To file a counterclaim, you include it inside your answer to the plaintiff’s complaint and file that document with the court, generally within 21 days of being served. It is not a separate lawsuit and not a separate filing. The counterclaim needs a jurisdictional statement, numbered factual allegations, one or more counts identifying the legal theory, and a request for specific relief. If your claim arises from the same transaction as the plaintiff’s, filing it now is mandatory: skip it and you lose it for good.
Decide Whether Filing Now Is Mandatory
Federal Rule of Civil Procedure 13 divides counterclaims into two categories, and the category controls your deadline pressure.
A compulsory counterclaim arises out of the same transaction or event as the plaintiff’s lawsuit. If a homeowner sues a contractor for shoddy work and the contractor believes the homeowner still owes money under the same contract, the contractor’s claim for unpaid fees is compulsory. You must raise it in your answer, or it is permanently barred. There is no second chance in a later lawsuit.1Legal Information Institute. Federal Rules of Civil Procedure Rule 13 – Counterclaim and Crossclaim
A permissive counterclaim involves a dispute that does not arise from the same transaction. If that same contractor separately loaned the homeowner money for something unrelated, a claim to collect on the loan is permissive. You can raise it in the current case, or you can bring a separate lawsuit later without losing it.1Legal Information Institute. Federal Rules of Civil Procedure Rule 13 – Counterclaim and Crossclaim
One boundary worth noting. A counterclaim is a claim against the opposing party. A claim against a co-defendant on your own side of the case is a crossclaim under Rule 13(g), governed by different procedural rules.1Legal Information Institute. Federal Rules of Civil Procedure Rule 13 – Counterclaim and Crossclaim
Jurisdiction matters too. A compulsory counterclaim rides on supplemental jurisdiction under 28 U.S.C. § 1367 because it shares the same underlying facts as the main case.2GovInfo. 28 USC 1367 – Supplemental Jurisdiction A permissive counterclaim historically needed its own independent basis for federal jurisdiction, such as diversity or a federal question. Some federal courts now read § 1367 more broadly, but the law is not settled across circuits. If your counterclaim is permissive and you are in federal court, confirm an independent jurisdictional basis before you file.
Know the 21-Day Deadline
Your counterclaim is filed as part of your answer, and Rule 12 gives you 21 days after service of the complaint to file that answer.3Legal Information Institute. Federal Rules of Civil Procedure Rule 12 – Defenses and Objections Miss the answer deadline and your counterclaim goes down with it.
Already filed an answer without one? Rule 15 gives you a path back. You can amend your answer once as a matter of course within 21 days after serving it, or within 21 days after the plaintiff files a responsive pleading or a Rule 12 motion, whichever comes first. After that window, you need the plaintiff’s written consent or the court’s permission. Courts are directed to grant leave “freely when justice so requires,” but the longer you wait, the harder the argument.4Legal Information Institute. Federal Rules of Civil Procedure Rule 15 – Amended and Supplemental Pleadings
Prepare the Substance Before Drafting
A counterclaim has to stand on its own as a viable legal claim. Identify the legal theory first: breach of contract, fraud, negligence, whatever fits your facts. Then work backward from the elements of that theory to figure out what evidence you actually have.
Gather every document that supports your position: contracts, invoices, emails, text messages, photographs, financial records. Identify anyone who witnessed the key events or can speak to your damages. Put the material in chronological order so the story translates cleanly into numbered paragraphs. Gaps in the factual record are where counterclaims fall apart, so be honest with yourself about what you can prove before committing to specific allegations.
Build the Document
Rule 8 requires every pleading stating a claim for relief, counterclaims included, to contain a statement of the court’s jurisdiction, a plain statement of the claim showing you are entitled to relief, and a demand for the relief you want.5Office of the Law Revision Counsel. Federal Rules of Civil Procedure Rule 8 – General Rules of Pleading Rule 10 adds a caption with the court’s name, a title, and the case number, and requires claims to be stated in numbered paragraphs, each limited to a single set of circumstances.6Legal Information Institute. Federal Rules of Civil Procedure Rule 10 – Form of Pleadings
A working counterclaim usually contains:
- A caption showing the court, case number, parties, and a title like “Answer and Counterclaim.”
- A short statement identifying you as the defendant/counter-plaintiff and the plaintiff as the counter-defendant.
- A jurisdictional statement. For a compulsory counterclaim, a reference to supplemental jurisdiction under 28 U.S.C. § 1367 is standard.
- Numbered factual allegations, one fact or event per paragraph.
- Separate counts (Count I, Count II) naming the legal theory and tying it to the facts you alleged.
- A prayer for relief specifying what you want: dollar amounts, declaratory relief, or other remedies.
