Introduction
Form IL-1040 is Illinois's individual income tax return. It is separate from the federal Form 1040, though your federal return supplies the starting number. For Australians with Illinois ties, such as a former US resident, a remote worker or an investor, residency and sourcing rules can be confusing.
Most taxpayers want the same answers:
- Do I have to file?
- What documents do I need?
- When is it due, and how do I pay or get a refund?
One caution up front. Tax year 2027 is the income year; you file the return in the following filing season.
As of late 2026, the Illinois Department of Revenue (IDOR) had published a 2027 IL-1040-ES estimated-payment draft but no 2027 annual return. This guide uses the final 2025 package as its framework.
Confirm every date, rate, threshold and form version with IDOR before filing. All amounts are in US dollars.
Key Takeaways
- Residents, part-year residents and some nonresidents with Illinois-source income may need to file.
- Gather your federal return, income statements, withholding records and bank details first.
- Verify the 2027 rate, exemption, deadline and payment steps with IDOR.
- An extension gives more time to file, not to pay.
- Keep copies of everything, and use IL-1040-X to fix errors.
Who Must File Form IL-1040 for Tax Year 2027?
Residents, part-year residents and nonresidents
Your status drives the obligation. Under the 2025 instructions:
- Resident: domiciled in Illinois all year. File if a federal return is required, or if Illinois base income exceeds the exemption allowance even without a federal filing obligation.
- Part-year resident: file IL-1040 with Schedule NR to report income from the resident period, plus Illinois-source income while a nonresident.
- Nonresident: file with Schedule NR if Illinois-source income creates tax, or to recover withholding taken in error.
Domicile means where you live and intend to return after temporary absences. Foreign residence can be a temporary absence. An Australian address alone does not end Illinois residency, so check your facts against the current definitions.
Filing when no tax is owed
A zero balance does not always mean no filing. Illinois may still require a return based on income, residency or Illinois-source income. Filing can also help you:
- Claim refundable credits such as the Illinois EITC
- Recover Illinois withholding
- Document your position
If you need no federal return, the instructions still say to use Form 1040 as an AGI worksheet.
Federal Form 1040 versus Illinois IL-1040
Form 1040 goes to the IRS. IL-1040 goes to Illinois. Completing one does not satisfy the other.
Illinois starts with federal adjusted gross income (AGI), not federal taxable income. It then applies Illinois additions, subtractions, exemptions and credits.
Income connected to another state
If you earned income in another state, you may have a separate filing duty there. Illinois offers Schedule CR for tax paid to other states. Remote workers, business owners, investors and people with more than one home should confirm sourcing and residency rules before filing.
Gather Your Documents and Identify Required Illinois Schedules
Documents to collect
- Federal Form 1040 and schedules
- W-2s, 1099s and other income records
- Illinois withholding details
- Prior-year Illinois return
- Records for exemptions, credits and other-state taxes
- Bank details for direct deposit or electronic payment
Common related forms and schedules
| Form or schedule | Purpose |
|---|---|
| IL-1040-X | Amend a filed return |
| IL-1040-ES | Estimated tax payments |
| IL-1040-V | Payment voucher for mailed payments |
| Schedule NR | Part-year and nonresident computation |
| Schedule CR | Credit for tax paid to other states |
| Schedule ICR | Property tax, K-12 education expense and Volunteer Emergency Worker credits |
| Schedule IL-WIT | Illinois tax withheld |
| Schedule IL-E/EITC | Exemptions, Illinois EITC and Child Tax Credit |
| Schedule M | Other additions and subtractions |
Note that IDOR now titles the exemptions and credits schedule "IL-E/EITC". Confirm 2027 names and versions on IDOR's forms page rather than relying on an older list.
Organizing records and protecting personal information
Sort records by income, withholding, credits, payments and residency. Keep copies of what you submit.
Protect Social Security numbers, taxpayer ID numbers and bank details:
- Use encrypted storage
- Avoid emailing documents unprotected
- Share them only through secure channels
How to Complete Form IL-1040: Step-by-Step
Enter taxpayer information and filing status
Enter names, addresses, SSNs or ITINs, filing status and dependents exactly as your records show. A move into or out of Illinois affects residency status and may bring in Schedule NR.
Transfer and reconcile income
Use your federal return and income statements to find the figures Illinois needs. Do not assume every federal line carries over unchanged. Wages, self-employment income, interest, dividends, retirement income and capital gains each need a check against Illinois treatment.
Apply additions, subtractions, exemptions and credits
The 2025 framework works like this: federal AGI plus Illinois additions, minus Illinois subtractions, gives base income. The exemption allowance then helps determine net income.
- Federally tax-exempt interest is added back.
- Certain retirement income can be subtracted.
- The exemption was $2,850 for 2025 and $2,925 for 2026. Confirm the 2027 amount in the official instructions.
- No allowance applies if federal AGI exceeds $500,000 (married filing jointly) or $250,000 (other statuses), per the IDOR exemption bulletin.
