IL-1120: Corporation Income and Replacement Tax Return (2024)
Illinois · Illinois DOR · Used for tax years 2024
Form IL-1120 is the 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 return.
Other attachments depend on the entries you complete. The checklist on page 4 lists the required documents, including:
- Unitary filers: Schedule UB/Subgroup Schedule. Foreign insurers also have Schedule INS or UB/INS requirements.
- Special depreciation: Form IL-4562.
- Related-party expenses: Schedule 80/20.
- Distributive shares and income from the entities listed on Lines 25 and 33: Schedules K-1-P or K-1-T.
- Other additions or subtractions: Schedule M and its required supporting documents.
- Subtractions on Lines 11 through 15: Schedule 1299-B and its required supporting documents.
- Foreign dividend subtraction: Illinois Schedule J and federal Form 1120, Schedule C, or an equivalent.
- Nonbusiness income or loss: Schedule NB.
- Discharge of indebtedness adjustment: Federal Form 982.
- Illinois net loss deduction: Schedule NLD or UB/NLD. Attach a detailed statement if you have merged losses.
- Investment credit recapture: Schedule 4255. Investment credits require Form IL-477 and its required support; income tax credits require Schedule 1299-D and the specified support.
- Estimated tax underpayment penalty or annualized income: Form IL-2220.
- Pass-through withholding or pass-through entity tax credits: All Schedules K-1-P and K-1-T you received showing those amounts.
- Illinois income tax withholding: Copies of all Forms W-2G.
Attach federal Form 8886 or federal Schedule M-3, as applicable, if you completed the items identified in Step 1, Line F. Attach Schedule INL if you check Step 1, Line V.
If you mail a payment, include Form IL-1120-V.
How to file
Complete the applicable steps, attach the required documents, and have an authorized officer sign the return in Step 9.
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 payment voucher Form IL-1120-V.
- Write your FEIN, tax year ending, and “IL-1120-V” on your check or money order.
- Make it payable to Illinois Department of Revenue.
- Attach the voucher and payment in the space marked on page 1.
- Enter your payment amount at the top of page 1.
Common mistakes
- Missing required attachments: The form warns that missing documents may result in disallowance of the corresponding line item.
- Leaving out required information: The form warns that failure to provide required information could result in a penalty.
- Completing Step 4 when it should be blank: If Line 23 is derived only inside Illinois and you are not a unitary filer, check box A, carry Line 23 to Line 35, and leave Lines 24 through 34 blank.
- Skipping Step 4 for a unitary filer or income derived partly outside Illinois: Check box B and complete every line in Step 4. Do not leave Lines 28 through 30 blank.
- Using negative amounts where prohibited: Lines 2, 28, and 29 cannot be negative.
- Using the wrong rounding: Step 2 calls for whole dollars only. Round the apportionment factor on Line 30 to six decimal places.
- Claiming a net loss deduction when Line 37 is zero or negative: Enter zero on Line 38 in that situation.
Questions people ask
Which tax years does the 2024 form cover?
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 on page 1.
Can I have my refund directly deposited?
Yes. Complete Line 66 with your routing number and account number, and select checking or savings.
What if this is my corporation's 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.
What if I elect to treat all nonbusiness income as business income?
Check the business income election box in Step 1, Line S, and enter zero on Lines 24 and 32.
What if an overpayment carryforward is going to a different FEIN?
Check the box on Line 64 and attach a detailed statement.