(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.
802.09.Amended and supplemental pleadings.
Ch. 802: Pleadings, Motions and Pretrial Practice · Last amended 2005 · Last verified July 15, 2026
In one sentenceSection 802.09 lets a party amend a pleading once as a matter of course within six months of filing or a scheduling order’s deadline, otherwise only with leave of court or the other side’s consent, and it covers amendments that conform to trial evidence, relation back to the original filing date, and supplemental pleadings for later events.
Full Text of Section 802.09
(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.
Official Notes
Judicial Council Committee’s Note, 1977: Sub. (1) has been amended to allow a party to amend pleadings once as a matter of course at any time within 6 months of the time the summons and complaint are filed or within a time established in a scheduling order under s. 802.10. The 6-month time period has been established as the previous procedure stating that a party is allowed to amend pleadings once as a matter of course at any time prior to the entry of a scheduling order is no longer applicable in most cases. The use of a scheduling order is now discretionary under s. 802.10. Sub. (1) also clarifies that leave of the court may be given at any stage of the action for amendment of pleadings when justice requires. Sub. (3) has been amended to adopt language consistent with revised s. 802.02 (1). See note following s. 802.02 (1). [Re Order effective July 1, 1978]
Judicial Council Note, 1988: Sub. (5) [created] allows oral arguments permitted on motions under this section to be heard by telephone conference. [Re Order effective Jan. 1, 1988]
Plain-English Summary
A party may amend its pleading once as a matter of course within six months after the summons and complaint were filed, or within a scheduling order’s deadline; after that, amendment requires leave of court, freely given when justice requires, or the other party’s written consent. A response to an amended pleading is generally due within 20 days, extended to 45 days for the same categories, insurers, tort claims, and the state, that get extended time elsewhere in this chapter, unless the court orders otherwise or no response is required.
If issues not raised in the pleadings are tried by the parties’ express or implied consent, section 802.09(2) treats them as if they had been pleaded all along, and the pleadings may be amended to match the evidence at any time, even after judgment, though failing to amend does not undo the result of trying those issues. If evidence is objected to as outside the pleadings, the court may allow amendment and should do so freely when it serves the merits and the objecting party cannot show real prejudice, granting a continuance if needed to let that party respond to the new evidence.
An amendment relates back to the original filing date if the claim in it arose from the same transaction, occurrence, or event as the original pleading. An amendment that changes the defendant relates back on the same condition, plus two more: the new party received enough notice of the case, within the time otherwise allowed to sue it, that it will not be prejudiced in defending on the merits, and it knew or should have known that, but for a mistake about identity, the action would have named it. Finally, a party may seek leave to serve a supplemental pleading covering events that happened after the original pleading, even if that original pleading was itself defective in stating a claim or defense, and the court can order the other side to respond to it.
Frequently Asked Questions
Can I amend my Wisconsin complaint without asking the court’s permission?
Yes, once as a matter of course within six months after the summons and complaint were filed, or within a scheduling order’s deadline; after that you need leave of court or the other party’s written consent.
Does an amended complaint keep the original filing date for statute-of-limitations purposes?
Yes, if the claim in the amendment arose from the same transaction, occurrence, or event as the original pleading, the amendment relates back to the original filing date.
Can I add a new defendant by amendment and have it relate back?
Yes, if the new party received enough notice of the case to avoid prejudice in defending on the merits, and knew or should have known the action would have named it but for a mistake about identity.
What happens if evidence comes in at trial on an issue I never pleaded?
If it is tried by the parties’ express or implied consent, section 802.09(2) treats it as though it had been raised in the pleadings, and the pleadings may be amended to match, even after judgment.
Can I add claims about events that happened after I filed my original pleading?
Yes, through a supplemental pleading permitted by the court, even if the original pleading was itself defective in stating a claim or defense.
Amendment History
History: Sup. Ct. Order, 67 Wis. 2d 585, 632 (1975); 1975 c. 218; Sup. Ct. Order, 82 Wis. 2d ix (1978); Sup. Ct. Order, 141 Wis. 2d xiii (1987); 1997 a. 187; 2001 a. 16; 2005 a. 442.
Source & verification. Section text and official notes are
reproduced verbatim from the Wisconsin Statutes, published by the
Wisconsin Legislature (Legislative Reference Bureau). Last verified July 15, 2026.
· Official source
Also known as: amending a complaint in wisconsinrelation back doctrine wisconsinsupplemental pleading wisconsinamend pleadings to conform to evidence wisconsinleave to amend wisconsin lawsuit