IL-1065-X: Amended Partnership Replacement Tax Return (2025)
Illinois · Illinois DOR · Used for tax years 2025
Form IL-1065-X is Illinois's Amended Partnership Replacement Tax Return for tax years ending on or after December 31, 2025. It reports corrected income, deductions, replacement tax, withholding, and pass-through entity tax, and calculates any refund or additional tax due.
Who files this form
Form IL-1065-X is for partnerships amending an Illinois Partnership Replacement Tax Return.
The 2025 version is for tax years ending on or after December 31, 2025. Enter the beginning and ending dates of the tax year you are amending. Do not use this version for a tax year ending before December 31, 2025.
What you'll need
Have your partnership’s legal name, mailing address, FEIN, NAICS code, and amounts as most recently reported or adjusted, along with the corrected amounts. The income calculations refer to federal Form 1065 and federal Schedule K.
Attach supporting documents that apply to your changes:
- Federal finalization documentation for a federal change.
- Schedule UB if you are included in a unitary business group’s combined apportionment schedule.
- Federal Form 8886 and federal Schedule M-3, Part II, Line 10, if completed and not previously attached.
- Forms IL-4562 and IL-477, and Schedules 80/20, M, F, 1299-A, NB, NLD, and 4255, as required by the lines you complete.
- Schedule B for the partner income, loss, and withholding amounts identified on the return.
- Schedules K-1-P or K-1-T for distributive additions, subtractions, or pass-through withholding reported to you.
- Forms W-2G for Illinois income tax withholding.
- Form IL-2220 if you are paying PTE tax and annualized your income on that form.
- A detailed statement for merged losses or an overpayment carryforward going to a different FEIN.
Investment partnerships should attach documentation supporting their investment partnership status.
How to file
- Identify your partnership and the tax year being amended. Check the applicable type-of-change box and explain the changes. Attach a separate explanation sheet if needed.
- Enter amounts as most recently reported or adjusted in Column A and corrected amounts in Column B. Use whole dollars where indicated.
- Complete the applicable calculations and attach the required forms and schedules.
- Have a partner sign and date the return, and provide their title and phone number.
- If paying with the return, enter the payment amount at the top of Page 1 and attach your payment and Form IL-1065-X-V in the space provided.
Mail the return to:
Illinois Department of Revenue
P.O. Box 19016
Springfield, IL 62794-9016
Common mistakes
- Using the wrong year’s form: Do not use this version for tax years ending before December 31, 2025.
- Completing Step 6 incorrectly: If income is derived only inside Illinois and you are not a unitary filer, check Line A and leave Step 6 blank. If any income 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.
- 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 these instructions may delay processing or lead to requests for more information.
- Leaving out member information: Attach additional copies of Schedule B, Section B, if you have more members than the page allows.
- Forgetting the payment entry: Enter the amount paid with the return at the top of Page 1.
Questions people ask
What if I am amending only to report a larger net loss?
Check the box in Step 1, Item C, if you are filing only to report an increased net loss on Line 47, Column B.
Does an investment partnership complete the replacement tax calculation?
No. The form says investment partnerships should skip Step 8, which calculates net replacement tax.
Can I apply an overpayment forward instead of receiving it all as a refund?
Line 70 provides a space for the amount of your overpayment to be credited forward. Line 71 shows the remaining amount to be refunded. If the carryforward goes to a different FEIN, check the box and attach a detailed statement.
How will additional penalties and interest be handled?
The form states that you will be sent a bill for any additional penalty and interest.