I do not own a business. In 2024 I only worked in CA. However, a couple years back I worked in MI for a few days, which means for the following 4 years I have to file MI taxes as well due to RSU vesting. So my 2024 taxes were federal + CA + MI.

For details about why RSU vesting requires 4 years of MI taxes, see https://news.ycombinator.com/item?id=43676698