Michigan Compiled Laws, Chapter 141. Municipal Financing § 141.2705

Sec. 705. (1) Debt retirement funds, except in the case of a common debt retirement fund maintained by a school district pursuant to section 1223 of the revised school code, 1976 PA 451, MCL 380.1223, shall be accounted for separately and, debt retirement funds, except as provided in section 701(5),  1 shall be used only to retire the municipal securities of the municipality for which the debt retirement fund was created. Debt retirement funds created for the following categories of debt evidenced by a municipal security may be pooled or combined for deposit or investment purposes only with other debt retirement funds created for the same category of debt evidenced by a municipal security:

(2) When any municipality completes the retirement of a debt evidenced by a municipal security or accumulates sufficient funds in the debt retirement fund for the retirement of the debts evidenced by a municipal security, the governing body of the municipality shall certify that the debt evidenced by a municipal security is retired or that the debt retirement fund is of sufficient amount to retire the debt evidenced by a municipal security to the county treasurer of the county in which the municipality is located, and the county treasurer shall no longer be required to recognize a levy for the debt or municipal security issue.