What is the due date of Form IL-1120?

  • Original due date:

    If your tax year ends on:

    • a date other than June 30, Form IL-1120 is due on or before the 15th day of the 4th month following the close of the tax year.
    • June 30, Form IL-1120 is due on or before the 15th day of the 3rd month following the close of the tax year.

    Note: If you are a cooperative, Form IL-1120 is due on the 15th day of the 9th month following the close of the tax year regardless of when your tax year ends.

  • Automatic filing extension:

    If your tax year ends on:

    • a date other than June 30, we grant you an automatic extension of time to file your annual return of six months.
    • June 30, we grant you an automatic extension of time to file your annual return of seven months.

    Note: If you are a cooperative, we grant you an automatic extension of time to file your annual return of seven month regardless of when your tax year ends.

     See our Corporations web page for more information.

If you have additional inquiries, you may submit them to the Questions, Comments, or Request form.