Who must file Form IL-1120 and when is its due date?

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You must file Form IL-1120, Corporation Income and Replacement Tax Return, if you are a corporation that

• has net income or loss as defined under the Illinois Income Tax Act (IITA); or
• is qualified to do business in the state of Illinois and is required to file a federal income tax return (regardless of net income or loss).

The Form IL-1120 original due date is based on the ending date of the tax year. 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.

Illinois grants an automatic extension of time to file your annual return. The automatic filing extension is also based on the ending date of the tax year.  For tax years ending on or after December 31, 2021, 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 seven months.
• June 30, we grant you an automatic extension of time to file your annual return of eight months.

For tax years beginning on or after January 1, 2016, and ending prior to December 31, 2021, 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.

For tax years beginning prior to January 1, 2016, 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 months regardless of when your tax year ends.

See our Corporation web page for more information. 

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