Company: OSBC
Filing Date: 2025-04-23
Form Type: S-4
Source: 0001104659-25-037832
Chunk: 239

Company: OLD SECOND BANCORP INC
Filing Date: 2025-04-23
Form: S-4
Chunk 239
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 reflects the potential dilution that could occur if stock-based awards from the Company’s Incentive Compensation Plan were exercised or issued. Earnings per common share have been computed as follows:

| ​                                                                             
 ​                                                                             | ​ 
 ​ | ​ 
 ​ | For the years ended December 31, 
 2024                             |   |           |   | ​ | ​ | 2023 |   |           |   | ​ 
 ​ |
|:------------------------------------------------------------------------------|:--|:--|:---------------------------------|:--|----------:|:--|:--|:--|:-----|:--|----------:|:--|:--|
| Net income available to common stockholders                                   | ​ | ​ | ​                                | $ | 5,083,769 | ​ | ​ | ​ | ​    | $ | 5,790,183 | ​ | ​ |
| Weighted average number of common shares outstanding for basic EPS            | ​ | ​ | ​                                | ​ | 2,793,912 | ​ | ​ | ​ | ​    | ​ | 2,770,059 | ​ | ​ |
| Dilutive effect of stock based awards                                         | ​ | ​ | ​                                | ​ |   187,669 | ​ | ​ | ​ | ​    | ​ |   176,568 | ​ | ​ |
| Weighted average number of common and potential common shares for diluted EPS | ​ | ​ | ​                                | ​ | 2,981,581 | ​ | ​ | ​ | ​    | ​ | 2,946,627 | ​ | ​ |
| Basic earnings per common share                                               | ​ | ​ | ​                                | $ |      1.82 | ​ | ​ | ​ | ​    | $ |      2.09 | ​ | ​ |
| Diluted earnings per common share                                             | ​ | ​ | ​                                | $ |      1.71 | ​ | ​ | ​ | ​    | $ |      1.97 | ​ | ​ |

There were no anti-dilutive shares in the 2024 or 2023 computations.

F-36

TABLE OF CONTENTS

#### Annex A
Execution Version

### AGREEMENT AND PLAN OF MERGER
<div align='center'>by and between</div>

#### OLD SECOND BANCORP, INC.
<div align='center'>and</div>

#### BANCORP FINANCIAL, INC.
<div align='center