IL-1120: Corporation Income and Replacement Tax Return (2025)
Illinois · Illinois DOR · Used for tax years 2025
Form IL-1120 is the 2025 Illinois Corporation Income and Replacement Tax Return. It reports a corporation’s income or loss, Illinois adjustments, taxes, credits, and payments to determine a refund or balance due.
What you'll need
Attach federal Form 1120, pages 1 through 6, or an equivalent federal return.
Have your corporation’s legal name, mailing address, FEIN, NAICS code, corporate file number, and accounting-records location ready.
Other attachments depend on the entries you complete. These include:
- Group or foreign insurer filings: Schedule UB/Subgroup Schedule, Schedule INS, or Schedule UB/INS, as applicable.
- Income adjustments: Form IL-4562, Schedule 80/20, Schedule M and its required support, Schedule 1299-B and its required support, or Schedule NB, as applicable.
- Foreign dividend subtraction: Illinois Schedule J and federal Form 1120, Schedule C, or equivalent.
- Pass-through amounts: Schedules K-1-P or K-1-T for applicable income, additions, subtractions, withholding, or pass-through entity tax credits.
- Losses and debt adjustments: Schedule NLD or UB/NLD for the Illinois net loss deduction; federal Form 982 for a discharge of indebtedness adjustment. Attach a detailed statement if you have merged losses.
- Credits and penalties: Schedule 4255, Form IL-477 and required support, Schedule 1299-D and required support, or Form IL-2220, as applicable.
- Illinois income tax withholding: Copies of all Forms W-2G.
- Other applicable attachments: Federal Form 8886, federal Schedule M-3, and Schedule INL.
Use the attachment checklist on page 4 to match your completed entries to the required documents.
How to file
Complete the applicable steps, attach the required supporting documents, and have an authorized officer sign and date the return.
Mailing without a payment:
ILLINOIS DEPARTMENT OF REVENUE
PO BOX 19048
SPRINGFIELD IL 62794-9048
Mailing with a payment:
ILLINOIS DEPARTMENT OF REVENUE
PO BOX 19038
SPRINGFIELD IL 62794-9038
If you owe tax on Line 67, the form directs you to make an electronic payment at Tax.Illinois.gov. If you must mail your payment, complete Form IL-1120-V. Write your FEIN, tax year ending, and “IL-1120-V” on your check or money order, payable to “Illinois Department of Revenue.” Attach the voucher and payment where indicated on page 1, and enter the payment amount at the top of that page.
Common mistakes
- Missing attachments: The form warns that failure to attach required documents may result in disallowance of the corresponding line item.
- Completing the wrong part of Step 4: If your Line 23 amount is derived only inside Illinois and you are not a unitary filer, check Step 3, box A, carry Line 23 to Line 35, and leave Lines 24 through 34 blank. Unitary filers must not check box A.
- Leaving apportionment entries blank: If any portion of Line 23 is derived outside Illinois, or you are a unitary filer, check Step 3, box B, and complete all lines of Step 4. Do not leave Lines 28 through 30 blank.
- Missing attachment checkboxes: Check the applicable Step 1 boxes for attached schedules and forms, as directed by the page 4 checklist.
- Forgetting the payment amount: Enter the amount paid with the return in the space at the top of page 1.
- Missing a carryforward statement: If an overpayment carryforward is going to a different FEIN, check the box on Line 64 and attach a detailed statement.
Questions people ask
Which tax years does the 2025 form cover?
This form is for tax years ending on or after December 31, 2025, and before December 31, 2026. If your return is not for calendar year 2025, enter your fiscal tax year’s beginning and ending dates on page 1.
What tax rates are printed on the form?
Line 40 calculates replacement tax by multiplying Line 39 net income by 2.5%. Line 45 calculates income tax by multiplying Line 39 by 7.0%. Later lines account for applicable credits, reductions, surcharges, and penalties.
Can I receive my refund by direct deposit?
Yes. Complete Line 66 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, Line C, 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 on Line D.