An overpayment may occur when a claimant is paid unemployment insurance benefits and is later found to not be eligible for those benefits. To make an installment agreement, you will need to talk with IDES' Benefit Overpayment Collection at (800) 245-9762 (TDD (800) 662-3943).If you were overpaid on unemployment benefits from the Illinois Department of Employment Security (IDES), you may not have to pay that money back. Is there some waiver form I fill out? Do I just type out my own letter to appeal the overpayment with the reasons they mentioned? Submission of a Written Request: You may need to submit a formal request for a penalty waiver to the state's unemployment insurance agency. If the overpayment is due to reasons other than fraud, i.e.