The Illinois Department of Revenue (IDOR) sends letters and notices to request additional information and support for information you report on your tax return. Instructions for completing the UI-28 are on Page 2.The UI-28 Form is on Pages 3 and 4. Want to check on the status of your individual Illinois income tax refund? Just provide us with your Social Security number, first and last name. Forms on this website are PDFs with fillable fields. Forms should be downloaded to your computer before filling in the fields. You may submit refunds online in real-time using our Electronic Refund Management tool. The only prerequisite is registration with Availity Essentials. Claiming a Property.