Illinois AO 213-Vendor Information/TIN Certification is a form used by Illinois vendors to certify their taxpayer identification number (TIN) with the State of Illinois. This form is used by all vendors who are required to register with the State of Illinois to obtain a TIN and is used as a part of the Vendor Registration process. It is also used to update the TIN information of existing vendors. There are two types of Illinois AO 213-Vendor Information/TIN Certification: the AO 213-Vendor Information/TIN Certification For New Vendors and the AO 213-Vendor Information/TIN Certification For Existing Vendors.