The Illinois Letter to the Sheriff for Service of Summons (SCA) is an official court document used in the state of Illinois to serve a summons on a defendant in a civil case. It is a letter from the plaintiff, or their attorney, to the local sheriff's office asking them to serve the summons on the defendant. It includes the names of the parties involved, the case number, the court where the case is pending, the date the summons was issued, and the name and address of the defendant. There are two types of Illinois Letter to the Sheriff for Service of Summons (SCA): the Original Summons and the Substituted Summons. The Original Summons is used when the defendant is known and the address is known. The Substituted Summons is used when the defendant is not known or their address is unknown.