In law, a plaint is the formal written document a person files with a court to begin a civil lawsuit. It identifies the parties, explains why the court has authority to hear the dispute, describes what happened, and tells the court what the person filing wants done about it. The term is largely archaic in the United States: American courts call the same document a “complaint” (or, in some proceedings, a “petition”). The function is identical, and because U.S. practice overwhelmingly uses “complaint,” that is the word that governs the rules described below.
Where the Word “Plaint” Still Appears
You will run into “plaint” in older legal texts and in other common law systems, particularly India and the United Kingdom, where it still carries formal legal significance. If you are reading an American statute, court rule, or form today, expect to see “complaint” instead. The person filing is the plaintiff; the document they file is the complaint; and the rules that follow come from the Federal Rules of Civil Procedure, which govern federal civil cases and shape most state rules closely.
What a Complaint Must Contain
Federal Rule of Civil Procedure 8 sets out the three core requirements for any complaint: a short and plain statement of the grounds for the court’s jurisdiction, a short and plain statement of the claim showing the plaintiff is entitled to relief, and a demand for the relief sought.1Office of the Law Revision Counsel. 28 USC App Fed R Civ P Rule 8 – General Rules of Pleading
Each of those three elements carries real weight:
- Jurisdiction. The complaint has to explain why this particular court can hear the case. In federal court, that usually means the dispute involves a federal law (federal question jurisdiction) or the parties are from different states and the amount in dispute exceeds a statutory threshold (diversity jurisdiction). Without a proper jurisdictional basis, the court can dismiss before anything else happens.
- Statement of the claim. This is the story of the dispute, told in numbered paragraphs. It identifies the parties, describes what the defendant did or failed to do, and explains how that conduct caused harm. The facts need to be specific enough that a reader can see why the plaintiff believes they are entitled to a legal remedy.
- Demand for relief. The complaint has to spell out what the plaintiff wants. That might be money damages, a court order directing or prohibiting conduct, return of property, or specific performance of a contract. A plaintiff can request multiple types of relief in the alternative.
Rule 10 adds formatting: the complaint needs a caption with the court’s name, a title naming all the parties, and a file number. Claims must be stated in numbered paragraphs, each limited as much as possible to a single set of facts.2Legal Information Institute. Fed R Civ P 10 – Form of Pleadings
Signature, Not Sworn Verification
A common misunderstanding is that every complaint must be sworn to under oath. It does not. Rule 11 says a pleading need not be verified or accompanied by an affidavit unless a specific rule or statute requires it. What is required is a signature. Every complaint must be signed by at least one attorney of record, or by the party personally if they are self-represented. That signature is a certification: by signing, the attorney or party represents that the factual claims have evidentiary support (or will likely have it after reasonable investigation) and that the legal arguments are grounded in existing law or a good-faith argument for changing it.3Legal Information Institute. Rule 11 – Signing Pleadings, Motions, and Other Papers; Representations to the Court; Sanctions Certain specific case types do require sworn verification, but those are exceptions.
How a Complaint Gets Filed
Filing means submitting the complaint to the correct court, paying the required fee, and getting it into the court’s record system. The plaintiff first has to pick a court with proper jurisdiction and venue; filing in the wrong one wastes time and money because the case gets dismissed or transferred. Courts charge a filing fee that varies by court system and sometimes by the amount in dispute. Most federal courts now require attorneys to file electronically through the CM/ECF system; self-represented parties sometimes have different rules and may still be allowed to file on paper.
Issuance and Service of the Summons
Filing puts the case on the court’s docket, but the defendant does not know about it yet. After the complaint is filed, the plaintiff presents a summons to the court clerk for signature and seal. The clerk issues the summons, and the plaintiff is responsible for having it served on the defendant along with a copy of the complaint.4Legal Information Institute. Federal Rules of Civil Procedure Rule 4 – Summons The summons tells the defendant that a lawsuit has been filed, states the deadline for responding, and warns that failing to respond will result in a default judgment.5United States Courts. AO 440 Summons in a Civil Action Service has to follow specific rules about who can deliver the summons and how.
