A summons (also in Britain known as a claim form) is a legal document issued by a court (a judicial summons) or by an administrative agency of government (an administrative summons) for various purposes.

Judicial summons

A judicial summons is addressed to a defendant in a legal proceeding. Typically, the summons will announce to the person to whom it is directed that a legal proceeding has been started against that person, and that a file has been started in the court records. The summons announces a date by which the defendant(s) must either appear in court, or respond in writing to the court or the opposing party or parties. The summons is the descendant of the writ of the common law. In ancient Persian law, if one failed to answer the summons of the King the punishment was death.

In England and Wales, the term writ of summons for the originating document in civil proceedings has been replaced with the term Claim Form by the Civil Procedure Rules 1998 (CPR). This is part of the reforms to simplify legal terminology.

In most U.S. jurisdictions, the service of a summons is in most cases required for the court to have personal jurisdiction over the party who is being "haled" into court involuntarily. The process by which a summons is served is called service of process. The form and content of service in the federal system is governed by Rule 4 the Federal Rules of Civil Procedure, and the rules of many state courts are similar. The federal summons is usually issued by the clerk of the court. In many states the summons may be issued by an attorney, though some states use filing as the means to commence an action and the summons must be filed in those cases in order to be effective. Other jurisdictions may only require that the summons be filed after it is served on the defendants.

Citation

thumb|right|upright|[[United States: The Ohio Uniform Traffic Ticket is a summons form prescribed by the Supreme Court of Ohio.]]
A citation, traffic violation ticket or notice to appear is a type of summons prepared and served at the scene of the occurrence by a law enforcement official, compelling the appearance of a defendant before the local magistrate within a certain period of time to answer for a minor traffic infraction or misdemeanor or other summary offence. Failure to appear within the allotted period of time is a separate crime of failure to appear.

Administrative summons

One example of an administrative summons is found in the tax law of the United States. The Internal Revenue Code authorizes the U.S. Internal Revenue Service (IRS) to issue a summons for a taxpayer—or any person having custody of books of account relating to a business of a taxpayer—to appear before the U.S. Secretary of the Treasury or his delegate (generally, this means the IRS employee who issued the summons) at the time and place named in the summons. The person summoned may be required to produce books, papers, records, or other data, and to give testimony under oath before an IRS employee.

The IRS is also empowered to issue the section 7602 summons for the purpose of "inquiring into any offense connected with the administration or enforcement of the internal revenue laws."

The summons may be enforced by a court order, and the law provides a criminal penalty of up to one year in prison or a fine, or both, for failure to obey the summons, except that the person summoned may, to the extent applicable, assert a privilege against self incrimination or other evidentiary privileges, if applicable.