Mich. Comp. Laws § 550.930

Sec. 30. (1) A TPA may only provide administrative services pursuant to a written service contract. For the duration of the service contract, a TPA shall maintain at its principal administrative office the TPA's books and records of all transactions under the service contract in accordance with generally accepted accounting principles or as required by ERISA. (2) A TPA and a manager are a fiduciary when collecting, expending, and maintaining money for the payment of claims pursuant to the service contract.