Schedule 80/20: Related-Party Expenses (2025)
Illinois · Illinois DOR · Used for tax years 2025
Illinois Schedule 80/20 reports related-party expenses and calculates addition and subtraction modifications for interest, intangible expenses, and related income involving affiliated companies. It attaches to Form IL-1120, IL-1120-ST, IL-1065, or IL-1041.
Who files this form
Schedule 80/20 reports related-party expenses and calculates addition and subtraction modifications involving affiliated companies. The form directs you to attach it to Form IL-1120, IL-1120-ST, IL-1065, or IL-1041.
The 2025 version applies to tax years ending on or after December 31, 2025. The form does not provide complete rules for who must file.
All taxpayers may complete Step 2. Steps 3 and 4 may be completed if an addition modification was figured in Step 2.
What you'll need
Have the information requested on the form ready:
- Your name as shown on your Illinois tax return, your federal employer identification number (FEIN), and your tax year-ending month and year.
- Each affiliated company's name and FEIN, and whether it is newly added.
- Interest and intangible expenses paid to each affiliated company, including amounts exempt from add-back.
- Dividends, interest, and intangible income received from each affiliated company, as needed for the calculations.
If you are an affiliated company completing Lines 16 through 22, you also need the paying U.S. company's name and FEIN, the interest and intangible income you received from it, and the amounts from that company's Schedule 80/20, Lines 5 and 8.
How to file
Attach Schedule 80/20 to your Form IL-1120, IL-1120-ST, IL-1065, or IL-1041.
If you have more affiliated companies than the form has space for, complete and attach additional Schedules 80/20. Report Column D totals only on the last additional schedule.
If you attach multiple copies, complete Page 2 only once and attach it as the last page of Schedule 80/20.
The supplied form does not provide a mailing address or e-file instructions.
Common mistakes
- Repeating Page 2 when using multiple schedules. Complete that page once and attach it last. The form warns that failing to do so may delay processing.
- Putting totals on each additional schedule. Report Column D totals only on the last additional Schedule 80/20.
- Entering negative results where zero is required. If Line 5 is negative, enter zero there and enter the result as a positive amount on Line 7. If Line 8 is negative, enter zero.
- Completing the wrong lines in Step 4. If you are not an affiliated company, skip Lines 16 through 22 and complete Line 23. If you are an affiliated company, complete Lines 16 through 22 and Line 23.
- Leaving required information undisclosed. The form warns that failure to provide required information could result in a penalty.
Questions people ask
What if I have more affiliated companies than the form has room for?
Complete and attach additional Schedules 80/20. Report Column D totals only on the last additional schedule, and complete Page 2 once as the last page.
Can I check more than one exemption reason on Line 6c?
Yes. The form allows multiple boxes. The listed reasons are “Paid to unrelated party,” “Add-back unreasonable,” and “Alternative apportionment.” It refers you to instructions for details, but no instructions were supplied here.
How do I calculate the total addition modification?
Add Lines 5 and 8 and enter the total on Line 9.
How do I calculate the total subtraction modification?
Carry Line 14 to Line 15, then add Lines 15, 19, and 22 on Line 23. If you are not an affiliated company, the form tells you to skip Lines 16 through 22 and complete Line 23.