Mich. Comp. Laws § 141.425: Local units; audits.

Sec. 5.

A local unit having a population of less than 4,000 shall obtain an audit of its financial records, accounts, and procedures not less frequently than biennially. However, if any audit under this subsection discloses a material deviation by the local unit from generally accepted accounting practices or from applicable rules and regulations of a state department or agency or discloses any fiscal irregularity, defalcation, misfeasance, nonfeasance, or malfeasance, the department of treasury may require an audit to be conducted in the next year.

A local unit having a population of 4,000 or more shall obtain an annual audit of its financial records, accounts, and procedures.