Mich. Comp. Laws § 211.212

Sec. 12. Tax levies to be in rates. In order that the maximum tax rates ordered by the board and tax levies pursuant thereto may not be invalidated by any process of determination or review of assessments subsequent to the allocation of the net limitation tax rate, all tax levies shall hereafter be made by prescribing the rate of taxes and the sums of money to be raised thereby, which shall be imposed upon property. No such levy shall be a rate in excess of the maximum tax rate ordered by the board or by the state tax commission in case of appeal: Provided, That nothing in this act shall be construed to limit or restrict the power of the state or local units to make tax levies separately in excess of such maximum tax rates for the purpose of payment of interest and principal on obligations incurred prior to December eighth, 1932.