Columbia Banking System, Inc.

COLB·NASDAQ·$30.07Share Price as of 11/2·$7BMarket Cap as of 11/2

Financials

10-QQ2 ended 06/30/2608/04/26 10-QQ1 ended 03/31/2605/05/26 10-KFY 202502/26/26 10-QQ3 ended 09/30/2511/06/25 10-QQ2 ended 06/30/2508/06/25

Disclosures

8-KCurrent report10/27/26 8-KCurrent report10/22/26 8-KCurrent report09/30/26 8-KCurrent report08/14/26 8-KCurrent report07/30/26

Prospectuses and Registrations

S-8Registration of securities for employees09/02/25 424B3Prospectus06/16/25 S-4/ARegistration (business combination, amended)06/13/25 S-4Registration (business combination)05/28/25 S-3ASRAutomatic shelf registration12/20/24

Proxies

DEF 14ADefinitive proxy03/31/26 DEFA14AAdditional proxy materials03/31/26 DEF 14ADefinitive proxy04/03/25 DEFA14AAdditional proxy materials04/03/25 DEFA14AAdditional proxy materials04/08/24

Ownership

Form 4Insider transaction10/30/26 144Proposed sale of securities10/29/26 Form 4Insider transaction09/15/26 Form 4Insider transaction09/08/26 Form 4Insider transaction09/04/26

Other

11-KEmployee stock purchase plan report06/25/26 11-K/AEmployee stock purchase plan report (amended)06/16/26 11-KEmployee stock purchase plan report03/31/26 ARSAnnual report to shareholders03/31/26 42542507/11/25