Company: ISBA
Filing Date: 2025-03-25
Form Type: DEF 14A
Source: 0000842517-25-000071
Chunk: 0

Company: ISABELLA BANK CORP
Filing Date: 2025-03-25
Form: DEF 14A
Chunk 0
---
### UNITED STATES

### SECURITIES AND EXCHANGE COMMISSION

#### Washington, D.C. 20549

#### SCHEDULE 14A

#### Proxy Statement Pursuant to Section 14(a) of the

#### Securities Exchange Act of 1934
<div align='center'>(Amendment No. )</div>

Filed by the Registrant ý Filed by a Party other than the Registrant ¨

Check the appropriate box:

| ¨ |     | Preliminary Proxy Statement                                                     |
| ¨ |     | Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) |
| ý |     | Definitive Proxy Statement                                                      |
| ¨ |     | Definitive Additional Materials                                                 |
| ¨ |     | Soliciting Material Under §240.14a-12                                           |

<div align='center'>ISABELLA BANK CORPORATION</div>

| (Name of Registrant as Specified In Its Charter)                         |     |                                                                                                                                                                                                                                                                                     |     |                                                                                                                                                                                                   |
| (Name of Person(s) Filing Proxy Statement, if other than the Registrant) |     |                                                                                                                                                                                                                                                                                     |     |                                                                                                                                                                                                   |
| Payment of Filing Fee (Check the appropriate box):                       |     |                                                                                                                                                                                                                                                                                     |     |                                                                                                                                                                                                   |
| ý                                                                        |     | No fee required.                                                                                                                                                                                                                                                                    |     |                                                                                                                                                                                                   |
| ¨                                                                        |     | Fee computed on table below per Exchange Act Rules 14a-6(i)(1) and 0-11.                                                                                                                                                                                                            |     |                                                                                                                                                                                                   |
|                                                                          |     | 1)                                                                                                                                                                                                                                                                                  |     | Title of each class of securities to which transaction applies:                                                                                                                                   |
|                                                                          |     | 2)                                                                                                                                                                                                                                                                                  |     | Aggregate number of securities to which transaction applies:                                                                                                                                      |
|                                                                          |     | 3)                                                                                                                                                                                                                                                                                  |     | Per unit price or other underlying value of transaction computed pursuant to Exchange Act Rule 0-11 (set forth the amount on which the filing fee is calculated and state how it was determined): |
|                                                                          |     | 4)                                                                                                                                                                                                                                                                                  |     | Proposed maximum aggregate value of transaction:                                                                                                                                                  |
|                                                                          |     | 5)                                                                                                                                                                                                                                                                                  |     | Total fee paid:                                                                                                                                                                                   |
| ¨                                                                        |     | Fee paid previously with preliminary materials.                                                                                                                                                                                                                                     |     |                                                                                                                                                                                                   |
| ¨                                                                        |