(a) Amendments. A party may amend the party’s pleading once as a matter of course at any time before a responsive pleading is served or, if the pleading is one to which no responsive pleading is permitted and the action has not been placed upon the trial calendar, the party may so amend it at any time within 20 days after it is served. Otherwise, a party may amend the party’s pleading only by leave of court or by written consent of the adverse party; and leave shall be freely given when justice so requires. If a party moves to amend a pleading, a copy of the proposed amended pleading, denominated “proposed” and unsigned, shall be attached to the motion. If a motion to amend is granted, the moving party shall thereafter file the amended pleading and, pursuant to rule 5, serve a copy thereof on all other parties. A party shall plead in response to an amended pleading within the time remaining for response to the original pleading or within 10 days after service of the amended pleading, whichever period may be the longer, unless the court otherwise orders.
Rule 15.Amended and supplemental pleadings
Group 3: Pleadings and Motions · Last amended April 28, 2015 · Last verified July 13, 2026
In one sentenceRule 15 lets a party amend a pleading once without permission within set time limits, requires leave of court for later amendments that should be freely given, and allows an amendment to relate back to the original filing date even when it adds a new party.
Full Text of Rule 15
(b) Amendments to conform to the evidence. When 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 so to 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 him in maintaining his action or defense upon the merits. The court may grant a continuance to enable the objecting party to meet such evidence.
(c) Relation back of amendments. Whenever the claim or defense asserted in the amended pleading arose out of the conduct, transaction, or occurrence set forth or attempted to be set forth in the original pleading, the amendment relates back to the date 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 the original party, the party to be brought in by amendment (1) has received such notice of the institution of the action that the new party will not be prejudiced in maintaining her or his defense on the merits, and (2) 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 new party.
(d) Supplemental pleadings. Upon motion of a party the court may, upon reasonable notice and 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.
(e) Interlineations. No amendments shall be made to any pleading by erasing or adding words to the original on file, without first obtaining leave of court.
Amendment History
Adopted May 5, 1967, effective July 1, 1967; amended June 2, 2005, effective Sept. 1, 2005; amended, effective April 28, 2015.
Plain-English Summary
Rule 15 gives pleadings room to grow as a case develops. A party may amend a pleading once as a matter of course — no permission needed — any time before a responsive pleading is served, or, if no response is required and the case has not yet been calendared for trial, within 20 days after the pleading was served. Beyond that window, amendment requires either the other side's written consent or leave of court, and the rule instructs courts to grant that leave freely whenever justice calls for it. A party seeking leave must attach a proposed amended pleading to the motion, and once leave is granted, the amended pleading must be filed and served on every other party under Rule 5. The other side then has whichever is longer: the time remaining to respond to the original pleading, or 10 days after the amended one was served.
The rule also lets pleadings catch up to what happened at trial. When the parties try an issue that was not raised in the pleadings but do so knowingly or by implied consent, the court treats that issue as if it had been pleaded all along, and a motion to amend to match the evidence can be made even after judgment. If a party objects that evidence strays outside the pleadings, the court can allow an amendment anyway, and should do so freely, unless the objecting party shows real prejudice to its case — and even then a continuance can cure the problem.
Perhaps the highest-stakes feature of Rule 15 is relation back. An amendment that arises from the same conduct, transaction, or occurrence in the original pleading is treated as if filed on the original filing date — which can matter enormously once a statute of limitations has run. That protection extends to changing which party is being sued, but only if the new party received enough notice of the lawsuit within the time allowed for commencing the action that it will not be prejudiced in defending on the merits, and knew or should have known that but for a mistake about identity, the suit would have named it from the start. Separately, a party may seek to file a supplemental pleading describing events that happened after the original pleading, even if that original pleading had its own defects, and no pleading already on file may be altered by erasing or adding words without the court's leave.
Frequently Asked Questions
Can I amend my complaint without asking the court first?
Yes, once, as a matter of course — before the other side serves a responsive pleading, or, if no response is required and the case hasn't been set for trial, within 20 days after you served the original pleading. After that, you need either the other party's written consent or the court's permission.
What does 'relation back' mean and why does it matter?
An amendment that grows out of the same conduct, transaction, or occurrence as the original pleading is treated as if it had been filed on the original filing date. That can save a claim that would otherwise be barred by a statute of limitations that has since run.
Can I amend a pleading to add a new defendant after the statute of limitations has expired?
Only if the new party received enough notice of the lawsuit within the time allowed for commencing the action that it won't be prejudiced in defending on the merits, and it knew or should have known that but for a mistake about identity, it would have been named from the start.
What is a supplemental pleading, and how is it different from an amended pleading?
An amended pleading revises what was already alleged. A supplemental pleading adds transactions, occurrences, or events that happened after the original pleading was filed, and it may be permitted even if the original pleading had defects of its own.
Can I hand-write a change onto a pleading that's already been filed?
No. No amendment may be made by erasing or adding words to a pleading already on file without first getting the court's leave.
What happens if evidence at trial raises issues never mentioned in the pleadings?
If the parties try that issue by express or implied consent, it is treated as if it had been raised in the pleadings all along, and the pleadings may be amended to match — even after judgment — without affecting the trial's outcome.
Source & verification. Rule text and amendment history are
reproduced verbatim from the Washington Superior Court Civil Rules, adopted by the
Supreme Court of Washington. Last verified July 13, 2026. ·
Official source
Also known as: amend a complaint in Washingtonleave to amend a pleadingrelation back amendmentsupplemental pleadingamend pleading to add a defendant