Illinois Certificate Of Mailing Notice is a document that is used to demonstrate that a mailing was sent to a particular recipient. It is issued by the United States Postal Service (USPS) and is used to prove that a mailing was sent to a particular person or business. The certificate includes the name and address of the sender, the date the mailing was sent, and a unique tracking number assigned to the mailing. There are two types of Illinois Certificate Of Mailing Notice: Domestic Certificate of Mailing and International Certificate of Mailing. The Domestic Certificate of Mailing is issued for mailings sent within the United States. The International Certificate of Mailing is issued for mailings sent outside the United States. Both certificates are used to prove that the mailing was sent to the intended recipient.