How to Answer a Complaint: Rule 8, Rule 12, and the Omissions That Waive Defenses

Answering a complaint means responding to every numbered allegation — admit it, deny it, or state that you lack knowledge sufficient to form a belief — then pleading every affirmative defense and compulsory counterclaim you have. In federal court the answer is due 21 days after service. Any allegation you do not deny is admitted.

That last sentence is Rule 8(b)(6), the most expensive line in the pleading rules.

This article is for general information and is not legal advice. For guidance on a specific case, consult a licensed attorney in your jurisdiction.

The clock

Rule 12(a) sets the federal deadlines. Docket the right row the day the complaint lands.

Two traps. The waiver clock runs from the date the request was sent, not the date you returned it. And the Rule 12(a)(4) reset is short: counsel who spend four months on a motion to dismiss are routinely surprised to owe an answer in fourteen days. File nothing and the plaintiff takes your default under Rule 55(a).

Answer, move to dismiss, or both?

Decide before you draft. A motion to dismiss is not free, and Rule 12(a)(4) means the answer gets written either way.

Move to dismiss when the defect is legal and no amendment fixes it. A limitations bar on the face of the complaint. No private right of action under the statute pleaded. Preemption. Immunity on the alleged facts. An exhibit that says the opposite of what the complaint says it says.

Answer when your best argument is that the complaint is thin. A motion saying "not enough facts" usually buys an amended complaint, not an exit. The Federal Judicial Center's study of motions to dismiss after Iqbal found 12(b)(6) filings rose from 2006 to 2010 with no general increase in grants without leave to amend. A dismissal with leave hands the plaintiff a roadmap you wrote.

Price the delay. S.D.N.Y. and E.D.N.Y. Local Civil Rule 6.1(b) is typical: 14 days to oppose, 7 to reply. Briefing is roughly three weeks of attorney time, and then the motion sits for months. If your documents are bad, you want that delay. Otherwise it is fees spent to postpone a pleading you file anyway.

The "both" path is usually smartest. Rule 12(b) lets you assert every defense in the responsive pleading, so you can answer on time, preserve everything, and move under Rule 12(c) once the pleadings close — or take the argument to summary judgment on a developed record. And if you move against only some counts, districts split on whether that suspends the time to answer the rest; the Federal Bar Association's survey collects the cases both ways.

Rule 8(b): admit, deny, or say you don't know

Rule 8(b)(1) requires an admission or denial of each allegation, and Rule 8(b)(2) adds that a denial "must fairly respond to the substance of the allegation." Track the complaint paragraph by paragraph, in its numbering. Where an allegation is partly true, Rule 8(b)(4) makes you "admit the part that is true and deny the rest."

Rule 8(b)(3) permits a general denial, but only from "a party that intends in good faith to deny all the allegations of a pleading — including the jurisdictional grounds." That disqualifies nearly every real answer: concede that you are a Delaware corporation and you cannot deny everything. Judges read a general denial in a case with admitted facts as a sign nobody worked the complaint, and some strike it.

What "lacks knowledge" actually means

Rule 8(b)(5) lets a party who "lacks knowledge or information sufficient to form a belief about the truth of an allegation" say so, and the statement operates as a denial. It is a genuine third option, not a way to avoid taking positions. Rule 11(b)(4) is the limit: denials must be "warranted on the evidence" or, if you flag them as such, "reasonably based on belief or a lack of information." Pleading want of knowledge about your own corporate records, your own employee's job title, or a recorded deed is a failure to look, and it surfaces at a deposition and then in a Rule 11 motion.

Rule 8(b)(6): silence is admission

"An allegation — other than one relating to the amount of damages — is admitted if a responsive pleading is required and the allegation is not denied." No motion, no hearing, no cure. Skip paragraph 47 and paragraph 47 is now a fact in the case. That is a proofreading failure more than a legal one, and the fix is in the checklist below.

Affirmative defenses under Rule 8(c)

Denials contest the plaintiff's facts. Affirmative defenses concede them and win anyway. Rule 8(c)(1) requires a party to "affirmatively state any avoidance or affirmative defense," and names eighteen:

accord and satisfaction, arbitration and award, assumption of risk, contributory negligence, duress, estoppel, failure of consideration, fraud, illegality, injury by fellow servant, laches, license, payment, release, res judicata, statute of frauds, statute of limitations, waiver

The list is illustrative. "Any avoidance" sweeps in unenumerated defenses — unclean hands, failure to mitigate, setoff — and the traditional consequence of omitting one is waiver. Our guide to affirmative defenses covers the burden shift and the case law.

