Company: OSBC
Filing Date: 2025-06-30
Form Type: 11-K
Source: 0000357173-25-000063
Chunk: 5

Company: OLD SECOND BANCORP INC
Filing Date: 2025-06-30
Form: 11-K
Chunk 5
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 schedule as follows:

| ​                        | ​ | ​                         | ​ |
| Years of vesting service |   | Nonforfeitable percentage |   |
| 0-1                      | ​ | 0%                        | ​ |
| 2                        | ​ | 20%                       | ​ |
| 3                        | ​ | 40%                       | ​ |
| 4                        | ​ | 60%                       | ​ |
| 5                        | ​ | 80%                       | ​ |
| 6                        | ​ | 100%                      | ​ |

Notes Receivable from Participants Participants may borrow from their accounts a maximum of the lesser of $50,000 or 50% of their vested account balance. Note terms generally range from one to five years, except in the case of a note for the purpose of acquiring a primary residence. The term of such note shall be determined by the Company. The notes are secured by the balance in the participant’s account and bear a reasonable rate of interest as determined by the Company. Principal and interest are paid ratably through semi-monthly payroll deductions. Plan Termination Although it has not expressed any intent to do so, the Company has the right under the Plan to discontinue its contributions at any time and to terminate the Plan subject to provisions of ERISA. Upon Plan termination, all participants become fully vested in their account balances. 2.Summary of Significant Accounting Policies The following is a summary of significant accounting policies followed by the Plan. Basis of Accounting The financial statements of the Plan are prepared on the accrual basis of accounting. Use of Estimates The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts included in the financial statements. Actual results could differ from those estimates.

8

#### Investment Valuation and Income Recognition
The Plan’s investments are reported at fair value. See Note 4 for additional information. Purchases and sales of securities are recorded on a trade date basis. Interest income is recorded on the accrual basis. Dividend income is recorded on the ex-dividend date.

#### Notes Receivable from Participants
Notes receivable from participants are recorded at their unpaid principal balances plus any accrued interest. Notes receivable from participants are written off when deemed uncollectible.

#### Payment of Benefits
Benefits are recorded when paid.

#### Administrative Expenses
Certain administrative expenses of the Plan are paid by the Company. The Plan allows administrative expenses to be paid by any forfeitures available; there were no forfeitures