- The 2025 Illinois EITC is 20% of the federal credit.
Calculate tax, withholding and balance due
Illinois law sets a rate of 4.95% of net income for years beginning on or after July 1, 2017. That rate remains in statute, so confirm it in the 2027 instructions before you file.
Then reconcile withholding, estimated payments, prior payments and refundable credits against your W-2s, 1099s and payment confirmations to find the refund or balance due.
Review, sign, submit and retain
Before submitting, check:
- Names and ID numbers
- Residency and filing status
- Income and schedules
- Bank details
- Arithmetic and consistency with the federal return
- Signatures and attachments
E-file gives an acceptance confirmation. If you mail a paper return, keep proof of mailing. VJM Global prepares federal and state returns using IRS-compliant processes, which can help if your return is complex.
How to File, Pay, and Track Your Illinois Return
Deadlines: tax year versus filing year
The standard deadline is April 15, or the next business day if it falls on a weekend or holiday. For the 2025 return, that was April 15, 2026. A 2027 return would fall in 2028; confirm the exact date with IDOR.
Filing, payment, estimate and amendment deadlines are separate. The automatic six-month extension (to October 15 for 2025 returns) does not extend payment.
Electronic and paper filing
IDOR's free MyTax Illinois has limits. For 2025 it required:
- A 2024 IL-1040 on file
- Full-year Illinois residency
- An SSN or ITIN
- Supported income and credits
Nonresident returns do not qualify. Other authorized e-file methods and paper IL-1040 remain options. The IRS Free File AGI limit of $89,000 for 2025 returns is a different test.
Paying online
IDOR accepts:
- Bank account payment through MyTax
- Credit card through Illinois E-Pay (the page lists a 2.25% fee, minimum $1)
- Mailed check or money order with Form IL-1040-V
Choose the correct tax year and payment type, and save the confirmation. Verify fees before paying.
Refunds, direct deposit and recordkeeping
IDOR's "Where's My Refund?" tool updates each business day. A paper check may replace direct deposit for first-time filers, unverified accounts or banks outside the US. Keep the return, supporting documents, payment and e-file confirmations, and any IDOR notices ready for inspection.
When professional support helps
Consider a qualified tax professional if you have:
- Multi-state income, or part-year or nonresident status
- Self-employment or complex foreign income
- Amended returns, large balances or an Illinois notice
VJM Global's U.S.-compliant tax professionals support US individual return preparation, including Form 1040 and 1040-NR. Confirm the scope of any engagement for your Illinois return directly.
Special Situations, Extensions, and Corrections
Part-year, nonresident and multi-state taxpayers
Schedule NR allocates income for people who moved or earned Illinois-source income. Schedule CR gives a credit equal to the lesser of eligible other-state tax and Illinois tax on that income. Nonresidents cannot claim it, and part-year residents claim it only for resident-period income.
In the official example, a couple moved from Indiana in April. With $40,500 of $54,000 in wages tied to the Illinois period and $1,000 of other-state tax, the allocation is $750.
Schedule CR excludes foreign-country taxes. Australian income tax cannot be credited there.
Extensions, estimates and late filing
The six-month extension covers filing only. Interest runs from the day after payment was due. Under IDOR's Publication 103:
- Late payment: 2% for 1-30 days, 10% for 31 or more days
- Late filing: the lesser of $250 or 2% of tax required, with further penalties after notice
Estimated payments apply if expected liability exceeds $1,000 after withholding and credits. The 2026 installments fall on April 15, June 15, September 15 and January 15, 2027. Use the 2027 IL-1040-ES for 2027 estimates.
Correcting an error after filing
File IL-1040-X for omitted income, wrong withholding, missed credits or federal adjustments. Timing rules from the 2025 instructions:
- Federal change increasing Illinois tax: file and pay within 120 days of federal finalisation
- Federal change decreasing tax: claim within two years plus 120 days
- State-only refund change: generally three years from the later of the original or extended due date, or one year after payment
Compare the original IL-1040, any revised federal return or IRS notice, supporting schedules and payment evidence first.
Frequently Asked Questions
Where can I find my IL-1040 form?
Use IDOR's Individual Income Tax Forms page. Select the correct year and download the form with its instructions.
How do I pay my Illinois state income tax online?
Use IDOR's MyTax or Illinois E-Pay. Choose the correct tax year and payment type, then save the confirmation.
When do I file a tax return for 2027?
Income earned in 2027 is reported on a return filed in the following filing season. Verify the official deadline with IDOR before filing.
What is the Illinois personal income tax rate?
The statutory rate is 4.95% of net income. Confirm the 2027 rate in the latest instructions. Your liability also depends on exemptions, additions, subtractions, credits and payments.
Do I have to file Illinois taxes if I don't owe?
Possibly. Income, residency or Illinois-source income can trigger a filing duty even at a zero balance. Filing may also recover withholding or claim credits.
What is a 1040 form?
Form 1040 is the federal individual return filed with the IRS. IL-1040 is filed with Illinois, and your federal AGI feeds into it.