How much detail each needs depends on where you sit. Twombly and Iqbal construed Rule 8(a)(2), which governs claims and requires a "showing"; Rule 8(c) says a defense must be "stated." District courts have split for years — some strike boilerplate defenses as conclusory, others hold that a defendant with 21 days cannot be held to the standard applied to a plaintiff who investigated for months.

The Second Circuit reached the question in GEOMC Co. v. Calmare Therapeutics Inc., 918 F.3d 92 (2d Cir. 2019), holding that plausibility does apply while cautioning that the inquiry is context-specific and that the shorter response window bears on how rigorously a defense is tested. Other circuits have not squarely resolved it. Do not assume GEOMC travels, and do not assume it does not.

Either way, plead what you can support and give each defense a sentence of factual content instead of a bare label. Learning what your own district does means hunting motions to strike decided by your judge, then confirming those rulings are still good law — the research CaseRead was built for. It searches public law and your firm's own case files together, so the answer you filed in that court two years ago surfaces beside the district's latest.

The Rule 12 defenses you lose by omission

Four defenses die if they are not in your first response.

Move under Rule 12 first and Rule 12(g)(2) bars a second Rule 12 motion raising an available defense you omitted. Answer instead, and those four belong in the answer.

Counterclaims and the Rule 15 fix

Rule 13(a) makes a counterclaim compulsory when it "arises out of the transaction or occurrence that is the subject matter of the opposing party's claim" and needs no party beyond the court's jurisdiction. Omit one and you generally lose it, because courts bar the later suit on res judicata or waiver grounds. Rule 13(b) counterclaims are permissive.

You also get one free amendment, and which provision governs depends on what your answer contains. A plain answer requires no responsive pleading, so Rule 15(a)(1)(A) gives you 21 days after serving it to amend as of course. If your answer pleads a counterclaim, courts generally apply Rule 15(a)(1)(B): 21 days after service of a responsive pleading or a Rule 12(b), (e), or (f) motion, whichever is earlier. After that, amendment takes consent or leave, which the court "should freely give when justice so requires." Freely is not automatically.

The pre-filing checklist

1. Docket the deadline from the right row of the Rule 12(a) table, plus a draft-complete date a week earlier.
2. Count paragraphs. Your numbering matches the complaint's, and every one carries an admission, a denial, or a Rule 8(b)(5) statement.
3. Audit each response against Rule 11(b)(4), splitting compound allegations instead of denying them whole.
4. Run the Rule 12(h)(1) four: personal jurisdiction, venue, process, service — in the answer or gone.
5. Work the Rule 8(c) list item by item, add the unenumerated avoidances, and give each defense a factual sentence.
6. Settle the counterclaim question, and confirm your authority is still good law before filing.

Frequently asked questions

How long do you have to answer a complaint?

Twenty-one days after service in federal court. If you timely returned a Rule 4(d) waiver, 60 days from the date the request was sent, or 90 days if it went outside any U.S. judicial district. The United States and its agencies get 60 days. State deadlines differ, so check the local rule.

What happens if you don't answer a complaint?

The plaintiff asks the clerk to enter your default under Rule 55(a), then seeks a default judgment. For a sum certain the clerk can enter judgment; otherwise the court determines damages. An entry of default can be set aside for good cause, but undoing a final default judgment requires Rule 60(b) relief.

Can you file a motion to dismiss instead of an answer?

Yes. A Rule 12(b) motion is filed before the responsive pleading, and Rule 12(a)(4) resets the answer deadline to 14 days after notice of the court's ruling. But Rule 12(g)(2) makes you consolidate every Rule 12 defense then available, and if the motion is denied you still write the answer.

What does denying for lack of knowledge mean in an answer?

Rule 8(b)(5) lets a party who lacks knowledge or information sufficient to form a belief about an allegation say so, and the statement has the effect of a denial. It is not a default response. Rule 11(b)(4) requires denials to be warranted on the evidence or, if flagged as such, reasonably based on belief or a lack of information, so facts sitting in your own file do not qualify.

Can you amend an answer after filing it?

Once as of right. An answer normally requires no responsive pleading, so Rule 15(a)(1)(A) gives you 21 days after serving it to amend without permission. After that you need the plaintiff's written consent or the court's leave, which the court should freely give when justice so requires. Leave gets harder as discovery closes.

Before it goes out the door

An answer is the cheapest place in a case to lose something permanently: 8(b)(6), 8(c), 12(h)(1), and 13(a) all punish omission rather than error, and none gives you a hearing.

If any part of the answer or a supporting memorandum was drafted with a general-purpose AI tool, run it through the Hallucination Shield first. It is free, needs no signup, and each citation it finds — up to 25 per run — is checked for existence and support. Filing a fabricated case in support of a defense is worse than the waiver you were worried about, and the opposition brief writes itself.