A part-year resident taxpayer (i.e., you were a resident of Illinois for part but not all of the tax year), must file Form IL-1040 and Schedule NR, Nonresident and Part-Year Resident Computation of Illinois Tax, if any of the following is true:
- you earned income from any source while you were a resident
- you earned income from Illinois sources while you were not a resident
- you want a refund of any Illinois Income Tax withheld
A nonresident taxpayer (i.e., you were not an Illinois resident at any time during the tax year), must file Form IL-1040 and Schedule NR if any of the following is treu:
- 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 50 is greater than your Illinois exemption allowance on Schedule NR, Step 5, Line 54)
- you want a refund of any Illinois Income Tax withheld in error. You must attach a letter of explanation from your employer


