Company: OSBC
Filing Date: 2025-04-23
Form Type: S-4
Source: 0001104659-25-037832
Chunk: 175

Company: OLD SECOND BANCORP INC
Filing Date: 2025-04-23
Form: S-4
Chunk 175
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 constitute an admission that the identified individuals act as, or constitute, a group.

(12)

Includes the following individuals: William Pacella, Rosemary Pacella, Anthony Pacella and Michael Pacella. The disclosure of this group ownership information does not constitute an admission that the identified individuals act as, or constitute, a group.

(13)

Includes the following individuals: Michael Spaniak and George Spaniak, Jr. The disclosure of this group ownership information does not constitute an admission that the identified individuals act as, or constitute, a group.

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### EXPERTS
The consolidated financial statements of Old Second as of December 31, 2023 and 2024, and for each of the years in the three-year period ended December 31, 2024, and the effectiveness of internal control over financial reporting as of December 31, 2024 have been incorporated by reference herein and in the registration statement in reliance upon the reports of Plante & Moran, PLLC, an independent registered public accounting firm, incorporated by reference herein, and upon the authority of said firm as experts in accounting and auditing.

The consolidated financial statements of Bancorp Financial, Inc. as of December 31, 2023 and 2024, and for each of the years in the two-year period ended December 31, 2024, included herein have been audited by RSM US LLP, an independent auditor, as stated in their reports thereon and included in the registration statement of which this proxy statement/prospectus is a part in reliance upon such reports and upon the authority of such firm as experts in accounting and auditing.

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### LEGAL OPINIONS
The validity of the shares of Old Second common stock to be issued in the merger will be passed upon for Old Second by Nelson Mullins Riley & Scarborough LLP. Certain U.S. federal income tax consequences of the merger will be passed upon for Old Second by Nelson Mullins Riley & Scarborough LLP and for Bancorp Financial by Vedder Price P.C.

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### HOUSEHOLDING OF PROXY MATERIALS
The SEC’s rules permit companies and intermediaries (such as brokers) to deliver a single copy of this proxy statement/prospectus to multiple stockholders who share the same address, unless one or more of those stockholders has objected to householding. This practice