IL-1040, the Individual Income Tax Return, is the form the Illinois Department of Revenue (IDOR) uses to collect Illinois income tax from residents, part-year residents and nonresidents who have Illinois income or a refund to claim. This page covers the 2025 edition (R-12/25), which starts from your federal adjusted gross income and ends with your refund or the amount you owe. On FillingPDF you can fill out the form online and download or print the completed PDF; the original form and its instructions are published by IDOR at tax.illinois.gov.
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What is IL-1040?
Form IL-1040, Individual Income Tax Return, is the Illinois Department of Revenue (IDOR) form on which Illinois residents, part-year residents and nonresidents report income, subtractions, exemptions and credits for a tax year and figure their refund or the tax they owe.
The 2025 form is organized in twelve steps. Step 1 collects personal information, filing status and residency status. Steps 2 and 3 start from the adjusted gross income on your federal return, add Illinois additions and subtract items such as certain Social Security and retirement income to reach Illinois base income. Steps 4 to 7 apply the exemption allowance, compute the tax, subtract nonrefundable credits and add other taxes, including household employment tax and use tax. Steps 8 to 11 cover payments, refundable credits, any underpayment penalty, voluntary donations, and the refund or amount you owe. Step 12 holds the health insurance checkbox and the signature block.
Many lines point to schedules, among them Schedule NR, Schedule M, Schedule IL-E/EITC, Schedule CR, Schedule ICR and Schedule IL-WIT. Form IL-1040 is not used to change a return already filed: the instructions direct you to Form IL-1040-X, Amended Individual Income Tax Return, for that. Estimated payments use Form IL-1040-ES, and paper payments are sent with Form IL-1040-V, Payment Voucher for Individual Income Tax.
Who needs to file IL-1040?
The IDOR instructions set filing rules by group:
- Illinois residents file Form IL-1040 if they were required to file a federal return, or if they were not required to but their Illinois base income on Line 9 is greater than their exemption allowance. This includes residents who worked in Iowa, Kentucky, Michigan or Wisconsin and retired residents who filed a federal return.
- Part-year residents file with Schedule NR if they earned income while residents, earned Illinois-source income while nonresidents, or want a refund of withheld Illinois tax.
- Nonresidents file with Schedule NR if their Illinois-source income creates a tax liability or they want a refund of tax withheld in error. A nonresident whose only Illinois income is from partnerships, S corporations or trusts that withheld enough tax is not required to file.
- Residents of Iowa, Kentucky, Michigan or Wisconsin who worked in Illinois file only if they had Illinois income other than wages, salaries, tips and commissions, or want a refund of withheld tax.
- Dependents file if their Illinois base income exceeds the limit in the instructions or they want a refund of withheld tax.
- Nonresident aliens file if their income is taxed under federal law and attach federal Form 1040-NR.
- Surviving spouses and personal representatives file any return the deceased taxpayer was required to file.
Even if you are not required to file, you must file to get back Illinois tax withheld, estimated tax payments, or pass-through withholding.
When to file IL-1040
The due date to file and pay the 2025 Form IL-1040 is April 15, 2026, for calendar year filers; if that date falls on a weekend or holiday, the due date is the next business day. Fiscal-year filers enter their period at the top of the return, and the Illinois filing period matches the federal one.
IDOR grants an automatic six-month extension to file, which makes the extended due date October 15, 2026. A federal extension longer than six months is also allowed for Illinois. An extension does not extend the time to pay: if you expect to owe tax, pay it with Form IL-505-I, Automatic Extension Payment for Individuals, by April 15, 2026 to avoid penalty and interest.
If you cannot pay, file on time without payment to prevent a late-filing penalty; late-payment penalty and interest still run from the original due date. A return that is unsigned is treated as not filed.
Documents you need
- Federal Form 1040 or 1040-SR, page 1 and Schedule 1, with any W-2 and 1099 forms: attach when you enter federally tax-exempt income on Line 2 or a subtraction on Line 5.
- Forms W-2 and 1099 showing Illinois income and withholding, with Schedule IL-WIT: attach to support Illinois Income Tax withheld on Line 25.
- Schedule NR: attach if you check the Nonresident or Part-year resident box on Step 1, Line D.
- Schedule M and supporting documents: attach if you enter other additions on Line 3 or other subtractions on Line 7.
- Schedule IL-E/EITC: attach if you claim dependents on Line 10d, the Illinois Earned Income Tax Credit on Line 29 or the Child Tax Credit on Line 30.
