Corporate income tax: rate; pay ratio surcharge for certain corporations; provide for. Amends 1967 PA 281 (MCL 206.1 - 206.847) by adding sec. 684.

HB 4603 imposes a progressive surcharge on Michigan corporations required to disclose pay ratios under federal SEC rules (17 CFR 229.402(u)). The surcharge rate (0% to 50%) increases based on the corporation's disclosed CEO-to-median-worker pay ratio, starting October 1, 2025. It applies only to corporations already filing these SEC disclosures, with rates rising from 0% for ratios under 50:1 up to 50% for ratios of 500:1 or higher. The surcharge is calculated on the corporation’s state tax liability before credits and is administered under Michigan’s existing tax laws. It does not apply to corporations not required to file state tax returns.