Form IL-990-T-X, officially called the Amended Exempt Organization Income and Replacement Tax Return, is issued by the Illinois Department of Revenue (IDOR) and used by tax-exempt organizations to amend previously filed Form IL-990-T returns. This form applies to tax years ending on or after December 31, 2024.
If your organization discovers an error or receives a federal or state adjustment affecting its Illinois return, you must file Form IL-990-T-X to report the corrected information. The form ensures that the state records accurately reflect your corrected income, tax, credits, and payments. You’ll also use it if you receive a federal change notice that impacts your Illinois tax calculation.
Only use this version for tax years ending December 31, 2024, or later; earlier years require older versions. The form also requires clear explanation of the corrections being made, including attached documentation where necessary. It is designed for corporations and trusts that are tax-exempt federally but owe Illinois income and replacement taxes on unrelated business income.
How To File Form IL-990-T-X
You can file Form IL-990-T-X by mailing the completed document to:
Illinois Department of Revenue
P.O. Box 19016, Springfield, IL 62794-9016.
If you owe additional tax (line 38), include your payment with Form IL-990-T-X-V (Payment Voucher). Make the check or money order payable to “Illinois Department of Revenue”, and write your FEIN, tax year ending, and “IL-990-T-X-V” on it. Attach the payment and voucher to the front of Form IL-990-T-X.
If the change results in a refund or credit, you’ll indicate this in Step 6. Attach all supporting schedules, such as federal finalization notices, Schedules K-1, IL-477, or 4255, as required.
How to Complete Form IL-990-T-X
Top Section – General Information
- Tax Year Beginning / Ending:
Enter the beginning and ending dates of the tax year you’re amending. If your tax year ended before December 31, 2024, you must use the earlier form version. - Payment Entry Box:
If you owe tax, write the payment amount you’re submitting on this line.
Step 1: Identify Your Exempt Organization
A. Legal Business Name:
Enter your complete legal name as registered. If your organization’s name has changed, check the box.
B. Mailing Address:
Provide your organization’s current mailing address, including C/O (if applicable), city, state, and ZIP code.
C. Throwback Adjustment:
If applicable, enter your throwback adjustment as directed in the instructions.
D. Double Throwback Adjustment:
If applicable, enter this figure per the official guidance.
E. 52/53-Week Filer Box:
Check this box if your fiscal year is based on a 52/53-week reporting period.
Explain the Changes:
Describe each correction made to your return (e.g., income reclassification, credit adjustment). If more space is needed, attach a separate sheet.
F. Federal Employer Identification Number (FEIN):
Enter your organization’s 9-digit FEIN.
G. Type of Change:
Select whether the amendment is due to a State change or Federal change.
- If Federal, mark whether it’s Partial Agreed or Finalized, and enter the date finalized.
- Attach a copy of your federal finalization notice.
H. Corporation Checkbox:
Mark this if your organization is taxed as a corporation.
I. Trust Checkbox:
Mark this if your organization is taxed as a trust.
J. Schedule 1299-D Checkbox:
Check this if Schedule 1299-D (Income Tax Credits) is attached.
Step 2: Figure Your Base Income Or Loss
Two columns are provided —
Column A: “As most recently reported or adjusted.”
Column B: “Corrected amount.”
Line 1: Unrelated business taxable income or loss from federal Form 990-T.
Line 2: Illinois income, replacement tax, and surcharge deducted when calculating Line 1.
Line 3: Base income or loss — add Lines 1 and 2.
Next, determine whether to complete Step 3:
- Box A: Check if all income is from Illinois or you are a resident trust. Transfer Line 3 to Step 4, Line 12, and leave Step 3 blank.
- Box B: Check if any portion of Line 3 is from outside Illinois. Complete all Step 3 lines (4–11).
Step 3: Figure Your Income Allocable To Illinois
Complete only if you checked Box B in Step 2.
Line 4: Enter business income/loss from non-unitary partnerships, partnerships on a Schedule UB, S corporations, trusts, or estates.
Line 5: Subtract Line 4 from Line 3.
Line 6: Total sales everywhere (cannot be negative).
Line 7: Total sales inside Illinois (cannot be negative).
Line 8: Apportionment factor — divide Line 7 by Line 6; round to six decimals.
Line 9: Multiply Line 5 by Line 8 to find business income or loss apportionable to Illinois.
Line 10: Add income/loss from non-unitary partnerships, S corps, or trusts.
Line 11: Add Lines 9 and 10 → Base income or loss allocable to Illinois.
Step 4: Figure Your Net Replacement Tax
Line 12: Net income or loss from Line 3 (Box A) or Line 11 (Box B).
Line 13: Replacement tax — multiply Line 12 by:
- 2.5% (.025) if taxed as a corporation.
- 1.5% (.015) if taxed as a trust.
Line 14: Recapture of investment credits (attach Schedule 4255).
Line 15: Add Lines 13 + 14 → Replacement tax before credits.
Line 16: Investment credits (attach Form IL-477).
Line 17: Subtract Line 16 from Line 15 → Net replacement tax (enter 0 if negative).
Step 5: Figure Your Net Income Tax
Line 18: Net income/loss from Line 12.
Line 19: Calculate income tax per current rate.
Line 20: Recapture of investment credits (attach Schedule 4255).
Line 21: Add Lines 19 + 20 → Income tax before credits.
Line 22: Income tax credits (attach Schedule 1299-D).
Line 23: Subtract Line 22 from Line 21 → Net income tax (enter 0 if negative).
Step 6: Figure Your Refund Or Balance Due
Line 24: Net replacement tax (from Line 17).
Line 25: Net income tax (from Line 23).
Line 26: Compassionate Use of Medical Cannabis Program Act surcharge (if applicable).
Line 27: Sale of assets by gaming licensee surcharge.
Line 28: Add Lines 24–27 → Total net income, replacement taxes, and surcharges.
Line 29: Payments:
- 29a: Credit from prior year overpayments.
- 29b: Total payments made before this amendment.
- 29c: Pass-through withholding (attach Schedules K-1-P or K-1-T).
- 29d: Pass-through entity tax credit (attach Schedules K-1-P or K-1-T).
- 29e: Illinois income tax withholding (attach Form W-2G).
Line 30: Add Lines 29a–29e → Total payments.
Line 31: Previously paid penalties/interest.
Line 32: Total prior overpayments or refunds for this year.
Line 33: Add Lines 31 + 32.
Line 34: Subtract Line 33 from Line 30 → Net tax paid.
Line 35: Overpayment — if Line 34 > Line 28, subtract Line 28 from 34.
Line 36: Portion of Line 35 to be credited forward (check box if applying to another FEIN).
Line 37: Subtract Line 36 from Line 35 → Refund amount.
Line 38: If Line 28 > Line 34, subtract Line 34 from 28 → Tax due.
If you owe tax, complete Form IL-990-T-X-V and attach your payment. You’ll receive a bill for any extra penalty or interest.
Step 7: Sign Below
- The authorized officer must sign and date the return, listing their title and phone number.
- Paid preparers must complete their section, including printed name, firm name, FEIN, address, phone, and PTIN.
- Check the box to authorize the Illinois Department of Revenue to discuss the return with the preparer.
Final Checklist Before Filing
- Attach all schedules: IL-477, 4255, 1299-D, K-1s, and any federal change documentation.
- Include Form IL-990-T-X-V and payment if tax is due.
- Mail to P.O. Box 19016, Springfield, IL 62794-9016.
- Keep copies of all forms and attachments for your records.