fair value hierarchy	$	151,301	$	—	$	—	$	151,301
Investments measured at NAV (1)
	Collective trusts							$	236,312
Total investments at fair value								$	387,613
(1)	Certain investments that were measured at net asset value per share have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the line items presented in the statement of net assets available for benefits.

8

UMPQUA BANK 401(k) AND PROFIT SHARING PLAN

NOTES TO FINANCIAL STATEMENTS

AS OF DECEMBER 31, 2023 AND 2022, AND FOR THE YEAR ENDED DECEMBER 31, 2023

Note 3 – Fair Value Measurements (continued)

The following tables summarize investments for which fair value is measured using the NAV per share practical expedient:

	Fair		Unfunded	Redemption	Redemption
December 31, 2023	Value		Commitments	Frequency	Notice Period
	(in thousands)
Collective trusts	$	355,148	None	Daily	N/A

	Fair		Unfunded	Redemption	Redemption
December 31, 2022	Value		Commitments	Frequency	Notice Period
	(in thousands)
Collective trusts	$	236,312	None	Daily	N/A

Note 4 – Tax Status

The Internal Revenue Service (IRS) has determined and informed the Company by a letter dated June 30, 2020, that the Plan and related trust are designed in accordance with applicable sections of the Internal Revenue Code (IRC). Although the Plan has been amended since receiving the determination letter, the Company and Plan management believes that the Plan is designed and is currently being operated in compliance with the applicable requirements of the IRC, and the Plan and related trust continue to be tax-exempt.

During 2023, the Company identified operational errors involving a greater number of participant loans than was permissible in accordance with the terms of the plan loan policy. On behalf of the Plan, the Company is in the process of filing a correction under the IRS Voluntary Correction Program (VCP) to receive a formal statement from the IRS that neither the failure nor the correction of the failure will have any adverse tax-qualification implications for the Plan.

Note 5 – Risks and Uncertainties

The Plan invests in various investment securities. Investment securities are exposed to various risks, such as interest rate, market volatility, and credit risk. It is reasonably possible that, given the level of risk associated with investment securities, changes in the near term could materially affect a participant's account balance and the amounts reported in the financial statements.

9

UMPQUA BANK 401(k) AND PROFIT SHARING PLAN

NOTES TO FINANCIAL STATEMENTS

AS OF DECEMBER 31, 2023 AND 2022, AND FOR THE YEAR ENDED DECEMBER 31, 2023

Note 6 – Related Party Transactions and Exempt Party-in-Interest Transactions

Plan investments in 2022 included shares of UHC stock; however, upon completion of the merger, the combined company became Columbia Banking System, Inc. On the merger date, UHC stock held by participants of the plan totaling $10.4 million were converted to shares of Columbia Banking System, Inc. stock at an exchange rate of 0.5958 for each share of UHC common stock held. Accordingly, plan investments for 2023 include shares of Columbia Banking System, Inc. stock, which is the common stock of the Company. As of December 31, 2023, the Plan's investment in the Company's common stock was $16.0 million, compared to $10.4 million as of December 31, 2022. The increase was mainly due to approximately $6.4 million associated with the balance of the Columbia State Bank 401(k) plan that merged into the Umpqua Bank 401(k) and Profit Sharing plan, in addition to employee and employer contributions of $767,000, as well as interest and dividends of $679,000. The increase was partially offset by benefit payment distributions of $1.9 million. During the year ended December 31, 2022, the Plan's investment in the Company's common stock decreased by $321,000, mainly due to unrealized and realized losses of $813,000 and benefit payment distributions of $557,000, partially offset by employee and employer contributions of $686,000, as well as interest and dividends of $481,000. Certain Plan investments are shares of mutual funds managed by Fidelity Trust Management Company, which is the trustee of the Plan. These transactions qualify as exempt party-in-interest transactions.

For the 2023 Plan year, the Company identified participant contributions totaling $2,460 that may have been remitted to the trustee later than required by Department of Labor (DOL) regulations. The Company will file Form 5330 with the IRS and pay the excise tax due on the transactions, if required. In addition, participant accounts will be credited as necessary in accordance with DOL guidelines.

Note 7 – Plan Termination

Although it has not expressed any intention to do so, the Company has the right to terminate the Plan and discontinue its contributions at any time. If the Plan is terminated, amounts allocated to a participant's account would become fully vested.

