Mich. Comp. Laws § 208.1301

Sec. 301. (1) Except as otherwise provided in this act, each tax base established under this act shall be apportioned in accordance with this chapter. (2) Each tax base of a taxpayer whose business activities are confined solely to this state shall be allocated to this state. Each tax base of a taxpayer whose business activities are subject to tax both within and outside of this state shall be apportioned to this state by multiplying each tax base by the sales factor calculated under section 303. (3) A taxpayer whose business activities are subject to tax both within and outside of this state is subject to tax in another state in either of the following circumstances: (a) The taxpayer is subject to a business privilege tax, a net income tax, a franchise tax measured by net income, a franchise tax for the privilege of doing business, or a corporate stock tax or a tax of the type imposed under this act in that state. (b) That state has jurisdiction to subject the taxpayer to 1 or more of the taxes listed in subdivision (a) regardless of whether that state does or does not subject the taxpayer to that tax.