Not being a MI resident does not, in itself, mean that you're not subject to MI tax. You need to explain the circumstances of "michigan taxed my income," and which state is your resident state, for more specific advice.
This is the general rule: The income is work state (WS) source income since it was earned there. Resident States (RS) tax all their resident's income, regardless of where earned. You will file a non-resident tax return for the WS and report the WS income. You will file a full year resident return for the RS, reporting all your income. The RS will give you a credit, or partial credit for any tax paid to the WS.
If the WS & RS are reciprocal states, it works differently.
