| Name | Relationship | Address | Signature | Signature date | CIK |
|---|---|---|---|---|---|
| Anderson Drew K | EVP Chief Admin Officer | C/O COLUMBIA BANKING SYSTEM, INC., 1301 A STREET, TACOMA | /s/ Andrea M. Newburn, Attorney-in-fact | 02 Mar 2026 | 0001955918 |
| Type | Sym | Class | Transaction | Value $ | Shares | Change % | * Price $ | Shares After | Date | Ownership | Footnotes |
|---|---|---|---|---|---|---|---|---|---|---|---|
| transaction | COLB | Common Stock | Tax liability | $51,438 | -1,808 | -8% | $28.45 | 20,678 | 01 Mar 2026 | Direct |