There are several provisions in the MBT that persons believe may be unconstitutional. Specifically, the nexus standard, the unitary and apportionment provisions and the Michigan only credits have drawn attention and may result in litigation. To protect the MBT in the event of an unfavorable ruling that may have the effect of voiding the MBT, severability section was put into the act. The severability section provides that if any provision of the MBT is determined to be unconstitutional, it shall be severed and shall not be in effect for any other tax year for which the final order shall apply, and the remaining provisions of this MBT shall remain in effect.

If a final order of a court of competent jurisdiction for which all rights of appeal have been exhausted or have expired determines that any provision of the MBTA that provides a deduction, credit, or exemption with respect to employment, persons, services, investment, or any other activity that is limited only to Michigan is unconstitutional or applies to employment, persons, services, investment, or any other activity outside of Michigan, that credit, deduction, or exemption shall be severed and shall not be in effect for any other tax year for which the final order shall apply, and the remaining provisions of this act shall remain in effect. [MCL 208.1519]