What federal forms must I attach to my Form IL-1120-ST, Small Business Corporation Replacement Tax Return?

When filing your return there are certain types of income items and subtraction modifications that require the attachment of Illinois or federal forms and schedules. Instructions for these attachments appear throughout the specific Form IL-1120-ST instructions for completing your return.

All taxpayers, including unitary business groups, must attach a copy of your U.S. Form 1120S, Pages 1 through 5, to your Illinois return if you are required to file federally.

Note: When filing your Form IL-1120-ST include only forms and schedules required to support your return. Do not attach correspondence to your return.

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