Amended and supplemental pleadings
Wis. Stat. § 802.09
in effect(1) Amendments. A party may amend the party’s pleading once as a matter of course at any time within 6 months after the summons and complaint are filed or within the time set in a scheduling order under s. 802.10. Otherwise a party may amend the pleading only by leave of court or by written consent of the adverse party; and leave shall be freely given at any stage of the action when justice so requires. A party shall plead in response to an amended pleading within 20 days after service of the amended pleading unless: a) the court otherwise orders; or b) no responsive pleading is required or permitted under s. 802.01 (1). If a defendant in the action is an insurance company, if any cause of action raised in the original pleading, cross-claim, or counterclaim is founded in tort, or if the party pleading in response is the state or an officer, agent, employee, or agency of the state, the 20-day time period under this subsection is increased to 45 days.
(2) Amendments to conform to the evidence. If issues not raised by the pleadings are tried by express or implied consent of the parties, they shall be treated in all respects as if they had been raised in the pleadings. Such amendment of the pleadings as may be necessary to cause them to conform to the evidence and to raise these issues may be made upon motion of any party at any time, even after judgment; but failure to so amend does not affect the result of the trial of these issues. If evidence is objected to at the trial on the ground that it is not within the issues made by the pleadings, the court may allow the pleadings to be amended and shall do so freely when the presentation of the merits of the action will be subserved thereby and the objecting party fails to satisfy the court that the admission of such evidence would prejudice such party in maintaining the action or defense upon the merits. The court may grant a continuance to enable the objecting party to meet such evidence.
(3) Relation back of amendments. If the claim asserted in the amended pleading arose out of the transaction, occurrence, or event set forth or attempted to be set forth in the original pleading, the amendment relates back to the date of the filing of the original pleading. An amendment changing the party against whom a claim is asserted relates back if the foregoing provision is satisfied and, within the period provided by law for commencing the action against such party, the party to be brought in by amendment has received such notice of the institution of the action that he or she will not be prejudiced in maintaining a defense on the merits, and knew or should have known that, but for a mistake concerning the identity of the proper party, the action would have been brought against such party.
(4) Supplemental pleadings. Upon motion of a party the court may, upon such terms as are just, permit the party to serve a supplemental pleading setting forth transactions or occurrences or events which have happened since the date of the pleading sought to be supplemented. Permission may be granted even though the original pleading is defective in its statement of a claim for relief or defense. If the court deems it advisable that the adverse party plead to the supplemental pleading, it shall so order, specifying the time therefor.
(5) Telephone hearings. Oral argument permitted on motions under this section may be heard as prescribed in s. 807.13 (1).
Source: WI Statutes (Official Site)URL: https://docs.legis.wisconsin.gov/document/statutes/802.09Fetched: 10/7/2026