You should prepare your federal tax return before completing your state tax return. Form 1040 (federal return) will be used throughout completing your state return.  

Illinois’ state tax filing is completed using form IL-1040, which can be filed directly online for free through the mytax.illinois.gov portal. If you have never filed a tax return in the state of Illinois before, you will have to file using a physical form mailed to IDOR (the Illinois Department of Revenue) – no individual completing an Illinois state return for the first time can file and pay online. Once you’ve filed your first return, you will receive an Illinois ID number/PIN, which you can use to file and pay online in subsequent years. The mailing addresses is listed at the end of the recorded session.

If you would like to request a PDF copy of the presentation, please email gradhelp@uchicago.edu

The following categories are used for residency in Illinois:

  • Full-year resident: maintained a legal place of residence in Illinois from January 1 through December 31. You do not have to be physically present in Illinois the entire year to be considered a full-year resident. File state taxes using IL-1040.
  • Part-year resident: established Illinois resident during the year or were an Illinois resident but established residency in another state during the year. File state taxes using IL-1040 and Schedule NR.
  • Nonresident: you are a full-year resident of a state other than Illinois. File state taxes using IL-1040 and Schedule NR.

Please keep in mind you can be considered a non-resident for tax purposes by the federal government and the IRS and simultaneously be a resident of the state of Illinois.

Illinois State Taxes FAQ

If you have a state tax obligation but need more time before you file, you can request a filing extension by submitting form IL-505-I. Please keep in mind that form IL-505-I is only an extension to file your state return – it is not an extension on paying state taxes that are owed. Any owed taxes paid late may be assessed a penalty.

Unfortunately, we have heard from IDOR that they do not have the ability to accept payments without an associated US taxpayer ID. If you don’t yet have an SSN or ITIN, we recommend submitting form IL-505-I and submitting the prepared return (IL-1040) and paying once the SSN or ITIN has been received. You will likely be assessed a late payment penalty, but IDOR has acknowledged that this specific situation would likely be grounds for abatement of the penalty.

We unfortunately cannot provide specific information about filing requirements for states other than Illinois, although there are some reciprocal agreements that may apply in this situation. A full list of each individual state's department of revenue in maintained by the IRS (https://www.irs.gov/businesses/small-businesses-self-employed/state-government-websites).