Michigan Form MI-1040H, Schedule of Apportionment
Business income from business activity that is taxable both within and outside Michigan is apportioned to Michigan is apportioned to MI for individual income tax (IIT) purposes using this form. this form is also used to apportion business income for fiduciary and composite filers.
Use the factors of the business entity having the multistate activity. A separate MI-1040H must be completed for each taxable entity or sole proprietorship with multistate business activity. The Michigan income tax statute uses the standards prescribed by federal Public Law (PL) 86-272 to determine if a taxpayer is taxable in another state.
A taxpayer's income is taxable in another state if:
- In that state the taxpayer is subject to a net income tax; a franchise tax measured by net income; a franchise tax for the privilege of doing business; a corporate stock tax, or
- That state has jurisdiction to subject the taxpayer to a net income tax regardless of whether the state does or does not.
http://www.michigan.gov/documents/taxes/MI-1040H_711891_7.pdf