[Form 4] Columbia Banking Systems Inc Insider Trading Activity

Rhea-AI Filing Summary

Columbia Banking System insider acquisition tied to Pacific Premier merger The reporting person, a company director, received 245,875 shares of Columbia common stock directly and 338,221 shares indirectly through the Gardner Family Trust as part of Columbia's acquisition of Pacific Premier Bancorp. Under the merger terms each Pacific Premier share was converted into 0.9150 Columbia shares, with fractional shares paid in cash. The filing discloses the share conversion and the closing prices on August 29: Columbia at $26.77 and Pacific Premier at $24.49.

Positive

• Clear disclosure of shares received from the merger, including direct and indirect holdings
• Material ownership increase for the reporting director (245,875 direct; 338,221 indirect)
• Merger conversion ratio disclosed (0.9150 Columbia shares per Pacific Premier share) and closing prices provided
• Fractional-share cash treatment disclosed, clarifying how non-integer conversions were handled

Negative

• None.

Insights

M&A Specialist

TL;DR: Merger consideration converted target shares into acquiror equity, materially increasing insider holdings.

The reported transactions are the direct outcome of a merger consideration formula converting Pacific Premier shares into Columbia shares at a 0.9150 exchange ratio. Receiving 245,875 shares directly plus 338,221 indirectly meaningfully increases the reporting person’s equity stake in Columbia and aligns insider interests with post-merger shareholders. The disclosure of closing prices provides transactional context but no cash consideration detail beyond fractional-share payments. This is a routine, legally required Section 16 disclosure following a corporate combination.

Corporate Governance Expert

TL;DR: Standard post-merger insider ownership update; governance implications are routine.

The Form 4 documents ownership change resulting from the merger; the reporting person is a director and the indirect holdings via a family trust are clearly disclosed. This preserves transparency around insider alignment after the transaction. There are no additional governance events, option exercises, or unusual transfer mechanisms disclosed. The filing meets Section 16 reporting norms without raising immediate governance flags.

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
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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^*

GARDNER STEVEN R

(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		245,875(1)	A	$0(1)	245,875	D
Common Stock	08/31/2025		A		338,221(1)	A	$0(1)	338,221	I	By The Gardner Family Trust

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.

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.

FAQ

What change in COLB ownership did the Form 4 report?

The Form 4 shows the reporting director acquired 245,875 Columbia shares directly and 338,221 indirectly via the Gardner Family Trust as consideration from the merger.

How were Pacific Premier shares converted into Columbia shares in the merger?

Each Pacific Premier share was converted into 0.9150 shares of Columbia common stock under the merger agreement; fractional shares were paid in cash.

What prices were cited in the filing for Columbia and Pacific Premier?

The filing notes closing prices on August 29: Columbia at $26.77 and Pacific Premier at $24.49.

Was the reported ownership direct, indirect, or both?

Both: direct ownership of 245,875 shares and indirect ownership of 338,221 shares through the Gardner Family Trust.

Does the Form 4 indicate any option exercises or derivative transactions?

No. Table II (derivative securities) shows no derivative transactions; the reported changes are non-derivative share acquisitions from the merger.