X0508 4 2026-01-20 0 0000887343 COLUMBIA BANKING SYSTEM, INC. COLB 0001689701 Nixon Torran B C/O COLUMBIA BANKING SYSTEM, INC. 1301 A STREET TACOMA WA 98402 0 1 0 0 Senior Executive VP 0 Common Stock 2026-01-20 4 D 0 1717 0 D 103152 D Common Stock 2026-01-20 4 F 0 3873 28.35 D 99279 D Common Stock 3650 I by Nixon Family Trust Common Stock 1855 I by 401(k) Shares forfeited pursuant to the terms of the performance restricted stock units granted on February 21, 2023 and reported on the reporting person's Form 4 filed on February 21, 2023 (in accordance with Rule 16b-3(e)) due to the issuer's total shareholder return performance target not being met at target Represents withholding of shares of common stock to satisfy the reporting person's tax withholding obligations in connection with the vesting of previously issued restricted stock units. /s/ Andrea M. Newburn, Attorney-in-fact 2026-01-22