Equity awards and tax withholding for Old Second Bancorp (OSBC) director

Rhea-AI Filing Summary

OLD SECOND BANCORP INC director Jill E. York reported a mix of equity award activity and tax-related share withholding. On February 17, she acquired 3,121 Restricted Stock Units (RSUs) as a grant under the Long Term Incentive Plan, with three-year cliff vesting.

On February 21, 3,077 RSUs were disposed of at $20.57 per share to cover tax liabilities upon vesting of a prior award, a non–open-market transaction. Following these events, she holds OSBC common stock both directly and indirectly, including shares held in trust with her spouse.

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^*

YORK JILL E

(Last) (First) (Middle)

C/O MB FINANCIAL INC

6111 NORTH RIVER ROAD

(Street)

ROSEMONT IL 60018

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
OLD SECOND BANCORP INC [ OSBC ]

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)
02/17/2026

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
Restricted Stock Units	02/17/2026		A		3,121(1)	A	$0	13,672	D
Restricted Stock Units	02/21/2026		F		3,077(2)	D	$20.57	10,595	D
Old Second Bancorp, Inc. Common Stock								3,077(3)	D
Old Second Bancorp, Inc. Common Stock								21,626	I	Held in Trust with spouse

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. These shares represent restricted stock units granted pursuant to the Old Second Bancorp, Inc. Long Term Incentive Plan. These shares have a three-year cliff vesting.

2. Represents shares vested upon the third anniversary of the date of grant previously reported and are now issued and added to the reporting person's common stock holdings outright.

3. These shares are held in Ms. York's name outright.

	/s/ Shirley Cantrell, Attorney-in-Fact	02/24/2026
	** 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 insider transactions did Jill E. York report for OLD SECOND BANCORP INC (OSBC)?

Jill E. York reported receiving 3,121 restricted stock units as an equity grant and a separate 3,077-share tax-withholding disposition tied to vested units. Both positions relate to Old Second Bancorp’s long-term incentive compensation structure for directors.

Was the 3,077-share transaction in OSBC stock an open-market sale by Jill E. York?

No, the 3,077 OSBC shares were disposed of to satisfy tax obligations on vested restricted stock units. This tax-withholding transaction is coded “F” and does not represent a discretionary open-market sale of shares by the director.

What is the nature of the 3,121 restricted stock units granted to Jill E. York at OSBC?

The 3,121 restricted stock units granted to Jill E. York are equity awards under Old Second Bancorp’s Long Term Incentive Plan. They vest on a three-year cliff schedule, aligning director compensation with longer-term company performance and service duration.

How are Jill E. York’s OSBC shares held after these Form 4 transactions?

After the reported transactions, Jill E. York holds Old Second Bancorp common stock both directly in her own name and indirectly in a trust with her spouse. The filing distinguishes direct ownership from indirect trust-held shares for transparency of beneficial ownership.

What does transaction code "F" mean in Jill E. York’s OSBC Form 4 filing?

Transaction code “F” indicates shares were used to pay an exercise price or tax liability. For Jill E. York, 3,077 Old Second Bancorp shares were withheld to cover taxes on vested restricted stock units, rather than being sold in an open market transaction.