Do you make quarterly estimated tax payments?
Illinois estimated payments are due on the 15th day of the 4th, 6th, 9th, and 12th months of the tax year.
https://tax.illinois.gov/businesses/business-income-tax-estimated-payments.html#:~:text=Estimated%20....
Even if your taxes were paid in full, you could still be assessed a penalty if any of your estimated payments were made late.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
