Form1CNS: Form1CNS (2025)
Wisconsin · Wisconsin DOR · Used for tax years 2025
Wisconsin Form 1CNS is a composite individual income tax return for qualifying and participating nonresident shareholders of a tax-option (S) corporation. It reports their Wisconsin income or loss, tax, withholding, and the resulting amount due or refund.
Who files this form
Form 1CNS is a composite Wisconsin individual income tax return for qualifying and participating nonresident shareholders of a tax-option (S) corporation.
Only qualifying shareholders may be included. The form refers to the instructions for eligibility details, but those instructions were not provided. The corporation must have a power of attorney or other written authorization from each participating shareholder to file on their behalf.
When it's due
The printed due date for the 2025 tax year return is April 15, 2026.
What you'll need
Gather the information and authorizations requested on the form:
- The corporation’s name, address, federal employer ID number, year ending, and contact information.
- Each participating shareholder’s name, address, Social Security number, ownership percentage, filing status, and Wisconsin income information.
- Federal adjusted gross income from Form 1040, Wisconsin gross income from Schedule 5K-1, line 20, and tax withheld from Form PW-1.
- A power of attorney or other written authorization from each qualifying and participating shareholder.
Include a copy of any application for a federal filing extension. For an amended return, include Schedule AR. Attach a separate shareholder schedule if necessary.
Do not attach federal Form 1120S, Wisconsin Form 5S, Wisconsin Form PW-1, federal Schedules K-1, or Wisconsin Schedules 5K-1.
How to file
The supplied form is marked “Sample Form File Electronically.” It directs filers to “Filing Methods” in the instructions for filing details. Those instructions were not provided, and the form does not print a mailing address or detailed electronic filing steps.
Common mistakes
- Including shareholders who do not qualify. The form cautions that only qualifying shareholders may be included.
- Attaching documents the form says not to attach. Do not attach federal Form 1120S, Wisconsin Form 5S, Wisconsin Form PW-1, federal Schedules K-1, or Wisconsin Schedules 5K-1.
- Leaving out an extension application copy. Include a copy of any application for a federal extension of time to file.
- Omitting Schedule AR on an amended return. Check the amended-return box and include Schedule AR.
- Failing to mark a final return. Check the final-return box if this is a final return.
Questions people ask
Who receives an overpayment refund?
The form says the overpayment on Schedule 1, line 9, is refunded to the corporation.
Does the corporation need authorization from shareholders?
Yes. The signature declaration states that the corporation has a power of attorney or other written authorization from each qualifying and participating nonresident shareholder.
What if there is not enough room to list all participating shareholders?
Schedule 2 allows a separate schedule to be attached if necessary.
Can another person discuss the return with the department?
Yes. The third-party designee section lets you select “Yes” and enter the designee’s name, phone number, and personal identification number (PIN).