Company: ISBA
Filing Date: 2025-05-08
Form Type: 8-A12B
Source: 0000842517-25-000102
Chunk: 0

Company: ISABELLA BANK CORP
Filing Date: 2025-05-08
Form: 8-A12B
Chunk 0
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### UNITED STATES

### SECURITIES AND EXCHANGE COMMISSION

#### Washington, D.C. 20549

#### FORM 8-A

### FOR REGISTRATION OF CERTAIN CLASSES OF SECURITIES

#### PURSUANT TO SECTION 12(b) OR (g) OF

#### THE SECURITIES EXCHANGE ACT OF 1934

### ISABELLA BANK CORPORATION
<div align='center'>(Exact name of registrant as specified in its charter)</div>

| Michigan                     |     | 38-2830092         |
| (State or other jurisdiction 
 of incorporation)            |     | -IRS Employer      
 Identification No. |

|                                          |     | 401 North Main Street | Mt. Pleasant |     | Michigan |     | 48858-1649 |
| (Address of principal executive offices) |     |                       |              |     |          |     | -Zip Code  |

<div align='center'>Securities registered pursuant to Section 12(b) of the Act:</div>

| Common stock, no par value per share |     | The Nasdaq Stock Market LLC                                   |
| Title of each class to be registered |     | Name of each exchange on which each class is to be registered |

If this form relates to the registration of a class of securities pursuant to Section 12(b) of the Exchange Act and is effective pursuant to General Instruction A.(c) or (e), check the following box. ☒

If this form relates to the registration of a class of securities pursuant to Section 12(g) of the Exchange Act and is effective pursuant to General Instruction A.(d) or (e), check the following box. ☐

If this form relates to the registration of a class of securities concurrently with a Regulation A offering, check the following box. ☐

<div align='center'>Securities Act registration statement or Regulation A offering statement file number to which this form relates (if applicable): Not applicable

Securities to be registered pursuant to Section 12(g) of the Act: None</div>

| (Title of class) |

| (Title of class) |

## Item 1. Description of Registrant’s Securities to be Registered.

#### General
Isabella Bank Corporation (“ISBA”) is incorporated in the State of Michigan. The rights of our shareholders are generally governed by Michigan law, our Articles of Incorporation (as amended, the “Articles of Incorporation”) and our Bylaws (as amended, the “Bylaws”). The