Chicago, IL (CAPITOL CITY NOW) – The Illinois Department of Revenue is reminding taxpayers to file an amended return if they discover an error on a previously filed state income tax return.

“It’s not uncommon for taxpayers to spot an error after they’ve filed their returns,” said IDOR Director David Harris. “Amending a return is a straightforward way to make it right and ensures taxpayers are paying exactly what they owe—or getting the refunds they’re due.”

How to File an Amended Return:
Use the Correct Form – Always file Form IL-1040-X to amend an individual income tax return.
Include Supporting Documents – If you are amending due to a federal adjustment, wait until the Internal Revenue Service (IRS) finalizes it, and include supporting proof with your amended return.

Provide a Clear Explanation – Use Step 11, Line D of Form IL-1040-X to clearly explain the reason for the amendment. Incomplete or unclear explanations may delay processing.

Sign and Date the Form – Both taxpayers must sign and date the form if filing jointly.

Submit the Completed Return – Taxpayers can file electronically through the modernized-file system (MeF) starting with the 2021 tax year and may also send completed forms and documents by mail.

“If a taxpayer finds a mistake, it’s best to correct it without delay,” Director Harris said. “Promptly filing an amended return will help avoid unnecessary penalties and interest if additional tax is owed—and if a refund is due, it will result in getting the money back faster.”

For complete instructions, taxpayers can refer to the Form IL-1040-X instructions, available on the IDOR website. Additional help is available by visiting tax.illinois.gov or calling 1-800-732-8866 or 217-782-3336.