[Form 4] Columbia Banking Systems Inc Insider Trading Activity

Rhea-AI Filing Summary

Mitchell M. Christian, a director of Columbia Banking System, Inc. (COLB), reported acquisitions totaling 37,960 shares of Columbia common stock. On 08/31/2025 he received 35,755 shares as part of Columbia's acquisition of Pacific Premier Bancorp, Inc., where each Pacific Premier share converted into 0.9150 Columbia shares; fractional shares were paid in cash. The filing shows closing prices on 08/29/2025 of Columbia at $26.77 and Pacific Premier at $24.49. Separately, on 09/02/2025 he was granted 2,205 restricted shares that vest on 05/15/2026. All reported holdings are direct beneficial ownership and the transactions are coded as acquisitions with a reported price of $0, reflecting conversion/award mechanics.

Insights

Financial Analyst

TL;DR: Routine insider share increase from merger conversion and restricted awards; no cash purchase indicated.

The Form 4 documents a non-cash increase in direct holdings for a director due to a merger conversion and restricted stock grants. The 35,755 shares from the Pacific Premier transaction reflect the agreed exchange ratio of 0.9150 Columbia shares per Pacific Premier share; the filing appropriately reports the transaction as an acquisition with a reported price of $0 because consideration was non-cash or paid as fractional share cash-outs. The additional 2,205 restricted shares vesting on 05/15/2026 create a near-term vesting milestone to monitor for potential future sales or continuing ownership alignment.

Corporate Governance Expert

TL;DR: Disclosure is standard and timely, showing increased director ownership post-merger and a forthcoming restricted stock vesting.

The filing appears complete for Section 16 reporting: it identifies the reporting person, relationship as a director, transaction dates, acquisition codes, and the nature of the restricted awards. The merger-related conversion and the vesting schedule are disclosed, supporting transparency around insider holdings. There are no indications in this filing of unusual transaction structures or omissions based on the provided content.

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

MITCHELL M CHRISTIAN

(Last) (First) (Middle)

C/O COLUMBIA BANKING SYSTEM, INC.

1301 A STREET

(Street)

TACOMA WA 98402

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
COLUMBIA BANKING SYSTEM, INC. [ COLB ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
08/31/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	08/31/2025		A		35,755(1)	A	$0(1)	35,755	D
Common Stock	09/02/2025		A		2,205(2)	A	$0(2)	37,960	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. Acquired in connection with Columbia Banking System, Inc.'s ("Columbia") acquisition of Pacific Premier Bancorp, Inc. ("Pacific Premier") on August 31, 2025. Pursuant to the merger agreement, each issued and outstanding share of Pacific Premier common stock held by the reporting person was converted into the right to receive 0.9150 of a share of Columbia common stock. All fractional share holdings were paid in cash. On August 29, 2025, the closing price of Columbia common stock was $26.77, and the closing price of Pacific Premier common stock was $24.49.

2. Restricted stock awards that vest in their entirety on May 15, 2026.

Remarks:

	/s/ Lisa M. White, Attorney-in-fact	09/03/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.