Your Illinois filing period is the same as your federal filing period. We will assume that you are filing your
Form IL-1040, Individual Income Tax Return, for the calendar year unless you indicate a different filing period in the space provided at the top of the return. The due date for calendar year filers is April 15 of the year following the tax year of your return, unless April 15 falls on a weekend or holiday.
We grant an automatic six-month extension of time to file your return. If you receive a federal extension of more than six months, you are automatically allowed that extension for Illinois. These extensions do not grant you an extension of time to pay any tax you owe. If you determine that you will owe tax, you must file
Form IL-505-I, Automatic Extension Payment for individuals, to pay any tax you owe to avoid penalty and interest on tax not paid by the original due date.