Exhibit 99.1 Isabella Bank Corporation Reports Fourth Quarter 2024 Results MT. PLEASANT, MICHIGAN — January 30, 2025 — Isabella Bank Corporation (OTCQX: ISBA) (the "Company" or "we") reported fourth quarter 2024 net income of $4.0 million, or$0.54 per diluted share, an increase compared to $3.8 million, or$0.51 per diluted share in the same quarter of 2023. The non-GAAP measure of core earnings in the fourth quarter 2024 totaled $3.9 million, or$0.52 per diluted share, an increase compared to $3.8 millio ...