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Filing Requirements

Who must file an Illinois tax return?

If you were

  • an Illinois resident, you must file Form IL-1040 if
    • you were required to file a federal income tax return, or
    • you were not required to file a federal income tax return, but your Illinois base income from Line 9 is greater than your Illinois exemption allowance.
  • an Illinois resident who worked in Iowa, Kentucky, Michigan, or Wisconsin, you must file Form IL-1040 and include as Illinois income any compensation you received from an employer in these states. Compensation paid to Illinois residents working in these states is taxed by Illinois. Based on reciprocal agreements between Illinois and these states, these states do not tax the compensation of Illinois residents.

    If your employer in any of these states withheld that state’s tax from your compensation, you may file the correct form with that state to claim a refund. You may not use tax withheld by an employer for these states as a credit on your Illinois return.

  • a retired Illinois resident who filed a federal return, you must file Form IL-1040. However, certain types of retirement income ( e.g., pension, Social Security, railroad retirement, governmental deferred compensation) may be subtracted from your Illinois income. For more information, see the instructions for Line 5 and Publication 120, Retirement Income.
  • a part-year resident , you must file Form IL-1040 and Schedule NR, Nonresident and Part-Year Resident Computation of Illinois Tax, if
    • you earned income from any source while you were a resident,
    • you earned income from Illinois sources while you were not a resident, or
    • you want a refund of any Illinois Income Tax withheld.
  • a nonresident, you must file Form IL-1040 and Schedule NR if
    • you earned enough taxable income from Illinois sources to have a tax liability ( i.e., your Illinois base income from Schedule NR, Step 5, Line 46, is greater than your Illinois exemption allowance on Schedule NR, Step 5, Line 50), or
    • you want a refund of any Illinois Income Tax withheld in error. You must attach a letter of explanation from your employer.

    NOTE: If you are a nonresident and your only income in Illinois is from one or more partnerships, S corporations, or trusts that withheld enough Illinois Income Tax to pay your liability, you are not required to file a Form IL-1040.

  • an Iowa, Kentucky, Michigan, or Wisconsin resident who worked in Illinois, you must file Form IL-1040 and Schedule NR if
    • you received income in Illinois from sources other than wages, salaries, tips, and commissions, or
    • you want a refund of any Illinois Income Tax withheld.

    If you received wages, salaries, tips, and commissions from Illinois employers, you are not required to pay Illinois Income Tax on this income. This is based on reciprocal agreements between Illinois and these states.

    The reciprocal agreements do not apply to any other income you might have received, such as Illinois lottery winnings.

  • an Illinois resident who was claimed as a dependent on your parents’ or another person’s return, you must file Form IL-1040 if
    • your Illinois base income from Line 9 is greater than your Illinois exemption allowance, or
    • you want a refund of Illinois Income Tax withheld from your pay.

    NOTE: If your parent reported your interest and dividend income through federal Form 8814, Parent’s Election to Report Child’s Interest and Dividends, do not count that income in determining if you must file your own Form IL-1040.

  • the surviving spouse or representative of a deceased taxpayer who was required to file in Illinois, you must file any return required of that taxpayer. Please refer to the special instructions on how to file for a deceased taxpayer.
  • a student, you are not exempt from tax nor are there special residency provisions for you. However, income, such as certain scholarships or fellowships, that is not taxable under federal income tax law, is also not taxed by Illinois.
  • a nonresident alien, you must file Form IL-1040 if your income is taxed under federal income tax law. You must attach a copy of your federal Form 1040NR, U.S. Nonresident Alien Income Tax Return, or federal Form 1040NR-EZ, U.S. Income Tax Return for Certain Nonresident Aliens With No Dependents.

Even if you are not required to file Form IL-1040, you must file to get a refund of

  • Illinois Income Tax withheld from your pay,
  • estimated tax payments you made, or
  • withholding on income passed through to you by a partnership, S Corporation, or trust.