The State of Illinois has issued the following guidance regarding income tax filing deadlines for the 2023 tax year:
- The filing deadline for 2023 tax returns is April 15, 2024
- The payment deadline is also April 15, 2024. Penalties and interest on underpayments will be calculated from that date
- 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.