Wis. Stat. § 769.506: Contest by obligor.

(1) An obligor may contest the validity or enforcement of an income-withholding order issued in another state and received directly by an employer in this state by registering the order in a tribunal of this state and filing a contest to that order as provided in subch. VI, or otherwise contesting the order in the same manner as if the order had been issued by a tribunal of this state. Section 769.604 applies to the contest.

(2) The obligor shall give notice of the contest to all of the following:

(a) A support enforcement agency providing services to the obligee.

(b) Each employer that has directly received an income-withholding order.

(c) Except as provided in par. (d), the person designated to receive payments in the income-withholding order.

(d) If no person is designated to receive payments in the income-withholding order, the obligee.