The Illinois Certificate of Ineligibility (COI) is issued by the Illinois Department of Human Services (IDs) to individuals who are not eligible for certain public benefits due to their immigration status. There are three types of Illinois COI: 1. Full Certificate of Ineligibility: This certificate is issued when an individual is not eligible for any public benefits. 2. Partial Certificate of Ineligibility: This certificate is issued when an individual is eligible for some, but not all, public benefits. 3. Temporary Certificate of Ineligibility: This certificate is issued when an individual is not eligible for public benefits at the time, but may become eligible in the future. The Illinois COI is used by public benefit agencies to determine an individual’s eligibility for certain public benefits, such as Medicaid and Temporary Assistance for Needy Families (TANK). The certificate includes information about the individual’s immigration status, as well as the public benefit programs for which they are ineligible. An individual must apply for an Illinois COI in order to receive public benefits.