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Due Date/Extension to File Income Tax Return (2023 IL-1040)

Your Illinois filing period is the same as your federal filing period. We will assume that you are filing your Form IL-1040 for the calendar year (January through December) unless you indicate a different filing period in the space provided at the top of the return. The original due date to file and pay Illinois individual income tax for calendar year filers is April 15, 2024. 

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 use 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 April 15, 2024.  MyTax Illinois is an easy way to pay your IL-505-I payment.