Form 4 Filing for Luis Machuca

This filing details transactions related to deferred compensation phantom stock for Luis Machuca, a director at Columbia Banking System, Inc. On September 14, 2026, 594 phantom stock units were acquired under the company's deferred compensation plan. These units represent a right to receive common stock in the future. The phantom stock was accrued under the Registrant's deferred compensation plan and will be settled in accordance with the plan's terms following Mr. Machuca's cessation of service as a director. The transaction indicates a grant or accrual of 594 shares with a reference price of $30.48 per share. Following this transaction, Mr. Machuca holds 49,560 shares in total. The filing is Form 4, indicating changes in beneficial ownership.