Mich. Comp. Laws § 400.66m: Invoices for reimbursement.

Sec. 66m.

In a county operating a patient care management system, health care providers shall submit invoices for reimbursement to the office established by the county under section 66k in a manner prescribed by the office. An invoice that is approved for payment by an office shall be paid not later than 60 days after the invoice is received by the office, unless a different time period is established by contract between a health care provider and the county as part of a patient care management system.