Illinois State Taxes for International Students: Complete IL-1040 Guide

# Illinois State Taxes for International Students: Complete IL-1040 Guide

January 2026

Illinois is home to more than 70,000 international students — the fifth-highest of any state in the country. And with major universities like U of I Urbana-Champaign, University of Chicago, Northwestern, and UIC, there's a good chance you earned income somewhere in the state this year. If you did, you almost certainly need to file an Illinois state tax return.

Here's everything F1 students need to know about Illinois state taxes.

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Do I Need to File an Illinois State Tax Return?

Yes, if:

You earned income from Illinois sources (wages from an Illinois employer, on-campus jobs, OPT employment in Illinois)

Your Illinois base income exceeds your Illinois exemption allowance ($2,850 for single filers in 2025)

Illinois income tax was withheld from your paycheck and you want a refund

No, if:

You only filed Form 8843 at the federal level (no U.S. income)

All your income was earned outside Illinois

Your Illinois income fell below the $2,850 exemption threshold

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Am I a Resident or Nonresident of Illinois?

Here's where Illinois works a little differently from some other states. Illinois determines residency based on domicile — your permanent home, the place you intend to return to — rather than simply how many days you spent there. Since most F1 students still consider their home country (or another U.S. state) their permanent residence, they are nonresidents of Illinois for state tax purposes.

This is true even if you've been living in Chicago or Champaign for several years. Being here for school doesn't make Illinois your domicile.

Note that Illinois's definition of "nonresident" is separate from the federal nonresident alien classification. Illinois is looking at where your permanent home is, not the IRS Substantial Presence Test.

*As long as your permanent home remains outside Illinois.

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Which Form Do I File?

Unlike some states that have a dedicated nonresident return, Illinois uses one form for everyone: Form IL-1040, the Illinois Individual Income Tax Return. The difference is that nonresidents and part-year residents must also attach Schedule NR (Nonresident and Part-Year Resident Computation of Illinois Tax), which tells the state exactly how much of your income came from Illinois sources.

Think of IL-1040 as the main form and Schedule NR as the worksheet that makes it work for your situation.

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How Illinois Calculates Your Tax

Illinois has a flat income tax rate of 4.95%. There are no brackets — everyone pays the same percentage, whether you earned $15,000 or $150,000. This makes the math more straightforward than states like California with multiple tax brackets.

For nonresidents, here's how it works:

Schedule NR has two columns. Column A captures your total income from all sources (mirroring your federal return). Column B captures only the Illinois portion. Your tax is then calculated on the Column B amount at the flat 4.95% rate.

Example:

Total income (federal): $45,000

Illinois-source wages: $30,000

Illinois tax: $30,000 × 4.95% = $1,485

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Illinois Exemption Allowance (Not a Standard Deduction)

One thing that catches people off guard: Illinois does not have a standard deduction like the federal system or many other states. Instead, Illinois uses a personal exemption allowance.

For 2025, the exemption allowance is $2,850 for single filers. This amount is subtracted from your Illinois base income before the 4.95% rate is applied.

One thing to keep in mind: if your federal AGI exceeds $250,000 (single), this exemption is phased out entirely. That's unlikely to apply to most F1 students, but worth knowing.

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Does Illinois Honor Federal Tax Treaties?

Yes. Illinois does honor federal tax treaty provisions. This is good news — some states don't, which can create an unpleasant surprise after you've already excluded income at the federal level.

Because IL-1040 starts from your federal adjusted gross income, and because treaty-exempt income is already excluded from federal AGI, your treaty benefit generally carries through to your Illinois return without any additional add-back. If you're a Chinese national claiming the Article 20 exemption, or a student from another treaty country with a wage exemption, Illinois will respect that.

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No Chicago City Income Tax

If you worked in Chicago, you may be wondering whether there's a city-level income tax on top of state taxes — similar to how New York City residents pay an extra NYC tax. The good news: Chicago does not impose a local income tax. Neither does any other city in Illinois. Illinois prohibits local jurisdictions from levying income taxes, so what you owe at the state level is it.

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One Quirk: First-Time Illinois Filers Must Mail a Paper Return

This one trips up a lot of students. If you have never filed an Illinois return before, you cannot file electronically. You'll need to print, sign, and mail your IL-1040 and Schedule NR to the Illinois Department of Revenue. After your first return is processed, you'll receive an Illinois ID number/PIN that lets you file online in future years through the MyTax Illinois portal (mytax.illinois.gov).

Plan ahead — mailing a return adds a few weeks to the process, so don't wait until April 14th.

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Reciprocal Agreements with Neighboring States

Illinois has reciprocal tax agreements with Iowa, Kentucky, Michigan, and Wisconsin. If you're a resident of one of those states and earned wages in Illinois (or vice versa), you're generally exempt from paying income tax to the state where you worked — you'd only pay tax to your home state.

For most F1 students this won't come up, but it's relevant if you're on OPT and commuting across a state line.

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Common Situations for F1 Students in Illinois

Situation 1: On-Campus Job at U of I, UIUC, or Northwestern

Your wages are Illinois-source income. File IL-1040 + Schedule NR as a nonresident. Your Illinois tax is 4.95% on those wages minus the $2,850 exemption.

Situation 2: OPT Job in Chicago, School Was in Another State

If you physically worked in Illinois, those wages are Illinois-source income. File IL-1040 + Schedule NR. You may also need to file in the state where you previously worked or lived.

Situation 3: Worked Remotely for a Non-Illinois Company from Your Illinois Apartment

Generally, wages are taxed based on where the work is physically performed. If you were sitting in Champaign doing the work, Illinois can tax those wages even if your employer is headquartered elsewhere.

Situation 4: Internship in Another State, Then Returned to Illinois for School

File in the state where you physically worked during the internship. If you didn't earn wages while physically in Illinois, you may not need to file an IL-1040 at all.

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What If I Missed Filing in Previous Years?

If you worked in Illinois and didn't file a state return:

File late returns as soon as you can

You'll owe the original tax plus interest on unpaid amounts

Penalties can be reduced if you come forward before being contacted by the Illinois Department of Revenue

While USCIS doesn't directly verify state tax compliance during most immigration processes, being fully compliant across both federal and state obligations is always the right call.

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Illinois State Tax Deadline

The 2025 Illinois state tax deadline is April 15, 2026 — the same as the federal deadline.

If you need more time, Illinois offers an automatic 6-month extension to file (you'd have until October 15, 2026). However, this is only an extension to file — not to pay. If you owe taxes, you still need to pay by April 15 to avoid interest and penalties.

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What You'll Need to File

Completed federal Form 1040-NR (finish federal first — Illinois uses federal AGI as its starting point)

W-2 forms from any Illinois employer (Box 16 shows Illinois wages, Box 17 shows Illinois tax withheld)

Form 1042-S if you received scholarship income or treaty-exempt income

Your Illinois address during the tax year

Dates of Illinois residency if you were in multiple states

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Summary: Illinois Taxes for F1 Students at a Glance

Form: IL-1040 + Schedule NR

Tax rate: Flat 4.95%

Exemption: $2,850 (single, 2025)

Treaties: Honored

Local/city tax: None

Deadline: April 15, 2026

First-time filers: Must mail a paper return

Illinois's flat rate makes the math simpler than most states, but the Schedule NR and first-time paper filing requirement can still catch students off guard. Getting it right the first time means a smoother process every year after.