Most filers ask the same things. Do I have to file in Illinois? Which schedules do I need? How does my federal return carry over? How do I pay, get a refund, or fix a mistake?
This guide answers those questions using the 2025 tax year (filed in 2026). Rates, exemptions, deadlines, and form versions can change each year, so check the current IDOR instructions before you file.
Key Takeaways
- Residents, part-year residents, and some nonresidents with Illinois-source income may need to file IL-1040.
- Gather your federal return, income documents, withholding records, and credit paperwork first.
- An extension gives more time to file, not more time to pay.
- Keep every confirmation, and use Form IL-1040-X to correct errors.
Who Must File Form IL-1040?
Residents, part-year residents, and nonresidents
Full-year residents. Illinois defines a resident by domicile: the place you live and intend to return to after temporary absences. A resident generally must file if required to file a federal return. A resident must also file if Illinois base income exceeds the Illinois exemption allowance, even without a federal filing requirement.
Part-year residents. File IL-1040 with Schedule NR if any of these apply:
- You earned or received income while an Illinois resident.
- You received Illinois-source income while a nonresident.
- You are due an Illinois refund.
Illinois generally taxes all income received while you were a resident, plus Illinois-source income received as a nonresident.
Nonresidents. File with Schedule NR if Illinois-source income creates a tax liability, or if Illinois withholding was taken in error and you want it back. Wages for work done in Illinois, Illinois rental income, and Illinois business income are typical examples.
No tax due does not mean no return. You may still need to file to recover Illinois withholding, claim estimated payments, or collect refundable credits.
Federal Form 1040 versus Illinois Form IL-1040
The IRS describes Form 1040 as the annual federal individual return. Illinois starts from your federal adjusted gross income (AGI), then applies Illinois additions, subtractions, exemptions, credits, and payments.
"Which Form 1040 should I use?" is a federal question. Most people use Form 1040, and qualifying older taxpayers may use the 1040-SR alternative. IL-1040 is the state return in every case.
Income earned in other states can create extra filing obligations there. Schedule CR may give Illinois residents a credit for qualifying income tax paid to another state. For wages earned in Iowa, Kentucky, Michigan, or Wisconsin, IDOR tells residents to include the wages in Illinois income and not claim Schedule CR for those states' withholding.
If you have foreign income, remote-work arrangements, or more than one home, confirm sourcing and residency rules before filing.
Gather Your Documents and Identify Required Illinois Schedules
Documents to collect before starting
Pull these together first:
Income and filing base
- Your federal Form 1040 and all schedules
- W-2s, 1099s, and brokerage statements
- Records of Illinois withholding
- Your prior-year Illinois return
- Estimated-payment confirmations
- Records of other income, including self-employment and retirement income
Credits, residency, and identity
- Residency records if you moved
- Dependent details, property tax bills, K-12 education expense receipts, and charitable records
- Proof of taxes paid to other states
- Your SSN or ITIN, current mailing address, and bank routing and account numbers
Store copies securely. You will need them if IDOR asks questions later.
Common Illinois schedules and related forms
| Form | What it does |
|---|---|
| Schedule NR | Computes Illinois tax for nonresidents and part-year residents |
| Schedule IL-WIT | Reports Illinois income tax withholding (attach W-2s/1099s) |
| Schedule IL-E/EITC | Covers exemptions and the Illinois Earned Income Tax Credit |
| Schedule ICR | Figures property tax, K-12 education expense, and Volunteer Emergency Worker credits |
| Schedule M | Lists Illinois additions and subtractions |
| Schedule CR | Credit for qualifying income taxes paid to other states |
Related forms sit outside the schedule set:
- IL-1040-ES covers estimated payments
- IL-1040-V is the voucher for mailed payments
- IL-1040-X amends a filed return
Match each form to the correct tax year. Download current versions directly from IDOR rather than relying on older lists.
How to Complete Form IL-1040: Step-by-Step
Follow the 2025 IL-1040 instructions line by line. The steps below show the flow.
Enter taxpayer information, dependents, and filing status
Enter names, addresses, SSNs or ITINs, spouse details, and dependents exactly as they appear on your federal return. Mismatches are a common cause of processing delays.
