Current through June 1, 2026 · Last verified July 10, 2026
In one sentenceRule 13 requires a party to raise any counterclaim arising from the same transaction as the opposing claim or lose it, allows unrelated counterclaims and cross-claims against a coparty, and lets a court add parties, order separate trials, and revive an omitted counterclaim by amendment.
(a)Compulsory Counterclaims. A pleading shall state as a counterclaim any claim which at the time of filing the pleading the pleader has against any opposing party, if it arises out of the transaction or occurrence that is the subject matter of the opposing party's claim and does not require for its adjudication the presence of third parties of whom the court cannot acquire jurisdiction. But the pleader need not state the claim if:
(1)At the time the action was commenced the claim was the subject of another pending action, or
(2)The opposing party brought suit upon his claim by attachment or other process by which the court did not acquire jurisdiction to render a personal judgment on that claim, and the pleader is not stating any counterclaim under this Rule 13.
(b)Permissive Counterclaim. A pleading may state as a counterclaim any claim against an opposing party not arising out of the transaction or occurrence that is the subject matter of the opposing party's claim.
(c)Counterclaim Exceeding Opposing Claim. A counterclaim may or may not diminish or defeat the recovery sought by the opposing party. It may claim relief exceeding in amount or different in kind from that sought in the pleading of the opposing party.
(e)Counterclaim Maturing or Acquired After Pleading. A claim which either matured or was acquired by the pleader after serving his pleading may, with the permission of the court, be presented as a counterclaim by supplemental pleading.
(f)Omitted Counterclaim. When a pleader fails to set up a counterclaim through oversight, inadvertence, or excusable neglect, or when justice requires, he may by leave of court set up the counterclaim by amendment.
(g)Cross Claim Against Coparty. A pleading may state as a cross claim any claim by one party against a coparty arising out of the transaction or occurrence that is the subject matter either of the original action or of a counterclaim therein or relating to any property that is the subject matter of the original action. Such cross claim may include a claim that the party against whom it is asserted is or may be liable to the cross claimant for all or part of a claim asserted in the action against the cross claimant.
(h)Joinder of Additional Parties. Persons other than those made parties to the original action may be made parties to a counterclaim or cross claim in accordance with the provisions of Rules 19 and 20.
(i)Separate Trials; Separate Judgments. If the court orders separate trials as provided in Rule 42(b), judgment on a counterclaim or cross claim may be rendered in accordance with the terms of Rule 54(b) when the court has jurisdiction so to do, even if the claims of the opposing party have been dismissed or otherwise disposed of.
(j)Claims Against Assignee. Except as otherwise provided by law as to negotiable instruments, any claim, counterclaim, or cross claim which could have been asserted against an assignor at the time of or before notice of an assignment, may be asserted against his assignee, to the extent that such claim, counterclaim, or cross claim does not exceed recovery upon the claim of the assignee.
(k)Claims Against Personal Representative. The death of a person shall not prejudice the rights of a third person to assert a claim, cross claim, or counterclaim surviving death against the personal representative of the deceased in the time and manner provided by law.
Rule 13 tells a party when a counterclaim is required and when it is optional. If a party has a claim against an opposing party that arises out of the same transaction or occurrence as the opposing party's claim, and resolving it does not require a third party the court cannot reach, the pleading must raise it — miss that window and the claim is generally lost. Narrow exceptions apply if the claim was already the subject of another pending suit, or if the opposing party's own suit was brought through attachment or similar process that never gave the court personal jurisdiction to render a money judgment. A claim unrelated to the opposing party's claim can still be brought as a permissive counterclaim, and a counterclaim may seek more, or something different in kind, than what the opposing party is seeking.
The rule also covers claims between coparties: a party may bring a cross-claim against a coparty arising from the same transaction as the original action, including a claim that the coparty is or may be liable for part of what is being sought from the cross-claimant. A counterclaim that matures or is acquired after a pleading is filed can be added later with the court's permission, and one left out by oversight, inadvertence, or excusable neglect can be added by amendment with leave of court. Additional parties needed for a counterclaim or cross-claim come in under the joinder rules, separate trials and judgments on these claims follow the usual rules for splitting up a case, and a claim that could have been asserted against an assignor can also be asserted against the assignee, up to what the assignee could recover.
Frequently Asked Questions
Do I have to bring my counterclaim now or can I sue separately later?
If the counterclaim arises out of the same transaction or occurrence as the opposing party's claim, Rule 13(a) requires it to be raised in the pleading or it is generally lost.
Can I bring a counterclaim that has nothing to do with the plaintiff's claim?
Yes — Rule 13(b) allows a permissive counterclaim against an opposing party even when it does not arise from the same transaction or occurrence.
What is the difference between a counterclaim and a cross-claim?
A counterclaim under Rule 13(a)-(b) is against an opposing party, while a cross-claim under Rule 13(g) is against a coparty, such as a codefendant, over a related claim or property.
I forgot to include a counterclaim in my answer, can I still add it?
Rule 13(f) lets a party add an omitted counterclaim by amendment with the court's permission when the omission was due to oversight, inadvertence, excusable neglect, or when justice requires it.
Source & verification. The rule text is reproduced verbatim from the
official Colorado Rules of Civil Procedure (Colo. R. Civ. P. 13). Prescribed by the Supreme Court of Colorado (C.R.S. § 13-2-108; Colo. Const. art. VI). The plain-English summary is original and written by us. Last verified July 10, 2026. ·
Official source
Also known as:compulsory counterclaim Coloradopermissive counterclaimcross claim against codefendantdo I have to file a counterclaimomitted counterclaim amendmentcounterclaim exceeding the claim