Rule 15.Amended and Supplemental Pleadings

Last amended December 1, 2023 · Last verified June 30, 2026

In one sentenceRule 15 governs amending pleadings — once as a matter of course within 21 days, and otherwise only with the opposing party’s consent or the court’s leave, which should be freely given — and sets when an amendment relates back to the original filing date.

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 no later than:

(A) 21 days after serving it, or

(B) if the pleading is one to which a responsive pleading is required, 21 days after service of a responsive pleading or 21 days after service of a motion under Rule 12(b), (e), or (f), whichever is earlier.

(2) Other Amendments. In all other cases, a party may amend its pleading only with the opposing party's written consent or the court's leave. The court should freely give leave when justice so requires.

(3) Time to Respond. Unless the court orders otherwise, any required response to an amended pleading must be made within the time remaining to respond to the original pleading or within 14 days after service of the amended pleading, whichever is later.

(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 prejudice that party's action or defense on the merits. The court may grant a continuance to enable the objecting party to meet 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 raised in the pleadings. A party may move—at any time, even after judgment—to amend the pleadings to conform them 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) When an Amendment Relates Back. An amendment to a pleading relates back to the date of the original pleading when:

(A) the law that provides the applicable statute of limitations allows relation back;

(B) the amendment asserts a claim or defense that arose out of the conduct, transaction, or occurrence set out—or attempted to be set out—in the original pleading; or

(C) the amendment changes the party or the naming of the party against whom a claim is asserted, if Rule 15(c)(1)(B) is satisfied and if, within the period provided by Rule 4(m) for serving the summons and complaint, the party to be brought in by amendment:

(i) received such notice of the action that it will not be prejudiced in defending on the merits; and

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

(2) Notice to the United States. When the United States or a United States officer or agency is added as a defendant by amendment, the notice requirements of Rule 15(c)(1)(C)(i) and (ii) are satisfied if, during the stated period, process was delivered or mailed to the United States attorney or the United States attorney's designee, to the Attorney General of the United States, or to the officer or agency.

(d) Supplemental Pleadings. On motion and reasonable notice, the court may, on just terms, permit a party to serve a supplemental pleading setting out any transaction, occurrence, or event that happened after the date of the pleading to be supplemented. The court may permit supplementation even though the original pleading is defective in stating a claim or defense. The court may order that the opposing party plead to the supplemental pleading within a specified time.

End

Amendment History

(Amended January 21, 1963, effective July 1, 1963; February 28, 1966, effective July 1, 1966; March 2, 1987, effective August 1, 1987; April 30, 1991, effective December 1, 1991; amended by Pub.L. 102-198, § 11, December 9, 1991, 105 Stat. 1626; amended April 22, 1993, effective December 1, 1993; April 30, 2007, effective December 1, 2007; March 26, 2009, effective December 1, 2009; April 24, 2023, effective December 1, 2023.)

Plain-English Summary

Rule 15 keeps pleadings flexible. A party may amend once as a matter of course within 21 days after serving the pleading, or within 21 days after a responsive pleading or a Rule 12 motion. After that, a party needs the opposing party’s written consent or the court’s leave — and the court should give leave freely when justice requires.

The rule also lets pleadings be amended during and after trial to conform to the evidence, and it governs relation back: when an amendment asserts a claim or defense arising out of the same conduct, transaction, or occurrence set out in the original pleading, the amendment is treated as filed on the original date. Relation back can be decisive when the statute of limitations has run. Supplemental pleadings cover events that happen after the original pleading.

Frequently Asked Questions

How do you amend a complaint in federal court?

Once as a matter of course within 21 days; after that, only with the other party’s written consent or the court’s leave, which should be freely given when justice requires (Rule 15(a)).

What is “relation back” of an amendment?

When an amendment arises from the same conduct, transaction, or occurrence as the original pleading, it is treated as filed on the original date — which can preserve a claim against a limitations bar (Rule 15(c)).

Source & verification. The rule text and amendment history are reproduced verbatim from the official Federal Rules of Civil Procedure (Fed. R. Civ. P. 15), a public-domain work of the U.S. Government. Prescribed by the United States Supreme Court under the Rules Enabling Act. The plain-English summary is original and written by us. Last verified June 30, 2026. · Official source

Also known as: FRCP 15Fed. R. Civ. P. 15amended pleadingsleave to amendrelation backsupplemental pleadings