Mich. Comp. Laws § 211.25a
An assessing officer, with the approval of the governing body of the city or township, may establish a real estate index number system for listing real estate for purposes of assessment and collection of taxes, in addition to, or in lieu of, the method of listing by legal description provided in this act. The system shall describe real estate by county, township, section, block and parcel or lot. The numbering system shall be approved by the state tax commission. The assessing officer shall establish and maintain cross indexes of numbers assigned under the system with the complete legal description of the real estate to which such numbers relate. The assessing officer shall assign individual index numbers and the assessment rolls, tax rolls and tax statements shall carry the index numbers and not the legal descriptions, except that both the legal description and the index number shall be shown on the tax statements for the first year after this section is effective. Indexes established hereunder shall be open to public inspection.
MCL 211.25a