- Schedule CR, pages 1 through 3: attach if you claim a credit for income tax paid to another state on Line 15.
- Schedule ICR: attach if you claim the property tax, K-12 education expense or volunteer emergency worker credit on Line 16.
- Schedule 1299-C and supporting documents: attach if you claim a credit on Line 17.
- Schedule 4255: attach if you enter recapture of investment tax credits on Line 13.
- Schedule K-1-P or K-1-T: attach if you claim pass-through withholding on Line 27 or pass-through entity tax credit on Line 28.
- Schedule G: attach if you make voluntary charitable donations on Line 35.
- Form IL-2210: attach if you check Line 34c because you annualized your income.
- Form IL-1310: attach when filing for a single deceased taxpayer and a refund is due.
- Federal Form 1040-NR: attach if you are a nonresident alien.
- Form IL-1040-V with your check or money order: staple to the front of the return if you send a payment.
How to fill out IL-1040
Enter your personal information
In Step 1, Line A, enter your name, full date of birth (MM/DD/YYYY), entire Social Security number (or ITIN), mailing address and email address, and your spouse's details if filing jointly. Add the Illinois county you lived in as of 12/31/2025 and, for a foreign address, the unabbreviated country name.
Select filing status and dependent status
On Line B check one filing status: Single, Married filing jointly, Married filing separately, Widowed or Head of household. On Line C check You and/or Spouse if someone can claim you as a dependent.
Mark your residency status
On Line D check Nonresident or Part-year resident if either applies during 2025, and attach Schedule NR. Full-year residents leave both boxes blank.
Report federal income and additions
Enter federal adjusted gross income on Line 1, federally tax-exempt interest and dividend income on Line 2, and other additions from Schedule M on Line 3. Add Lines 1 through 3 on Line 4, in whole dollars.
Figure your Illinois base income
Enter Social Security and certain retirement income on Line 5, any Illinois tax overpayment included in federal income on Line 6, and other Schedule M subtractions on Line 7. Add Lines 5 through 7 on Line 8 and subtract Line 8 from Line 4 on Line 9; if negative, enter 0.
Claim your exemption allowance
On Line 10a enter the exemption amount for you and your spouse using the chart in the instructions. Complete Lines 10b (65 or older), 10c (legally blind) and 10d (dependents from Schedule IL-E/EITC), then total them on Line 10.
Compute net income and tax
Residents subtract Line 10 from Line 9 on Line 11 and multiply as directed on Line 12. Nonresidents and part-year residents enter the amounts from Schedule NR. Add recapture from Schedule 4255 on Line 13 and total on Line 14.
Subtract nonrefundable credits
Enter credits on Line 15 (tax paid to another state), Line 16 (Schedule ICR) and Line 17 (Schedule 1299-C). Add them on Line 18, which cannot exceed Line 14, and subtract from Line 14 on Line 19.
Add other taxes
Enter household employment tax on Line 20, use tax from the UT Worksheet or UT Table on Line 21 (enter zero if none), and any surcharge on Line 22. Add Lines 19 through 22 on Line 23 for total tax.
Enter payments and refundable credits
Copy Line 23 to Line 24. Enter withholding (Line 25), estimated payments (Line 26), pass-through withholding (Line 27), pass-through entity tax credit (Line 28), Earned Income Tax credit (Line 29) and Child Tax credit (Line 30). Add Lines 25 through 30 on Line 31.
Figure the balance, penalty and donations
Use Line 32 if payments exceed tax, or Line 33 if tax exceeds payments. In Step 10, enter any underpayment penalty on Line 34 (checking boxes 34a to 34d if they apply) and donations on Line 35, then total them on Line 36.
Choose your refund or amount owed
For an overpayment, complete Line 37, enter the refunded amount on Line 38, check direct deposit or paper check on Line 39 and enter the amount credited forward on Line 40. If you owe, enter the amount on Line 41.
Complete the health insurance box and signature
Check Line 42 only if IDOR may share return information with the Department of Insurance, and include your email in Step 1. Sign and date; both spouses sign a joint return. Paid preparer and third party designee sections are completed only when they apply.
Review and download the completed PDF
Check every line for rounding to whole dollars and for matching Social Security numbers and names. Download or print the completed PDF from FillingPDF, then assemble the attachments listed above and file by one of the channels under How to submit.
How to submit IL-1040
You can file Form IL-1040 electronically or on paper by mail.
