Who must file Form IL-1120?

You must file Form IL-1120, Illinois 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).

See the IL-1120 Instructions for due dates and filing requirements.

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