Form 8-K

8-K — COLUMBIA BANKING SYSTEM, INC.

Accession: 0000887343-26-000116

Filed: 2026-03-31

Period: 2026-03-31

CIK: 0000887343

SIC: 6022 (STATE COMMERCIAL BANKS)

Item: Regulation FD Disclosure

Item: Financial Statements and Exhibits

Documents

8-K — colb-20260331.htm (Primary)

EX-99.1 (colbex991q12026earningscal.htm)

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8-K

8-K (Primary)

Filename: colb-20260331.htm · Sequence: 1

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities and Exchange Act of 1934

Date of Report: March 31, 2026

(Date of earliest event reported)

Columbia Banking System, Inc.

(Exact Name of Registrant as Specified in Its Charter)

Washington 000-20288 91-1422237

(State or Other Jurisdiction of Incorporation or Organization)

(Commission File Number)

(I.R.S. Employer Identification Number)

1301 A Street

Tacoma, Washington 98402-4200

(address of Principal Executive Offices)(Zip Code)

(253) 305-1900

(Registrant's Telephone Number, Including Area Code)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

[ ☐ ] Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

[ ☐ ] Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

[ ☐ ] Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

[ ☐ ] Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

TITLE OF EACH CLASS TRADING SYMBOL NAME OF EXCHANGE

Common Stock, No Par Value COLB The Nasdaq Stock Market LLC

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company [ ☐]

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act [ ]

Item 7.01 Regulation FD Disclosure

On March 31, 2026, Columbia Banking System, Inc. announced that it will conduct a quarterly earnings conference call on Thursday, April 23, 2026, at 2:00 p.m. PT (5:00 p.m. ET). During the call, management will discuss Columbia’s first quarter 2026 financial results and provide an update on recent activities. The press release announcing the conference call information is attached as Exhibit 99.1 and incorporated herein by reference.

Item 9.01 Financial Statements and Exhibits

(d) Exhibits.

99.1 Press Release Announcing Quarterly Earnings Conference Call

104 Cover Page Interactive Data File (embedded within the Inline XBRL document)

SIGNATURES

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

COLUMBIA BANKING SYSTEM, INC.

(Registrant)

Dated: March 31, 2026

By:/s/ Kumi Yamamoto Baruffi

Kumi Yamamoto Baruffi

Executive Vice President, General Counsel

EX-99.1

Filename: colbex991q12026earningscal.htm · Sequence: 2

Document

Columbia Banking System Announces Date of First Quarter 2026 Earnings Release and Conference Call

TACOMA, Wash., Mar 31, 2026 – Columbia Banking System, Inc. (“Columbia” Nasdaq: COLB), parent company of Columbia Bank, today announced it will release first quarter 2026 financial results on Thursday, April 23, 2026, after market close. The Company will host a conference call for investors and analysts at 2:00 p.m. PT (5:00 p.m. ET) that same day. During the call, management will discuss Columbia’s first quarter 2026 financial results and provide an update on recent activities. There will be a live question-and-answer session following the presentation. Participants may register for the call using the link below to receive dial-in details and their own unique PINs or register for the listen-only audiocast. It is recommended you join 10 minutes prior to the start time.

Join the audiocast: https://edge.media-server.com/mmc/p/y2c5ea4c/

https://register-conf.media-server.com/register/BI6f2e58fad341429a8b85e604aa895766

Access the replay through the Company’s investor relations page under the “News & Market Data-Event Calendar” section: https://www.columbiabankingsystem.com

About Columbia

Columbia Banking System, Inc. (Nasdaq: COLB) is headquartered in Tacoma, Washington and is the parent company of Columbia Bank, an award-winning western U.S. regional bank. Columbia Bank is the largest bank headquartered in the Northwest and one of the largest banks headquartered in the West with offices in Arizona, California, Colorado, Idaho, Nevada, Oregon, Texas, Utah, and Washington. Columbia Bank combines the resources, sophistication, and expertise of a national bank with a commitment to deliver superior, personalized service. The bank supports consumers and businesses through a full suite of services, including retail and commercial banking, Small Business Administration lending, institutional and corporate banking, and equipment leasing. Columbia Bank customers also have access to comprehensive investment and wealth management expertise as well as healthcare and private banking through Columbia Wealth Management. Learn more at www.columbiabankingsystem.com.

Investor Relations Contact:

Jacquelynne “Jacque” Bohlen

ir@columbiabank.com

(503) 727-4100

Note Regarding Forward Looking Statements

This news release includes forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, which can be identified by words such as "may," "expected," "anticipate," "continue," or other comparable words. In addition, all statements other than statements of historical facts that address activities that Columbia expects or anticipates will or may occur in the future are forward-looking statements. Readers are encouraged to read the SEC reports of Columbia, particularly its Annual Report on Form 10-K for the Fiscal Year ended December 31, 2025, for meaningful cautionary language discussing why actual results may vary materially from those anticipated by management.

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