COLB

• Columbia Banking System, Inc. announced a quarterly cash dividend of $0.37 per common share.
• The dividend is payable on September 14, 2026, to shareholders of record as of August 28, 2026.
• The dividend was disclosed under Item 8.01 (Other Events) with a press release attached as Exhibit 99.1.
• Columbia Banking System is the parent company of Columbia Bank, headquartered in Tacoma, Washington.

8.01 Other Events · 9.01 Financial Statements and Exhibits

• Simone Lagomarsino, 64, was appointed to the Board of Directors of Columbia Banking System, Inc. and, subject to regulatory approval, to the board of its subsidiary Columbia Bank, effective September 1, 2026.
• Lagomarsino most recently served as President and board member of First Foundation Inc. until its sale on April 1, 2026, and previously as President and CEO of Luther Burbank Corporation.
• She will receive compensation consistent with the company's non-employee director program: a $95,000 annual cash retainer and a $115,000 annual equity retainer, prorated for partial-year service.
• She receives $100,000 annual deferred compensation payments from a plan maintained by Heritage Oaks Bank, which will conclude in 2032.
• A press release announcing the appointment was issued on July 30, 2026.

5.02 Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements · 7.01 Regulation FD Disclosure · 9.01 Financial Statements and Exhibits

• Net income was $208 million, with diluted EPS of $0.73; operating net income was $217 million, operating diluted EPS $0.76.
• Net interest income decreased to $589 million from $594 million in Q1 2026; net interest margin was 3.93%, down 3 bps.
• Net charge-offs were 0.25% of average loans (annualized), down from 0.30% in Q1 2026; provision was $27 million.
• Repurchased 6.6 million shares for $199 million; declared $0.37 per share dividend paid June 15, 2026.
• Deposit campaigns brought over $600 million in new deposits in the first campaign and about $650 million in the second through mid-July.

2.02 Results of Operations and Financial Condition · 7.01 Regulation FD Disclosure · 9.01 Financial Statements and Exhibits

• Columbia Banking System, Inc. will release Q2 2026 financial results on July 23, 2026, after market close.
• Management will discuss Q2 results and provide an update on recent activities, followed by a Q&A session.
• The announcement was made via press release on June 30, 2026, and furnished under Item 7.01 Regulation FD Disclosure.
• The press release is attached as Exhibit 99.1 to the Form 8-K.

7.01 Regulation FD Disclosure · 9.01 Financial Statements and Exhibits

• All twelve director nominees were elected, with votes for each director ranging from 231,293,225 (Luis F. Machuca) to 245,948,532 (Jaynie Miller Studenmund).
• Shareholders approved, on a non-binding advisory basis, the compensation of the company's named executive officers, with 240,301,679 votes for and 12,934,531 against.
• Shareholders ratified the appointment of Deloitte & Touche LLP as the independent registered public accounting firm for fiscal year ending December 31, 2026, with 269,295,913 votes for and 792,258 against.
• The report was filed under Item 5.07 to disclose the voting results of these matters submitted to a vote of security holders.

5.07 Submission of Matters to a Vote of Security Holders

• On May 15, 2026, Columbia Banking System, Inc. announced its Board of Directors approved a quarterly cash dividend of $0.37 per common share.
• The dividend is payable on June 15, 2026, to shareholders of record as of May 29, 2026.
• The announcement was made via a press release attached as Exhibit 99.1 to the Form 8-K.
• The filing was made under Item 8.01 (Other Events) to disclose the dividend declaration.

8.01 Other Events · 9.01 Financial Statements and Exhibits

• Net income for Q1 2026 was $192 million, with diluted EPS of $0.66; operating net income was $209 million, operating diluted EPS $0.72.
• Provision for credit losses increased to $28 million from $23 million; net charge-offs rose to 0.30% of average loans (annualized) from 0.25%.
• Total assets were $66.0 billion at March 31, 2026, down from $66.8 billion at December 31, 2025; deposits decreased to $53.5 billion from $54.2 billion.
• Repurchased $200 million of common stock (6.5 million shares at average price $30.74) and declared a $0.37 per share dividend paid March 16, 2026.

2.02 Results of Operations and Financial Condition · 7.01 Regulation FD Disclosure · 9.01 Financial Statements and Exhibits

• A conference call for investors and analysts will be held the same day at 2:00 p.m. PT (5:00 p.m. ET), with a live Q&A session.
• Management will discuss Q1 2026 financial results and provide an update on recent activities during the call.
• Participants can register for the call or listen-only audiocast via links provided in the press release; a replay will be available on the company's investor relations page.
• The announcement was made on March 31, 2026, and filed under Item 7.01 Regulation FD Disclosure with the press release attached as Exhibit 99.1.

7.01 Regulation FD Disclosure · 9.01 Financial Statements and Exhibits