Mich. Comp. Laws § 205.54z

Sec. 4z. (1) For taxes levied after December 31, 1990 and before July 1, 1999, the tax levied under this act does not apply to a claimed exemption of tangible personal property used in the construction, alteration, repair, or improvement of the real estate or is affixed to and made a structural part of a building of a nonprofit hospital provided the following criteria have been met: (a) A nonprofit hospital is an entity described in section 4w(3)(a)(i). (b) A binding contract had been entered into for the construction, alteration, repair, or improvement of the real estate or the affixation to the building before July 1, 1999. (c) The claimed exemption was made in good faith. (2) The provisions of this section shall not be applied to affect any final decision of a court. (3) A claim for refund for an exemption under this section shall be filed not later than July 15, 1999. The approved refunds shall be paid without interest.