If you filed your return electronically before March 15, 2021, you do not need to do anything. The Illinois Department of Revenue (IDOR) is planning to automatically update your Adjusted Gross Income (AGI) beginning next month. Once your return has been adjusted, you will receive a letter from IDOR explaining the update, and if you are entitled to a refund a paper check will be mailed to the address on file. If you disagree with the changes, you may respond to the letter.