Wis. Stat. § 767.895: Motion to reopen judgment based on statement acknowledging paternity.

A judgment which adjudicates a person to be the father of a child and which was based upon a statement acknowledging paternity that was signed and filed before April 1, 1998, may, if no trial was conducted, be reopened under any of the following circumstances:

(1) At any time upon motion or petition for good cause shown.

(2) Upon a motion under s. 806.07.

(3) Within one year after entry of the judgment upon motion or petition.