Illinois Additional Defendant Signatures, Names, & addresses are legal documents required when initiating a court proceeding in Illinois. These documents must include the signatures of all defendants involved in the case as well as their full names and addresses. There are two types of Illinois Additional Defendant Signatures, Names, & addresses: those submitted to the court during the filing of the complaint and those submitted to the court during the service of the summons. Both types must be completed accurately and signed by the defendants in order for the case to move forward.