General Information

If you were

Note: Even if you are not required to file Form IL‑1040, you must file to get a refund of

• Illinois Income Tax withheld from your pay,
• estimated tax payments you made, or
• withholding on income passed through to you by a partnership, S Corporation, or trust.

You are an Illinois resident if you were domiciled in Illinois for the entire tax year. Your domicile is the place where you reside and the place where you intend to return after temporary absences. Temporary absences may include duty in the U.S. Armed Forces, residence in a foreign country, out-of-state residence as a student, or out-of-state residence during the winter or summer.

If you filed a joint federal return and one spouse is an Illinois resident while the other spouse is a nonresident or a part-year resident, you may file separate Illinois returns. If you file a joint Illinois return, you will both be taxed as residents.

Your Illinois income includes the adjusted gross income (AGI) amount figured on your federal return, plus any additional income that must be added to your AGI. Note: Some of your income may be subtracted when figuring your Illinois base income. For more information, see the Step-by-Step Instructions.

You should follow the federal law concerning passive activity income and losses. You are not allowed to refigure your federal passive activity losses.

Also, federal law will govern the taxation of income from community property sources in the case of spouses who file joint federal returns and who file separate Illinois returns.

File your individual income tax return electronically by using

• MyTax Illinois, available on our website for free,
• a tax professional, or
• tax preparation software.

Almost all taxpayers can file electronically. Visit mytax.illinois.gov or see your tax professional. If you do not wish to file electronically, you may use the paper Form IL-1040.

Your Illinois filing period is the same as your federal filing period. We will assume that you are filing your Form IL-1040 for calendar year 2023 unless you are filing for a fiscal year and indicate a different filing period in the space provided at the top of the return. The due date for calendar year filers is April 15. If this date falls on a weekend or holiday, then the due date is the next business day after the weekend or holiday.

We grant an automatic six-month extension of time to file your return. If you receive a federal extension of more than six months, you are automatically allowed that extension for Illinois. These extensions do not grant you an extension of time to pay any tax you owe. If you determine that you will owe tax, you must use Form IL-505-I, Automatic Extension Payment for Individuals, to pay any tax you owe to avoid penalty and interest on tax not paid by April 15, 2024.

You must round cents to whole dollars on Form IL-1040 and most schedules, as directed. To round you must

• drop amounts under 50 cents and
• increase amounts of 50 to 99 cents to the next dollar.

For example, $1.49 becomes $1 and $2.50 becomes $3.

If you have to add two or more amounts to figure the amount to enter on a line, include cents when adding the amounts and round only the total.

You will owe

• a late-filing penalty if you do not file a return that we can process by the extended due date.
• a late-payment penalty for tax not paid by the original due date of the return.
• a late-payment penalty for underpayment of estimated tax if you were required to make estimated tax payments and failed to pay the required amount by the payment due dates.
• a bad check penalty if your remittance is not honored by your financial institution.
• a cost of collection fee if you do not pay the amount you owe within 30 days of the date printed on any IDOR-2-BILL, Final Notice of Tax Due for Form IL-1040, Individual Income Tax Return, you receive
• a frivolous return penalty if you file a return that does not contain information necessary to figure the correct tax or shows a substantially incorrect tax, because you are taking a frivolous position or are trying to delay or interfere with collection of the tax.
• interest on unpaid tax from the day after the original due date of your return through the date you pay the tax.

We will bill you for penalties and interest. For more information about penalties and interest, see Publication 103, Penalties and Interest for Illinois Taxes.

If you cannot pay the tax you owe but you can complete your return on time, file your return by the due date without the payment. This will prevent a late-filing penalty from being assessed. You will, however, owe a late-payment penalty and interest on any tax you owe after the original due date, even if you have an extension of time to file.

You have the option to pay the amount you owe electronically by using our website or by credit card. See the instructions for Line 40.

Do not file another Form IL-1040 to make changes to a previously filed Form IL-1040. You must file Form IL-1040-X, Amended Individual Income Tax Return, if

• you discover that you made an error on your Illinois return after it was filed, or
• your federal return has been adjusted either by the Internal Revenue Service (IRS) or on a federal Form 1040X, Amended U.S. Individual Income Tax Return, you filed; the change affects your Illinois income, additions, subtractions, exemptions, or credits; and the change is final.

For more information, see Form IL-1040-X and Instructions.

You may use Form IL-1040 to pay your household employees’ Illinois withholding. For more details on how to pay withholding for your employees, see the instructions for Line 20.

If you change your address after you file, visit our website or call us to tell us your new address and the date you moved.

If you are married and you filed a joint federal return with your spouse and you are an injured spouse (e.g., your spouse owes a liability, for which you are not responsible, to a government agency), you may elect to file separate Illinois returns using the “married filing separately” filing status. You may make this election up until the extended due date of your return, and once the election is made, it is irrevocable for the tax year.

If you participated in a reportable transaction, including a “listed transaction,” during this tax year and were required to disclose that to the IRS, you are also required to disclose that information to Illinois.

You must send us two copies of the form you used to disclose the transaction to the IRS. You must

• attach one copy to your tax return, and
• mail a second copy to the Illinois Department of Revenue,
  P.O. Box 19029, Springfield, Illinois 62794-9029.