Complaint Law and Legal Definition

In a lawsuit or administrative dispute, a complaint is the initial document filed with the court or other authority by a person or entity claiming legal rights against another. The party filing the complaint is usually called the plaintiff and the party against whom the complaint is filed is called the defendant or defendants. Complaints must properly state the factual as well as legal basis for the claim. A complaint also must follow statutory requirements, which vary by jurisdiction. When the complaint is filed, a copy of the complaint and the summons must be served on a defendant before a response is required.

For example, a complaint may be formal papers issued by the NLRB to start an unfair labor practice hearing before an Administrative Law Judge. The complaint states the basis for the Board's jurisdiction and the alleged unfair labor practice.