For a unitary group with business activities within and without Michigan, the tax base is apportioned to this state by multiplying it by the sales factor. MCL 206.661. The sales factor is Michigan sales divided by everywhere sales. MCL 206.663(1). Sales includes sales in this state of every person included in the unitary business group without regard to whether the person has nexus in this state. Sales between persons included in a unitary business group must be eliminated in calculating the sales factor. MCL 206.663(2).

The tax base of a unitary business group comprised of financial institutions whose business activities are subject to tax within and without Michigan are apportioned by multiplying the tax base by the gross business factor.