OSBC · Old Second Bancorp Inc

The reporting person moved 3,077 shares that were previously held in his account from within Old Second Bancorp, Inc., as reported on a Form 4 filing dated February 24, 2026, to his brokerage account. The total shown reflects the addition of the 3,077 shares when combined with the sale of 25,000 shares.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $25.50 to $25.60, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on May 1, 2026.

The price reported is a weighted average price. The transactions were effected at prices ranging from $25.48 to $25.79.

Included in this total are 303,251 shares held at a brokerage firm in the reporting person's name and 148 shares held jointly with spouse outright.

The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on May 1, 2026.

The price reported is a weighted average price. The transactions were effected at prices ranging from $25.30 to $25.6050.

Included in this total are 8,687 shares held with a broker and 11,430 shares held in Mr. Lyons' name outright.

Of this total, 1 share was allocated during the second quarter pursuant to the Old Second Bancorp, Inc. Employees Profit Sharing Plan and Trust. Information herein was provided by the Plan Trustee as of 6-30-26.

Of this total, 111 shares were allocated during the second quarter pursuant to the Old Second Bancorp, Inc. Salary and Savings Plan. Information was provided herein by the Plan Trustee as of 6-30-26.

Of this total, 14 shares were allocated during the second quarter pursuant to the Old Second Bancorp, Inc. Salary and Savings Plan. Information was provided herein by the Plan Trustee as of 6-30-26.

Of this total, 37 shares were allocated during the second quarter pursuant to the Old Second Bancorp, Inc. Employee Salary and Savings Plan. Information herein was provided by the Plan Trustee as of 6-30-26.

Of this total, 34 shares were allocated during the second quarter pursuant to the Old Second Bancorp, Inc. Salary & Savings Plan. Information herein was provided by the Plan Trustee as of 6-30-26.

Of this total, 42 shares were allocated during the second quarter pursuant to the Old Second Bancorp, Inc. Employee Salary and Savings Plan. Information herein was provided by the Plan Trustee as of 6-30-26.

Of this total, 21 shares were allocated during the second quarter pursuant to the Old Second Bancorp, Inc. Employees Profit Sharing Plan and Trust. Information herein was provided by the Plan Trustee as of 6-30-26.

Of this total, 369 shares were allocated during the first quarter pursuant to the Old Second Bancorp, Inc. Salary and Savings Plan. Information was provided herein by the Plan Trustee as of 3-31-26.

Of this total, 1 share was allocated during the first quarter pursuant to the Old Second Bancorp, Inc. Employees Profit Sharing Plan and Trust. Information herein was provided by the Plan Trustee as of 3-31-26.

Of this total, 35 shares were allocated during the first quarter pursuant to the Old Second Bancorp, Inc. Employee Salary and Savings Plan. Information herein was provided by the Plan Trustee as of 3-31-26.

Of this total, 13 shares were allocated during the first quarter pursuant to the Old Second Bancorp, Inc. Salary and Savings Plan. Information was provided herein by the Plan Trustee as of 3-31-26.

Of this total, 253 shares were allocated during the first quarter pursuant to the Old Second Bancorp, Inc. Salary and Savings Plan. Information was provided herein by the Plan Trustee as of 3-31-26.

Of this total, 43 shares were allocated during the first quarter pursuant to the Old Second Bancorp, Inc. Employee Salary and Savings Plan. Information herein was provided by the Plan Trustee as of 3-31-26.

Of this total, 22 shares were allocated during the first quarter pursuant to the Old Second Bancorp, Inc. Employees Profit Sharing Plan and Trust. Information herein was provided by the Plan Trustee as of 3-31-26.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $19.37 to $19.40, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

Represents shares withheld by the issuer to satisfy applicable tax withholding obligations in connection with the vesting of 9,201 previously reported performance-based restricted stock units, the remaining shares of which were issued and added to the reporting person's common stock holdings.

Included in this total are 9,919 shares in the reporting person's name outright and 63,135 shares held in the reporting person's name in a brokerage account.

Shares delivered to the reporting person pursuant to vesting of performance-based restricted stock units granted under the Old Second Bancorp, Inc. 2019 Equity Incentive Plan, as Amended and Restated and vested upon achievement of performance goals for the applicable performance period. The reporting person reported an acquisition of 25,038 on Form 4 filed February 21, 2023, which represented the number of shares that would be delivered if target performance was achieved during the performance period. Actual performance exceeded the target performance for the performance period which resulted in an additional grant of 18,780 shares.

