A formal document issued under seal, commanding a person to whom it is addressed to do or refrain from doing a particular act.

When issued in the King’s or Queen’s Bench Division of the High Court of England & Wales, a Writ of Summons (colloquially referred to simply as a writ) was used to commence (originate) an action for damages or other relief. (Further particulars would then be set out in a Statement of Claim. Under the Civil Procedure Rules 1998 both writ and statement of claim are now incorporated into what is called a Claim Form.)

A judicial writ is one issued by the court under its own seal (eg a writ of prohibition).