Rule 13 Counterclaims and Crossclaims: Filing, Waiver, and Timing

Federal Rule of Civil Procedure 13 governs counterclaims and crossclaims: it requires a defendant to raise any claim against the plaintiff that grows out of the same events as the lawsuit, permits unrelated claims against the plaintiff at the party’s option, and lets co-parties sue each other over matters tied to the case. Miss a required counterclaim, and you lose it permanently.¹

A counterclaim is a claim one party asserts against an opposing party inside the same lawsuit. A crossclaim goes sideways, from one co-party to another on the same side. The distinction between a counterclaim and a defense matters: a defense says the plaintiff shouldn’t win; a counterclaim says the plaintiff owes you too, and it can seek any amount and any kind of relief, even if that dwarfs or has nothing to do with what the plaintiff asked for.

Compulsory Counterclaims

Rule 13(a) makes a counterclaim compulsory when it arises out of the same “transaction or occurrence” as the plaintiff’s claim. If two drivers collide and Driver A sues Driver B for injuries, Driver B’s own injury claim from that same collision is compulsory. The claims share a common core of facts, so they belong in the same case.¹

The phrase “transaction or occurrence” is deliberately broad. Courts most commonly ask whether there is a logical relationship between the two claims, looking at whether the same evidence would support or refute both, whether the factual and legal issues overlap significantly, and whether hearing them separately could produce inconsistent results. A yes to any of those usually means the counterclaim is compulsory.

The Waiver Penalty

This is where Rule 13 has real teeth. If you have a compulsory counterclaim and don’t raise it, you lose it. Once the case ends without the counterclaim being asserted, claim preclusion bars you from bringing it in a later lawsuit.¹ A defendant who fixates on beating the plaintiff’s case and forgets to assert a related claim can win the lawsuit and still permanently forfeit the right to seek their own damages. That mistake happens more often than you’d think, and it’s almost always irreversible.

Narrow Exceptions

Rule 13(a)(2) excuses a compulsory counterclaim in two situations:

The claim was already the subject of another pending lawsuit when the current case began.
The opposing party sued through a process, such as attachment, that didn’t establish personal jurisdiction over you, and you choose not to file any counterclaim at all.

A compulsory counterclaim is also excused when asserting it would require adding a party the court cannot obtain jurisdiction over.¹

Permissive Counterclaims

A permissive counterclaim is any claim against the opposing party that doesn’t arise from the same transaction or occurrence as the plaintiff’s case. If you’re sued for breaching a supply contract and you happen to have an unrelated claim against the same plaintiff for an unpaid loan, that loan claim is permissive.¹ You can include it in the current case, or save it for a separate lawsuit. There’s no waiver penalty for holding it back.

The tradeoff is strategic, and jurisdictional. Because a permissive counterclaim is unrelated to the original claim, it typically doesn’t qualify for supplemental jurisdiction under 28 U.S.C. § 1367, which reaches only claims that form part of the same controversy as the original case.² A permissive counterclaim needs its own independent basis for federal jurisdiction, either diversity of citizenship with more than $75,000 at stake or a federal question. Without one, the court will dismiss it, and you’ll have to sue separately.

Compulsory counterclaims, by contrast, almost always ride along on supplemental jurisdiction, because sharing the same transaction is exactly what § 1367 requires. The same reasoning generally covers crossclaims, which must also relate to the underlying case.

Crossclaims Against Co-Parties

A crossclaim is a claim against someone on the same side of the case, most often one co-defendant against another. It must arise from the transaction or occurrence behind the original suit or a counterclaim already in the case, or involve property at issue in the original action.¹

Crossclaims are always optional. A co-party is never forced to file one and faces no penalty for reserving the claim for a separate lawsuit. The choice usually comes down to whether it’s more efficient to resolve the dispute now, while the underlying case is already being litigated, or to hold it for later.

When and How to File

Counterclaims and crossclaims are filed inside the Answer to the complaint. That is the default vehicle, and compulsory counterclaims must be included at that stage. Missing the Answer deadline without raising a compulsory counterclaim is where most Rule 13 problems begin.¹

If You File a Rule 12 Motion First

If you file a motion to dismiss under Rule 12(b) before answering, you don’t need to include counterclaims in that motion. Rule 12 motions are a separate procedural step that precedes the responsive pleading.³ If the motion is denied and you’re ordered to answer, that’s when your obligation to assert compulsory counterclaims kicks in. Filing a Rule 12 motion effectively buys more time, since the Answer deadline is typically extended while the motion is pending.

Adding a Counterclaim After the Answer

Sometimes a party realizes after answering that a compulsory counterclaim was left out, or a new claim develops later. Rule 13 addresses both:

For a counterclaim omitted through oversight or excusable neglect, you can ask the court for leave to amend your Answer. Under Rule 15, amendments are generally granted freely when justice requires, but “freely” is not “automatically.” Delay and prejudice to the other side count against you.
For a counterclaim that matures or is acquired after the Answer was served, the court can permit a supplemental pleading to assert it.¹

Neither route is guaranteed. The earlier you catch the problem, the better the odds of getting permission to add the claim.

Bringing In Additional Parties

A counterclaim or crossclaim sometimes involves people who aren’t yet in the lawsuit. Rule 13(h) incorporates the joinder rules from Rules 19 and 20, which govern required and permissive joinder.¹ If your claim can’t be fully resolved without an outside party, you can move to add them, and the court evaluates the request under the same standards that apply to any other party-addition, including whether it has jurisdiction over the new party.

1
Legal Information Institute. Federal Rules of Civil Procedure Rule 13 – Counterclaim and Crossclaim
2
GovInfo. 28 USC 1367 – Supplemental Jurisdiction
3
Legal Information Institute. Federal Rules of Civil Procedure Rule 12 – Defenses and Objections