Wis. Stat. § 846.02: Foreclosure; defendant may have assignment of mortgage.

(1) In a mortgage foreclosure action, any defendant may upon payment to the plaintiff or the plaintiff’s attorney, of the amount then owing thereon for principal, together with interest and all costs up to such time, demand the assignment of such mortgage to the defendant. The plaintiff shall upon such demand and a tender of the amount owing for principal, interest and costs, assign the mortgage to such defendant and the plaintiff shall be barred from further prosecuting such action. If dispute shall arise over the amount due for costs, application to fix the costs accrued shall be made to the court in which such action is pending.

(2) If such demand and tender is made after judgment, the plaintiff or the plaintiff’s assignee shall assign such judgment to such defendant.