Mich. Comp. Laws § 450.1741

Sec. 741. At any time before the effective date of a certificate of merger or share exchange, the merger or share exchange may be abandoned, subject to any contractual rights, without further shareholder action, in accordance with the procedure set forth in the plan of merger or share exchange or, if none is set forth, in the manner determined by the board. If a certificate of merger or share exchange has been filed by a corporation, it shall file a certificate of abandonment within 10 days after the abandonment, but not later than the proposed effective day.