Marriage, divorce, a death in the family, a move into or out of Illinois, or a dependent change can all affect your schedules. Review them before you start.
Transfer and reconcile income information
Start with your federal return, then check it against W-2s, 1099s, brokerage statements, retirement records, and self-employment records.
Federal AGI is not the final Illinois base. Schedule M adds and subtracts specific items:
- Additions include certain child tax-exempt interest and earnings from 529 and ABLE programs
- Subtractions include eligible Social Security and retirement income and qualifying U.S. government interest
Only listed subtractions are allowed.
Do not skip income because no wage statement shows it. Interest, dividends, unemployment compensation, self-employment income, and capital gains all count.
Apply Illinois exemptions, subtractions, and credits
The sequence runs from federal AGI, through Illinois additions and subtractions, to exemptions, net income, tax, then withholding, estimated payments, and credits.
For 2025:
- Personal exemption: $2,850 per exemption. An extra $1,000 applies for a qualifying taxpayer or spouse who is 65 or older or legally blind.
- Exemption limit: The allowance is reduced when AGI exceeds $250,000 ($500,000 if married filing jointly).
- Illinois EITC: 20% of the federal EITC.
- Property tax credit: Generally 5% of qualifying property taxes on your principal residence. Nonresidents cannot claim it.
- K-12 education expense credit: 25% of qualified expenses above the first $250, up to $750.
Eligibility depends on filing status, income, age, dependents, residency, and documentation. Combined Schedule ICR credits cannot exceed your tax due. Don't assume you qualify; read the current schedule instructions.
Calculate the balance due or refund
Illinois uses a flat individual income tax rate of 4.95% for 2025. Your final liability reflects net income, exemptions, adjustments, credits, withholding, and estimated payments.
Compare the Illinois tax shown on your wage statements and payment confirmations with what you report on the return. Then work out which situation you're in:
- Balance due: Your tax exceeds payments and credits.
- Overpayment: Payments exceed your tax.
- Refundable credit: A credit such as the EITC can produce a refund even when no tax was withheld.
A refund is only the excess of payments and credits over tax due, not the total tax you paid.
Review, sign, submit, and retain
Before you submit, check:
- SSNs or ITINs and filing status
- Residency and income figures
- Attached schedules and W-2/1099 copies showing withholding
- Bank details and payment amounts
- Signatures
Save the filed return, supporting documents, e-file acceptance notice, payment confirmation, and any IDOR letters.
Returns involving multi-state income, foreign income, nonresident issues, or amendments get complicated fast. VJM Global prepares Form 1040 and Form 1040-NR returns and assists with federal and state filings, so it can help in those situations.
How to File, Pay, and Track Your Illinois Return
Deadlines and extensions
The tax year is the year you earned income. The filing year is when you file. For tax year 2025, the return and any payment are due April 15, 2026.
IDOR grants an automatic six-month filing extension to October 15, 2026. That extends the filing date only. If you expect to owe, estimate the amount and pay by April 15.
Estimated-tax installment dates, amended-return deadlines, and annual filing dates are separate. Don't mix them up.
Electronic and paper filing options
You can file through MyTax Illinois at no charge, but eligibility is limited. Conditions include:
- An accepted 2024 IL-1040 on file
- Full-year Illinois residency
- An SSN or ITIN
- A valid email address
MyTax also excludes certain income types, schedules, and credits, so check IDOR's full list. Approved commercial tax software is another route. Providers may charge fees and may not support every Illinois situation.
Paper filing works if you use the current-year form package and the correct mailing address. Save your e-file acceptance or proof of mailing either way.
Paying Illinois tax
IDOR accepts:
- Electronic payment from a checking or savings account through MyTax Illinois
- Credit card payment through its card service, with a 2.25% convenience fee (minimum $1)
- A mailed check or money order with Form IL-1040-V
Select the correct tax year and payment type. Filing and paying can be separate steps, so keep a confirmation for each.
