You will owe a late-payment penalty for unpaid tax if you do not pay the tax you owe by the original due date of the return, even if you have an extension of time to file. The penalty rate is based on the number of days the payment is late. For more information refer to
Form IL-2210, Computation of Penalties for Individuals.
If you have additional inquiries, you may submit them to the Questions, Comments, or Request form.