Rule 15.Amended and supplemental pleadings.

Last verified July 1, 2026

In one sentenceRule 15 lets a party amend a pleading once as a matter of course, requires leave of court or consent for later amendments, and lets an amendment relate back to the original filing date when it targets the same conduct or corrects a mistaken party.

Full Text of Rule 15

Text sizeJump to: (a) (b) (c) (d)

(a) Amendments before trial.

(1) Amending as a matter of course. A party may amend its pleading once as a matter of course:

(A) no later than 21 days after serving it if the pleading is one to which no responsive pleading is permitted; or

(B) no later than 21 days after a responsive pleading is served if the pleading is one to which a responsive pleading is required or, if a motion under Rule 12(b), (e), or (f) is served, on or before the date on which a response to the motion is due, whichever is earlier.

(2) Other amendments. In all other instances, a party may amend its pleading only with leave of court or with the written consent of all opposing parties who have appeared in the action. Leave to amend must be freely given when justice requires.

(3) Effect on pending motions. After the filing of a motion under Rule 12(b), (e), or (f), amending a pleading as a matter of course does not, by itself, make moot the motion as to the adequacy of the pleading’s allegations as revised in the amended pleading and does not relieve a party opposing the motion from filing a timely response.

(4) Proposed pleading as an exhibit. A party moving for leave to amend a pleading must attach a copy of the proposed amended pleading as an exhibit to the motion. The exhibit must show the respects in which the proposed pleading differs from the existing pleading by bracketing or striking through the text to be deleted and underlining the text to be added.

(5) Filing and response. If a motion for leave to amend is granted, the moving party must file and serve the amended pleading within 10 days after the entry of the order granting the motion, unless the court orders otherwise. If the pleading is one to which a responsive pleading is required, an opposing party must answer or otherwise respond to an amended pleading within the time remaining for response to the original pleading or within 10 days after the amended pleading is served, whichever is later, unless the court orders otherwise.

(b) Amendments during and after trial.

(1) Based on an objection at trial. If, at trial, a party objects that evidence is not within the issues raised in the pleadings, the court may permit the pleadings to be amended. The court should freely permit an amendment when doing so will aid in presenting the merits and the objecting party fails to satisfy the court that the evidence would unfairly prejudice that party’s claim or defense on the merits. The court may grant a continuance to enable the objecting party to respond to the evidence.

(2) For issues tried by consent. When an issue not raised by the pleadings is tried by the parties’ express or implied consent, it must be treated in all respects as if it had been raised in the pleadings. A party may move—at any time, even after judgment—to amend the pleadings to conform to the evidence and to raise an unpleaded issue. But failure to amend does not affect the result of the trial of that issue.

(1) Amendment adding claim or defense. An amendment relates back to the date of the original pleading if the amendment asserts a claim or defense that arose out of the conduct, transaction, or occurrence set forth, or attempted to be set forth, in the original pleading.

(2) Amendment changing party. An amendment changing the party against whom a claim is asserted relates back if:

(A) Rule 15(c)(1) is satisfied; and

(B) within the applicable limitations period—plus the period provided in Rule 4(i) for the service of the summons and complaint—the party to be brought in by amendment:

(i) has received such notice of the institution of the action that it will not be prejudiced in maintaining a defense on the merits; and

(ii) knew or should have known that, but for a mistake concerning the identity of the proper party, the action would have been brought against the party.

(3) Service. Service of process in compliance with Rule 4.1(h), (i), or (j) satisfies Rule 15(c)(2)(B)(i) and (ii) with respect to the state, county, or municipal corporation—or any agency or officer of those entities—to be brought into the action as a defendant.

(d) Supplemental pleadings. On motion and reasonable notice, the court may permit a party to file a supplemental pleading setting forth any transaction, occurrence, or event that happened after the date of the pleading to be supplemented. A court may permit supplementation even though the original pleading is defective in stating a claim for relief or defense. The court may order the opposing party to answer or otherwise respond to the supplemental pleading within a specified time.

End

Amendment History

Promulgated by R-16-0010, effective January 1, 2017.

Plain-English Summary

A party can amend a pleading once without needing permission — within 21 days of serving it if no response is allowed, or within 21 days of a response (or a Rule 12 motion) if one is required. Beyond that window, amendment needs either the court's leave or every appearing opposing party's written consent, and courts are directed to give leave freely when justice calls for it. A motion for leave to amend must attach the proposed amended pleading, marked up to show what's being added or deleted, and if the motion is granted, the amended pleading must generally be filed within 10 days.

During or after trial, a court may allow the pleadings to be amended to match evidence a party objected to as outside the pleadings, and should do so freely unless the objecting party shows unfair prejudice; when an issue outside the pleadings is tried by the parties' consent, it's treated as if it had been pleaded all along, whether or not anyone later moves to amend.

An amendment relates back to the date of the original pleading when it grows out of the same conduct, transaction, or occurrence already described there. Relation back for a change in parties works the same way, but only if the new party received enough notice of the action, within the time allowed for service, that it won't be prejudiced in defending on the merits, and knew or should have known the suit would have targeted it but for a mistake about identity.

Separately, a court may allow a supplemental pleading describing something that happened after the original pleading was filed, even if that original pleading had its own defects, and may set a deadline for the opposing party to respond to it.

Frequently Asked Questions

Can a party amend a pleading without asking the court's permission?

Yes, once, within 21 days of serving it, or within 21 days of a required response — or, if a Rule 12(b), (e), or (f) motion is served, by the date a response to that motion is due, whichever comes first.

What must accompany a motion for leave to amend a pleading?

A copy of the proposed amended pleading showing, through bracketing, striking, or underlining, exactly what's being changed.

When does an amendment "relate back" to the date of the original pleading?

When it arises from the same conduct, transaction, or occurrence already described in the original pleading.

Can a new party be added by amendment after the statute of limitations has run?

Sometimes — if the new party had timely notice of the action and knew or should have known it would have been sued but for a mistake about identity.

Source & verification. The rule text and History are reproduced verbatim from the official Arizona Rules of Civil Procedure (Ariz. R. Civ. P. 15). Prescribed by the Supreme Court of Arizona (Ariz. Const. art. 6, § 5). The plain-English summary is original and written by us. Last verified July 1, 2026. · Official source

Also known as: amending a complaintrelation backsupplemental pleadingleave to amend