Represents shares withheld by the issuer to satisfy applicable tax withholding obligations in connection with the vesting of 14,432 previously reported performance-based restricted stock units, the remaining shares of which were issued and added to the reporting person's common stock holdings.

Shares delivered to the reporting person pursuant to vesting of performance-based restricted stock units granted under the Old Second Bancorp, Inc. 2019 Equity Incentive Plan, as Amended and Restated and vested upon achievement of performance goals for the applicable performance period. The reporting person reported an acquisition of 2,585 on Form 4 filed February 21, 2023, which represented the number of shares that would be delivered if target performance was achieved during the performance period. Actual performance exceeded the target performance for the performance period which resulted in an additional grant of 1,938 shares.

Represents shares withheld by the issuer to satisfy applicable tax withholding obligations in connection with the vesting of 43,818 previously reported performance-based restricted stock units, the remaining shares of which were issued and added to the reporting person's common stock holdings.

Included in this total are 30,980 shares held in the reporting person's name outright; 347,271 shares held with a brokerage firm and 148 shares held jointly with spouse.

Represents shares withheld by the issuer to satisfy applicable tax withholding obligations in connection with the vesting of 15,657 previously reported performance-based restricted stock units, the remaining shares of which were issued and added to the reporting person's common stock holdings.

Included in this total are 75,300 shares held by the reporting person jointly with a spouse at a brokerage firm and 85,101 shares held jointly with spouse outright,

Represents shares withheld by the issuer to satisfy applicable tax withholding obligations in connection with the vesting of 4,523 previously reported performance-based restricted stock units, the remaining shares of which were issued and added to the reporting person's common stock holdings.

Included in this total are 4,677 shares held outright in the reporting person's name and 24,874 shares held with a brokerage firm.

Shares delivered to the reporting person pursuant to vesting of performance-based restricted stock units granted under the Old Second Bancorp, Inc. 2019 Equity Incentive Plan, as Amended and Restated and vested upon achievement of performance goals for the applicable performance period. The reporting person reported an acquisition of 8,946 on Form 4 filed February 21, 2023, which represented the number of shares that would be delivered if target performance was achieved during the performance period. Actual performance exceeded the target performance for the performance period which resulted in an additional grant of 6,711 shares.

Shares delivered to the reporting person pursuant to vesting of performance-based restricted stock units granted under the Old Second Bancorp, Inc. 2019 Equity Incentive Plan, as Amended and Restated and vested upon achievement of performance goals for the applicable performance period. The reporting person reported an acquisition of 8,246 on Form 4 filed February 21, 2023, which represented the number of shares that would be delivered if target performance was achieved during the performance period. Actual performance exceeded the target performance for the performance period which resulted in an additional grant of 6,186 shares.

Shares delivered to the reporting person pursuant to vesting of performance-based restricted stock units granted under the Old Second Bancorp, Inc. 2019 Equity Incentive Plan, as Amended and Restated and vested upon achievement of performance goals for the applicable performance period. The reporting person reported an acquisition of 5,256 on Form 4 filed February 21, 2023, which represented the number of shares that would be delivered if target performance was achieved during the performance period. Actual performance exceeded the target performance for the performance period which resulted in an additional grant of 3,945 shares.

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.

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.

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.

Represents shares withheld by the issuer to satisfy applicable tax withholding obligations in connection with the vesting of 25,038 previously reported time-based restricted stock units, the remaining shares of which were issued and added to the reporting person's common stock holdings.

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.

Represents shares held by the issuer to satisfy applicable tax withholding obligations in connection with the vesting of 8,946 previously reported time-based restricted stock units, the remaining shares of which were issued and added to the reporting person's common stock holdings.

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.

Represents shares withheld by the issuer to satisfy applicable tax withholding obligations in connection with the vesting of 8,246 previously reported time-based restricted stock units, the remaining shares of which were issued and added to the reporting person's common stock holdings.

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.

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.

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.

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.

Represents shares withheld by the issuer to satisfy applicable tax withholding obligations in connection with the vesting of 2,585 previously reported time-based restricted stock units, the remaining shares of which were issued and added to the reporting person's common stock holdings.

Represents shares withheld by the issuer to satisfy applicable tax withholding obligations in connection with the vesting of 5,256 previously reported time-based restricted stock units, the remaining shares of which were issued and added to the reporting person's common stock holdings.