- Electronically: use MyTax Illinois at mytax.illinois.gov, which IDOR offers for free, a tax professional, or tax preparation software. IDOR says electronic filing with direct deposit is the fastest way to receive a refund.
- By mail, no payment enclosed: Illinois Department of Revenue, PO Box 19041, Springfield IL 62794-9041.
- By mail, payment enclosed: Illinois Department of Revenue, PO Box 19027, Springfield IL 62794-9027. Staple your check or money order and Form IL-1040-V to the front of the return.
- Payments: you may pay electronically through mytax.illinois.gov, by credit card (the card service provider charges a convenience fee), by check or money order payable to "Illinois Department of Revenue", in person at an IDOR Regional office, or in cash at the Springfield or Chicago IDOR office.
Staple Forms W-2 and 1099, schedules, powers of attorney and letters of estate to the return. For help, call IDOR at 1 800 732-8866 or 217 782-3336. FillingPDF lets you fill out and download the PDF; submission follows the channels above.
Common mistakes to avoid
- Leaving Line 21 blank. The instructions say you must make an entry for use tax and enter "zero" if you are not paying use tax on this form.
- Redacting your Social Security number. The instructions warn that this can cause processing delays, and the entire SSN is required.
- Mailing the return to the wrong P.O. box: one address is for returns without payment and another is for returns with payment.
- Filing a second Form IL-1040 to correct an earlier return instead of filing Form IL-1040-X, Amended Individual Income Tax Return.
- Submitting an unsigned return, or a joint return signed by only one spouse. An unsigned return is considered not filed and may bring a nonfiler penalty.
- Entering a refund amount on Line 38 without checking exactly one box on Line 39 for direct deposit or paper check.
- Choosing Qualifying Surviving Spouse as your filing status instead of Widowed, which the instructions say to use for QSS filers.
- Claiming tax withheld by an Iowa, Kentucky, Michigan or Wisconsin employer as a credit on Line 25 of your Illinois return.
- Forgetting to check the Nonresident or Part-year resident box on Line D, or to attach Schedule NR, when you were not a resident for the full year.
- Abbreviating the country name on the Foreign nation line when you have a foreign address.
Frequently asked questions
What is Form IL-1040 used for?
Form IL-1040 is the Illinois Department of Revenue's Individual Income Tax Return. You use it to report income, additions, subtractions, exemptions and credits for the tax year and to figure whether you get a refund or owe Illinois income tax. The 2025 edition is edition R-12/25.
Who has to file an Illinois IL-1040?
Illinois residents file if they had to file a federal return or their Illinois base income exceeds their exemption allowance. Part-year residents and nonresidents file with Schedule NR in the cases the instructions list. Anyone owed a refund of withheld or estimated tax must file.
When is the 2025 IL-1040 due?
April 15, 2026, for both filing and paying, for calendar year filers. IDOR grants an automatic six-month extension to file, to October 15, 2026, but it does not extend the time to pay; any tax owed is paid with Form IL-505-I by April 15, 2026.
Where do I mail my IL-1040?
Without payment, mail it to Illinois Department of Revenue, PO Box 19041, Springfield IL 62794-9041. With payment, mail it to PO Box 19027, Springfield IL 62794-9027, and staple your check or money order and Form IL-1040-V to the front.
Can I file the IL-1040 electronically?
Yes. IDOR encourages electronic filing through MyTax Illinois, which is free, through a tax professional or through tax preparation software. Almost all taxpayers can file electronically, and electronic filing with direct deposit is the fastest way to get a refund. The paper form is the alternative.
Do I have to enter something on Line 21 of the IL-1040?
Yes. Line 21 is use tax on internet, mail order and other out-of-state purchases, and the form says not to leave it blank. Use the UT Worksheet or UT Table in the instructions, and enter zero if you are not paying use tax on this form.
How do I correct an IL-1040 after I file it?
Do not file another Form IL-1040. File Form IL-1040-X, Amended Individual Income Tax Return, if you find an error or your federal return was changed in a final adjustment that affects your Illinois return.
Do I need to file IL-1040 if I only want a refund?
Yes. Even if you were not required to file, you must file Form IL-1040 to get a refund of Illinois tax withheld from your pay, estimated tax payments you made, or withholding passed through from a partnership, S corporation or trust.
Can I fill out Form IL-1040 online on FillingPDF?
Yes. You can fill out the PDF online on FillingPDF and download or print it. FillingPDF is an independent service and does not file the return with IDOR; you submit it through MyTax Illinois, a tax professional, software or by mail.
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