Illinois Additional Proof of Service is a document that is filed with the court to certify that a defendant has been formally served with a legal document. In Illinois, there are three types of Additional Proof of Service: ordinary proof of service, personal service, and certified mail service. Ordinary Proof of Service requires the proof of service to be signed by the person who served the document, and it should include the date and time of service, the manner of service, and the address where the document was served. Personal Service requires the proof of service to be signed by the person who served the document, as well as a witness who is not related to either the plaintiff or defendant. The proof of service must include the date and time of service, the manner of service, a description of the document served, and the address where the document was served. Certified Mail Service requires the proof of service to be a US Postal Service Form 3800, which includes the date and time of service, the manner of service, a description of the document served, and the address where the document was served.