Company: OSBC
Filing Date: 2025-05-08
Form Type: 424B3
Source: 0001104659-25-046065
Chunk: 133

Company: OLD SECOND BANCORP INC
Filing Date: 2025-05-08
Form: 424B3
Chunk 133
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 eliminate historical Bancorp Financial common stock and to record the issuance of 8.1 million shares of newly issued Old Second common stock, at $1.00 par value per share, at a historical cost of $133.8 million, to holders of Bancorp Financial common stock, based on 3,139,058 shares of Bancorp Financial common stock outstanding on March 14, 2025, multiplied by the exchange ratio of 2.5814 shares of Old Second common stock for each share of Bancorp Financial common stock.

(M)

Adjustment to eliminate Bancorp Financial additional paid-in capital of $47.3 million and to reflect the issuance of Old Second common stock in excess of par value of $125.7 million.

(N)

Adjustment to eliminate the retained earnings and the accumulated other comprehensive income of Bancorp Financial.

(O)

Adjustment to reflect the after-tax impact to retained earnings of the day two provision for credit losses, as well as the estimated accruals for merger-related professional, legal and other contractually obligated merger expenses expected to be incurred.

(P)

Adjustments to record estimated accretion of discounts on loans associated with the merger.

(Q)

Adjustments to record estimated amortization premium on interest-bearing deposits associated with the merger.

(R)

Adjustments to record estimated merger related expenses.

(S)

Adjustments to record estimated amortization of core deposit premium associated with the merger.

(T)

Adjustments due to the tax effect of the day two provision for credit losses, as well as the estimated accrual for merger related professional, legal and other contractually obligated merger expenses expected to be incurred, calculated at a 21% tax rate.

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TABLE OF CONTENTS

### BANCORP FINANCIAL STOCKHOLDERS’ APPRAISAL RIGHTS
The following is a summary of the material statutory procedures for stockholders of Bancorp Financial to exercise appraisal rights under Section 262 of the DGCL in connection with the proposed merger. This summary is not exhaustive and is qualified in its entirety by reference to Section 262 of the DGCL, the full text of which is attached as Annex C to this proxy statement/prospectus. Stockholders are encouraged to read Section 262 carefully and consult with legal counsel before attempting to exercise appraisal rights, as failure to strictly comply with the statutory procedures may result in a loss of such rights.

#### General
If the merger is completed, holders of Bancorp Financial common stock who (i) do not vote in favor of