Refunds and return tracking
Choose direct deposit and double-check routing and account numbers. IDOR says e-filed returns with direct deposit are the fastest route. E-filed refunds are generally expected in about four weeks, and paper returns in four to eight weeks.
Track yours with IDOR's Where's My Refund tool. The IDOR refund FAQs explain that security reviews, missing information, and errors can cause delays. Respond quickly to any IDOR letter.
Recordkeeping and data security
IDOR's instructions say to keep supporting records for at least three years from the due date or filing date, whichever is later. The IRS general rule is also three years, with seven years for claims involving a worthless security or bad debt. Keep prior-year returns too, since you'll need them for e-filing eligibility and amendments.
Protect your data:
- Share SSNs, ITINs, and bank details only through secure portals or encrypted file sharing.
- Never send them by plain email.
- Ignore unsolicited refund or payment texts. IDOR says it will not ask for personal or financial information by text.
Special Situations, Extensions, and Corrections
Part-year, nonresident, and multi-state taxpayers
Schedule NR allocates income between Illinois and everywhere else. Part-year residents report all income from their resident period plus Illinois-source income from the nonresident period.
Schedule CR applies when you paid tax to another state on income also taxed by Illinois. You must have filed a required return with that state.
Part-year residents can only claim credit on income earned while an Illinois resident. Nonresidents cannot claim it at all.
IDOR's guidance on employee compensation says a nonresident who performs significant, nonincidental work in Illinois for more than 30 working days may have Illinois-source pay, apportioned by Illinois workdays. This covers only employee compensation, not every remote-work scenario.
Remote workers, business owners, investors, and anyone with foreign or cross-border income should get a professional review.
Late filing, late payment, and estimated taxes
Late filing, late payment, and interest are separate issues. Under IDOR's penalty guidance:
- Late-filing penalty: The lesser of $250 or 2% of the tax required to be shown due. It can apply even with no tax due.
- Late-payment penalty: 2% when 1 to 30 days late, 10% at 31 days or more.
- Interest: Simple, calculated daily. IDOR lists 7% for January 1, 2025 through December 31, 2026.
If you can't pay in full, file a complete return on time anyway. It prevents the late-filing penalty, though not late-payment consequences. An extension payment does not replace filing by the extended deadline.
Estimated tax (2026): Payments are required when expected Illinois liability exceeds $1,000 after withholding and credits. Calendar-year installments are due April 15, June 15, and September 15, 2026, and January 15, 2027. Check the current IL-1040-ES for details.
Correcting an Illinois return
Use Form IL-1040-X to fix omitted income, incorrect withholding, missed credits, filing-status errors, or changes from a federal adjustment.
Gather:
- The original IL-1040
- Corrected schedules
- A revised federal return or IRS notice, if relevant
- Payment records and supporting evidence
Federal changes carry strict timing:
- Tax increase: File IL-1040-X and pay within 120 days of federal finalization.
- Refund claim: File generally within two years plus 120 days of federal finalization. Where applicable, wait until the IRS accepts the federal change.
Frequently Asked Questions
How much is $100,000 a year after taxes in Illinois?
It depends on filing status, deductions, credits, and withholding. For a single filer on 2025 wages with the standard deduction, take-home is roughly $74,000 after federal tax, 4.95% Illinois tax, and FICA. That is an estimate, not your final liability.
What is the federal and state tax in Illinois?
Federal tax follows federal brackets, while Illinois imposes its own flat 4.95% rate for 2025. Illinois tax is calculated after exemptions, additions, subtractions, and credits.
Which Form 1040 should I use?
Form 1040 is the federal series, and the right version depends on your federal situation. Form 1040-SR is an option for qualifying older taxpayers. IL-1040 is the separate Illinois return.
Do I have to file an Illinois tax return?
Residents generally must file if they have a federal filing requirement or Illinois base income above the exemption allowance. Part-year residents and nonresidents with Illinois-source income may also need to file. You can also file to recover withholding or claim credits; confirm current IDOR rules.
Is 1040 the same as the federal income tax return?
Form 1040 is the main federal individual income tax return. IL-1040 is a separate state return that starts from your federal figures.
