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If my Illinois tax increases as a result of my federal change, how long do I have to amend and pay the additional liability?

If your federal change increases your Illinois tax, you must file Form IL-1040-X and pay any additional tax within 120 days of the federal finalization date or you may be assessed a late-payment penalty.

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You may access additional information by searching the entire Illinois Department of Revenue website.

If you have additional inquiries, you may submit them on the Questions, Comments, or Requests form.