Mich. Comp. Laws § 400.68a
The county department furnishing general relief, including medical care, hospitalization or infirmary care to any poor person at the expense of another county in this state, shall present to the department of social welfare of the county liable for the aid and infirmary care, from time to time as the case might be, a sworn, itemized statement of the expense which shall be allowed and paid by the department of social welfare of the county liable therefor, within 60 days after being presented. No item of the itemized statement of expense shall be a proper and collectible charge against the county which has been determined to be or has agreed to be liable therefor unless submitted within 180 days from the end of the month during which services covered by the item were rendered. In the case of an item, the exact amount of which the county department furnishing care is unable to determine during the 180 days period or prior thereto, notice of the existence of such an item of undetermined amount shall be given the county liable during the 180 days whereupon the county furnishing care shall have an additional 180 days in which to include the amount of the item in an itemized statement.
MCL 400.68a