Michigan Compiled Laws, Chapter 141. Municipal Financing § 141.619

Sec. 19. The taxpayer may petition for and the administrator may grant approval of, or the administrator may require, the separate accounting method. If such method is petitioned for the administrator may require a statement, explaining the manner in which the apportionment will be made, in sufficient detail to determine whether the net profits attributable to the city will be apportioned with reasonable accuracy.