Follow the directions in the related answer below provided by a fellow TurboTax agent.
https://ttlc.intuit.com/replies/6256459
You will need to mail your return to the address listed below that applies to your situation.
If no payment is enclosed, mail your return to:
Illinois Department of Revenue
Springfield IL 62719-0001
If a payment is enclosed, mail your return to:
ILLINOIS DEPARTMENT OF REVENUE
Springfield, IL 62726-0001
