Mich. Comp. Laws § 141.36

Sec. 6. The board of sinking fund commissioners shall from time to time, but at least annually, and whenever requested by the board of supervisors, make report of the condition of the sinking fund, which report shall be made to the board of supervisors and then referred to and filed with the county clerk and be recorded by him. It shall recommend to the board of supervisors the sum of money that in its judgment should be raised by direct taxation for the benefit of the sinking fund.