Your counterclaim can seek more than the plaintiff sought, and it can seek a different kind of relief. Rule 13(c) says a counterclaim “may claim relief exceeding in amount or different in kind from that sought in the pleading of the opposing party.”1Legal Information Institute. Federal Rules of Civil Procedure Rule 13 – Counterclaim and Crossclaim
A Worked Example
Assume a homeowner (Smith) sues a contractor (Jones) for allegedly defective kitchen remodeling. Jones believes Smith refused to pay the remaining $18,000 balance on the contract and wants to recover it. The counterclaim portion of Jones’s answer might read like this:
UNITED STATES DISTRICT COURT
EASTERN DISTRICT OF [STATE]
ALEX SMITH, Plaintiff,
v.
JORDAN JONES d/b/a JONES CONTRACTING, Defendant.
Case No. 26-cv-01234
DEFENDANT’S ANSWER AND COUNTERCLAIM
[Answer section responding to plaintiff’s complaint would appear here.]
COUNTERCLAIM
Defendant Jordan Jones, by way of counterclaim against Plaintiff Alex Smith, alleges as follows:
JURISDICTION
1. This counterclaim arises out of the same transaction that forms the basis of Plaintiff’s complaint. The Court has supplemental jurisdiction under 28 U.S.C. § 1367.
FACTUAL ALLEGATIONS
2. On January 15, 2026, Smith and Jones entered into a written contract for the renovation of the kitchen at Smith’s residence located at [address].
3. The total contract price was $45,000, payable in three installments: $15,000 at signing, $12,000 at the midpoint of the project, and $18,000 upon completion.
4. Smith paid the first two installments totaling $27,000.
5. Jones completed all work described in the contract on or about April 10, 2026, in accordance with the contract specifications.
6. On April 12, 2026, Jones submitted a final invoice to Smith for the remaining $18,000.
7. Smith has refused to pay the final installment despite repeated written demands.
COUNT I — BREACH OF CONTRACT
8. Jones incorporates by reference the allegations in paragraphs 1 through 7.
9. A valid and enforceable contract existed between Smith and Jones.
10. Jones fully performed all obligations under the contract.
11. Smith breached the contract by failing to pay the final installment of $18,000.
12. Jones has suffered damages in the amount of $18,000 as a direct result of Smith’s breach.
PRAYER FOR RELIEF
WHEREFORE, Defendant Jordan Jones respectfully requests that this Court enter judgment against Plaintiff Alex Smith as follows:
a) Awarding Jones damages in the amount of $18,000;
b) Awarding pre-judgment interest;
c) Awarding costs of this action; and
d) Granting such other relief as the Court deems just and proper.
This is a compulsory counterclaim because it arises from the same contract at the center of the plaintiff’s lawsuit. If Jones did not raise it here, Jones could not bring a separate lawsuit later to collect the $18,000.1Legal Information Institute. Federal Rules of Civil Procedure Rule 13 – Counterclaim and Crossclaim
File It and Serve the Plaintiff
File the counterclaim with your answer at the court clerk’s office where the original lawsuit is pending. Most federal courts use the CM/ECF electronic filing system, which requires a PACER account and separate access credentials from the specific court.7United States Courts. Electronic Filing (CM/ECF) If e-filing is not available to you, ask the clerk about filing in person or by mail.
In federal court, adding a counterclaim to your answer generally does not carry a separate filing fee beyond the initial appearance fee. State court rules vary; check your local fee schedule.
Because the plaintiff is already a party, Rule 5 governs service and the methods are simpler than initial service of process.8Legal Information Institute. Federal Rules of Civil Procedure Rule 5 – Serving and Filing Pleadings and Other Papers Acceptable methods include:
- Electronic filing through CM/ECF, which counts as service automatically if the opposing attorney is a registered user.
- Regular mail to the person’s last known address. Service is complete when the document goes into the mail.
- Hand delivery to the person or leaving it at their office with someone in charge.
- Any other method the other party consented to in writing, including email.
If you serve through the court’s e-filing system, no certificate of service is required. For any other method, file a short certificate of service confirming how, when, and on whom you served the document, either with the counterclaim or within a reasonable time afterward. Keep a copy.8Legal Information Institute. Federal Rules of Civil Procedure Rule 5 – Serving and Filing Pleadings and Other Papers
What Happens Next
Once served, the plaintiff has 21 days to respond to your counterclaim, just as you had to respond to the complaint.3Legal Information Institute. Federal Rules of Civil Procedure Rule 12 – Defenses and Objections The plaintiff can answer, raise affirmative defenses, or move to dismiss on grounds such as failure to state a claim, lack of jurisdiction, or an expired statute of limitations.
From there, the counterclaim and the original claim move through discovery and trial together. Both sides gather evidence on both claims at once, which is one of the efficiencies of the counterclaim system: related disputes get resolved in a single proceeding rather than two.
At judgment, if both sides win on their respective claims, the court offsets the awards. In the Smith and Jones example, if the court found Smith was owed $8,000 for defective work and Jones was owed $18,000 on the unpaid balance, the net judgment would be $10,000 in Jones’s favor. A successful counterclaim can reduce the plaintiff’s recovery to zero or flip the case so the plaintiff owes you. You are not capped at the amount the plaintiff sought.