Drew K. Anderson - 13 Mar 2026 Form 4 Insider Report for COLUMBIA BANKING SYSTEM, INC. (COLB)

Role: EVP Chief Admin Officer
Signature: /s/ Andrea M. Newburn, Attorney-in-fact
Issuer symbol: COLB
Transactions as of: 13 Mar 2026
Net transactions value: $0
Form type: 4
Filing time: 17 Mar 2026, 20:24:10 UTC
Previous filing: 02 Mar 2026
SEC: View on sec.gov

Reporting Owners (1)

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	17 Mar 2026	0001955918

Transactions Table

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Ownership	Footnotes
transaction	COLB	Common Stock	Options Exercise		+2,506	+12%	$26.23^*	23,184	13 Mar 2026	Direct
transaction	COLB	Common Stock	Tax liability		-1,215	-5.2%	$26.23^*	21,969	13 Mar 2026	Direct

Derivative Securities (e.g., puts, calls, warrants, options, convertible securities)

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Underlying Class	Amount	Exercise Price	Ownership	Footnotes
transaction	COLB	Restricted Stock Unit	Options Exercise		-2,506	-4.7%	$0.000000^*	50,607	13 Mar 2026	Common Stock	2,506		Direct	F1

* An asterisk sign (*) next to the price indicates that the price is likely invalid.

Explanation of Responses:

Id	Content
F1	Restricted Stock Units convert into common stock on a one-for-one basis. On February 25, 2025, the reporting person was granted 7,518 Restricted Stock Units, which vest in three annual installments beginning on March 13, 2026.