IL-1120-ST: Small Business Corporation Replacement Tax Return (2024)
Illinois · Illinois DOR · Used for tax years 2024
Form IL-1120-ST is the Illinois Small Business Corporation Replacement Tax Return. It reports income or loss, Illinois adjustments, replacement tax, and any applicable surcharges, pass-through withholding, and pass-through entity tax. It also calculates your refund or balance due
When it's due
For the 2024 Form IL-1120-ST, the return is due on or before the 15th day of the 3rd month following the close of the tax year.
This version is for tax years ending on or after December 31, 2024, and before December 31, 2025. If your return is not for calendar year 2024, enter your fiscal tax year's beginning and ending dates.
What you'll need
Have your business identification details ready, including your legal name, mailing address, FEIN, NAICS code, Illinois corporate file number, and the location of your accounting records. You will also need income and expense figures from federal Schedule K and Form 1120-S, plus payment and withholding amounts.
Depending on the entries you make, the form calls for these attachments:
- Income adjustments: Form IL-4562, Schedule 80/20, Illinois Schedule M for businesses, Schedule 1299-A, and Schedule(s) K-1-P or K-1-T.
- Shareholder information and pass-through withholding: Schedule B. Its directions require completing Schedule(s) K-1-P and Schedule(s) K-1-P(3) or K-1-P(4) before completing Schedule B.
- Unitary business group reporting: Schedule UB.
- Nonbusiness income: Schedule NB.
- Loss deductions and debt adjustments: Schedule NLD and federal Form 982, as applicable. Attach a detailed statement if you have merged losses.
- Investment credits or credit recapture: Form IL-477 or Schedule 4255.
- Illinois income tax withholding: Form(s) W-2G.
- Certain federal reporting: Federal Form 8886 or federal Schedule M-3, Part II, Line 10, if completed.
- Annualized income for pass-through entity tax: Form IL-2220 if you are paying that tax and annualized your income on that form.
If enclosing a payment, attach the payment and Form IL-1120-ST-V in the space shown on page 1.
How to file
Complete the applicable steps and attachments. An authorized officer must sign and date the return and provide their title and phone number.
If a payment is enclosed, mail the return to:
Illinois Department of Revenue
P.O. Box 19053
Springfield, IL 62794-9053
If a payment is not enclosed, mail the return to:
Illinois Department of Revenue
P.O. Box 19032
Springfield, IL 62794-9032
Enter your payment amount in the space at the top of page 1. Attach your payment and Form IL-1120-ST-V where indicated.
The supplied text does not provide e-filing directions.
Common mistakes
- Completing the wrong allocation section: If your Line 35 amount is derived only inside Illinois and you are not a unitary filer, check Line A, carry Line 35 to Line 47, and leave Step 6 blank. If any portion is derived outside Illinois, or you are a unitary filer, check Line B and complete every line of Step 6. Do not leave Lines 40 through 42 blank.
- Entering invalid sales figures: Lines 40 and 41 cannot be negative. Round the Line 42 apportionment factor to six decimal places.
- Missing the business income election entries: If you elect to treat all nonbusiness income as business income, check Step 1, Box S, and enter zero on Lines 36 and 44.
- Completing Schedule B out of order: Complete the required K-1 schedules and Schedule B, Section B, before Section A. The form warns that failing to follow its directions may delay processing or lead to requests for more information.
- Leaving out extra Schedule B pages: Attach all Section B pages behind Section A. Use additional copies of Section B if you need more space for shareholders.
- Omitting a carryforward explanation: If an overpayment carryforward is going to a different FEIN, check the box at Line 68 and attach a detailed statement.
Questions people ask
What replacement tax rate does the form use?
Line 52 calculates replacement tax by multiplying net income on Line 51 by 1.5% (.015).
Can I have my refund directly deposited?
Yes. Complete Line 70 with your routing number and account number, and select checking or savings.
What should I enter for a final return?
Check the final return box in Step 1 and enter the termination date. If the return is final because you sold the business, also enter the sale date and the new owner's FEIN.
How do I show that I elected pass-through entity tax?
Check Step 1, Box L. If you are paying pass-through entity tax and annualized your income on Form IL-2220, also check Box M and attach Form IL-2220.