The Illinois Department of Revenue (IDOR) sends letters and notices to request additional information and support for information you report on your tax return. An overpayment may occur when a claimant is paid unemployment insurance benefits and is later found to not be eligible for those benefits.And when I appeal for a waiver, is there a form I fill out or just send my own letter to them or what? All forms are ADA accessible, and you can handwrite or type into the PDF form to fill it out. Check a Claim's Status.