The Defendant’s Deadline To Respond
In federal court, a defendant generally has 21 days after being served to file an answer or a motion challenging the complaint. If the defendant timely waived formal service, that window extends to 60 days, or 90 days if the defendant is outside the United States. The U.S. government, its agencies, and federal officers sued in their official capacity get 60 days after service on the U.S. Attorney.6Legal Information Institute. Rule 12 – Defenses and Objections: When and How Presented
What Happens If the Defendant Ignores It
Ignoring a lawsuit does not make it disappear. When a defendant fails to respond within the deadline, the plaintiff can ask the court clerk to enter a “default,” a formal notation that the defendant did not appear. From there, the plaintiff can seek a default judgment.7Legal Information Institute. Rule 55 – Default; Default Judgment
If the claim is for a specific sum that can be calculated precisely, the clerk can enter judgment directly. For everything else, the plaintiff has to ask the court for a hearing, where a judge may take evidence to set damages or verify the allegations. If the defendant appeared in the case at any point before defaulting, they must receive at least seven days’ written notice before a default judgment hearing. Courts can set aside a default for good cause, but the bar rises once an actual judgment has been entered.7Legal Information Institute. Rule 55 – Default; Default Judgment
How a Defendant Can Challenge the Complaint
Instead of answering, a defendant can file a motion to dismiss under Rule 12(b), arguing that a fundamental flaw should end the case before it goes further. Rule 12(b) recognizes seven grounds:6Legal Information Institute. Rule 12 – Defenses and Objections: When and How Presented
- Lack of subject-matter jurisdiction (the court lacks authority over this type of case).
- Lack of personal jurisdiction (the court lacks authority over this defendant).
- Improper venue (wrong geographic court).
- Insufficient process (the summons was defective).
- Insufficient service of process (the summons was not delivered properly).
- Failure to state a claim (even if everything alleged is true, it does not amount to a legal violation).
- Failure to join a required party.
A motion to dismiss has to come before the answer. Some of these defenses, including lack of personal jurisdiction and improper venue, are waived permanently if the defendant does not raise them in the first responsive filing. Subject-matter jurisdiction, by contrast, can be raised at any point, even on appeal.
Amending the Complaint
Complaints are not fixed. Rule 15 lets a plaintiff amend the complaint once without needing the court’s permission, as long as it is done within 21 days after serving the original complaint. If the defendant has already filed an answer or a motion to dismiss, the window shifts to 21 days after that filing, whichever comes first.8Legal Information Institute. Rule 15 – Amended and Supplemental Pleadings After that initial window, the plaintiff needs either the defendant’s written consent or the court’s leave. Courts are generally willing to allow amendment unless the opposing party would be unfairly prejudiced or the amendment would be futile.
Sanctions for a Baseless Filing
The signature on a complaint is not just a formality. Rule 11 empowers courts to sanction any attorney, law firm, or party who files a complaint that lacks a reasonable factual or legal basis, or that is filed for an improper purpose such as harassment or delay. Sanctions can include orders to pay the other side’s attorney’s fees, monetary penalties paid to the court, or nonmonetary directives, and they must be limited to what is sufficient to deter repetition. A court cannot impose monetary sanctions on a represented party for making weak legal arguments; that penalty falls on the attorney.3Legal Information Institute. Rule 11 – Signing Pleadings, Motions, and Other Papers; Representations to the Court; Sanctions
The Filing Deadline That Overrides Everything
Every civil claim has a deadline for filing, known as the statute of limitations. Miss it, and the court will dismiss the case regardless of how strong the underlying claim is. These deadlines vary by claim type and jurisdiction. Contract disputes, personal injury, fraud, and property damage each carry different limitation periods, and the clock typically starts from the date the harm occurred or was discovered. Because the complaint is the document that stops the clock, filing it before the deadline expires is one of the most time-sensitive decisions in any civil dispute. If you think you have a civil claim, identifying the applicable deadline is the first step toward preserving your right to sue.