10

SUPPLEMENTAL INFORMATION

REQUIRED BY THE DEPARTMENT OF LABOR

UMPQUA BANK 401(k) AND PROFIT SHARING PLAN

EIN: 93-1261319

PLAN NO. 001

SCHEDULE H, PART IV, LINE 4(i) – SCHEDULE OF ASSETS (HELD AT END OF YEAR)

DECEMBER 31, 2023

(a)	(b) Identity of Issue, Borrower, Lessor, or Similar Party	(c) Description of Investment, Including Maturity Date, Rate of Interest, Collateral, Par, or Maturity Value	(d) Cost	(e) Current Value
				(in thousands)
	Vanguard Target 2030	Collective trust	**	$	49,810
	Vanguard Target 2040	Collective trust	**	46,142
	Vanguard Target 2025	Collective trust	**	44,972
	Vanguard Target 2045	Collective trust	**	44,573
	Vanguard Target 2035	Collective trust	**	39,233
	Putnam Stable Value	Collective trust	**	35,724
	Vanguard Target 2050	Collective trust	**	27,939
	Vanguard Target 2020	Collective trust	**	22,932
	Vanguard Target 2055	Collective trust	**	22,538
	Vanguard Target Inc.	Collective trust	**	9,354
	Cohen & Steers U.S. Realty Fund Class RS	Collective trust	**	5,727
	Vanguard Target 2060	Collective trust	**	4,219
	Vanguard Target 2065	Collective trust	**	1,811
	Vanguard Target 2070	Collective trust	**	174
	Total collective trusts			355,148
*	Fidelity 500 Index Fund	Registered investment company	**	68,547
*	Fidelity Blue Chip Growth Fund Class K6	Registered investment company	**	41,588
	Vanguard Mid-Cap Value Index Fund Admiral Shares	Registered investment company	**	30,715
	Vanguard Value Index Fund Institutional Shares	Registered investment company	**	26,282
	T. Rowe Price Diversified Mid-Cap Growth Fund I Class	Registered investment company	**	25,433
*	Fidelity Small Cap Index Fund	Registered investment company	**	24,691
*	Fidelity Total International Index Fund	Registered investment company	**	14,593
	Dodge & Cox Income Fund Class X	Registered investment company	**	14,267
	T. Rowe Price Capital Appreciation Fund I Class	Registered investment company	**	12,809
*	Fidelity Mid Cap Index Fund	Registered investment company	**	10,744
	Dodge & Cox International Stock Fund Class X	Registered investment company	**	9,726
*	Fidelity U.S. Bond Index Fund	Registered investment company	**	5,676
*	Fidelity Inflation-Protected Bond Index Fund	Registered investment company	**	5,575
	BlackRock High Yield Bond Portfolio Class K	Registered investment company	**	5,548
	Vanguard International Growth Fund Admiral Shares	Registered investment company	**	4,852
	John Hancock Small Cap Core Fund Class R6	Registered investment company	**	3,804
	Total registered investment companies			304,850
	Vanguard Federal Money Market Fund Investor Shares	Money market fund	**	4
*	Columbia Banking System, Inc.	Common stock	**	15,977
	BrokerageLink accounts	Various investments, including registered investment companies, common stocks, money market funds and cash	**	6,535
*	Participant loans	3.25% – 9.50%, various maturities through 2047	$—	11,111
				$	693,625
* Indicates party-in-interest
** Information is not required as investments are participant directed.

See accompanying Report of Independent Registered Public Accounting Firm.

12

UMPQUA BANK 401(k) AND PROFIT SHARING PLAN
EIN: 93-1261319
PLAN NO. 001
SCHEDULE H, LINE 4(a) - SCHEDULE OF DELINQUENT PARTICIPANT CONTRIBUTIONS
FOR THE YEAR ENDED DECEMBER 31, 2023
Participant Contributions Transferred Late to Plan		Total that Constitute Nonexempt Prohibited Transactions
Check here if Late Participant Loan Repayments are included ☐		Contributions Not Corrected		Contributions Corrected Outside VFCP		Contributions Pending Correction in VFCP		Total Fully Corrected Under VFCP and PTE 2002-51
$	2,460	$	2,460	$	—	$	—	$	—

13

INDEX TO EXHIBITS

Exhibit No.Description

23.1Consent of Independent Registered Public Accounting Firm

14

SIGNATURES

Pursuant to the requirements of the Securities and Exchange Act of 1934, the Plan Administrator has duly caused this annual report to be signed on its behalf by the undersigned hereunto duly authorized.

	Umpqua Bank 401(k) and Profit Sharing Plan
Date: June 24, 2024
	/s/ Lisa M. White
	Lisa M. White
	Corporate Controller and Principal Accounting Officer

15