If you are an Illinois resident, you must file Form IL-1040, Individual Income Tax return, if

1. you filed a federal income tax return;
2. you were not required to file a federal income tax return, but your Illinois base income was greater than your Illinois exemption allowance; or
3. you are claimed on your parents' or another person's return and your Illinois base income is greater than your Illinois base income is greater than $2,000.

Even if you are not required to file Form IL-1040, you must file to get a refund of any Illinois Income Tax withheld from your pay or any estimated tax payments you made.