Mich. Comp. Laws § 552.617

Sec. 17. For a friend of the court case, if the court orders a modification in support and an order of income withholding has been entered under this act, the office of the friend of the court shall give to a source of income to which notice of income withholding was sent under section 11 a notice of the modification by ordinary mail or by electronic means as agreed by the source of income and the office of the friend of the court. The amount assigned or withheld shall be changed to conform with the court ordered modification 7 days after receipt of the notice of modification.