The MBTA does not provide for "throw back sales." A "throw back sale" describes a situation in which the income or activity from a Michigan taxpayer's sale of tangible personal property to an out-of-state purchaser is not taxable in the state of the purchaser. The sale would then be "thrown back" to Michigan by inclusion in the sales apportionment factor' s numerator, and increase the portion of the tax base subject to the Michigan Business Tax.

Sales to destinations outside Michigan need not be included in the MBT sales factor numerator regardless of whether nexus exists or tax is paid in the destination jurisdiction. However, if the taxpayer does not have nexus in at least one other state, they cannot apportion their tax base, and all business income, modified gross receipts and net capital tax bases are fully allocated to Michigan. The direct premiums tax base for insurance companies is not subject to apportionment.