FormC: FormC (2025)
Wisconsin · Wisconsin DOR · Used for tax years 2025
Wisconsin Form C reports income and expenses allocated to Wisconsin and outside Wisconsin. It reconciles book income or net income per income statement with net income and collects information about separate accounting, branch transfers, and allocation methods.
What you'll need
Have these records and forms available to complete Form C:
- Your name and federal employer identification number.
- Records of income and expenses allocated to Wisconsin and outside Wisconsin, including the basis for allocation.
- Federal Schedule M-1 or, for Schedule M-3 filers, the income statement and addition and subtraction adjustments from Schedule M-3, Parts II and III.
- The additions and subtractions reported on your applicable Wisconsin Form 3, 4, 4T, 5S, or 6 and its schedules.
- Records of transfers between Wisconsin and out-of-state branches, including sales, purchases, management fees paid, interest paid, and royalties paid.
Attach an explanation of how transfer prices were determined.
How to file
File Form C with Wisconsin Form 3, 4, 4T, 5S, or 6.
- Complete Part I to show income and expenses allocated to Wisconsin, allocated outside Wisconsin, and in total. Include the basis of allocation.
- Complete Part II to reconcile book income or net income per income statement with net income.
- From line 16, enter column 1 on Form N, line 6, column a, and column 3 on Form N, line 6, column b.
- Answer the question about written permission to use separate accounting, report branch transfers, and explain how income and expenses were allocated in and outside Wisconsin.
- Attach an explanation of how transfer prices were determined.
Common mistakes
- Using a book income total that does not match the federal figures. Part I, line 5, column 3 must agree with federal Schedule M-1, line 1, or, for Schedule M-3 filers, net income per income statement figured on a separate company basis.
- Entering a different starting amount in Part II. Line 6 must agree with Part I, line 5.
- Leaving out the transfer-pricing explanation. The form requires an attached explanation of how transfer prices were determined.
Questions people ask
What is Form C called?
Its title is “Wisconsin Allocation and Separate Accounting Data.”
Which Wisconsin return do I file it with?
File it with Wisconsin Form 3, 4, 4T, 5S, or 6.
Where do I report income that will be apportioned instead of allocated?
On line 15, enter the amount from line 14 that will be apportioned instead of allocated. Line 16 subtracts that amount from line 14 to determine allocable net income.
Does Form C ask about permission to use separate accounting?
Yes. Line 17 asks whether the taxpayer has obtained written permission from the Department of Revenue to use separate accounting. Check Yes or No.
Do I need to explain how income and expenses were allocated?
Yes. Line 19 asks you to explain how income and expenses were allocated in and outside Wisconsin.