ScheduleU: ScheduleU (2025)

Who files this form

Wisconsin Schedule U is used by individuals, partnerships, and fiduciaries to figure underpayment interest on estimated tax for 2025. Include it with Wisconsin Form 1, 1NPR, 2, or 3.

Start with Part I, which all filers must complete. The form gives these exceptions:

• If line 3, net tax minus other credits, is zero or less, do not complete or file Schedule U.
• If line 6, line 3 minus Wisconsin tax withheld, is less than $500, do not complete or file Schedule U.

When it's due

For tax year 2025, the estimated tax installment due dates for calendar-year taxpayers are:

• April 15, 2025
• June 16, 2025
• September 15, 2025
• January 15, 2026

The form says to adjust these dates for fiscal-year returns.

April 15, 2026 is also used in the 2025 underpayment interest calculation. Under the regular method, line 26 counts days through the date the balance due on the tax return was paid or April 15, 2026, whichever is earlier. This is not stated as a separate Schedule U filing deadline.

What you'll need

Have the information requested by the form ready:

• Your legal name and identifying number as shown on your tax return.
• Your 2025 Wisconsin return: Form 1, 1NPR, 2, or 3, including net tax and other credits.
• Your prior-year 2024 tax amount.
• Your Wisconsin tax withheld for 2025.
• The amounts and dates of estimated tax payments and any payment of the balance due on your return.

If you use the annualized income installment method, you will also need Wisconsin income for each period shown in Part IV, plus the applicable deductions, exemptions, and credits.

How to file

Include Schedule U with Wisconsin Form 1, 1NPR, 2, or 3. The supplied form does not give a mailing address or e-filing directions.

Complete Part I first. Then choose the applicable calculation method:

• Short method, Part II: You may use this if you made no estimated tax payments, or if you made four equal estimated tax payments on the due dates.
• Regular method, Part III: Use this otherwise.
• Annualized income installment method, Part IV: Complete lines 30 through 50 only if using this method to calculate installments.

Transfer the underpayment interest from line 15 or line 29 to Form 1, line 44; Form 1NPR, line 74; Form 2, line 24; or Form 3, line 3. Increase the amount you owe or decrease your refund accordingly.

Common mistakes

Watch for these cautions and reminders printed on the form:

• Do not use the calendar-year installment dates or annualization period dates unchanged for a fiscal-year return. Adjust them accordingly.
• In Part IV, complete one column through line 50 before starting the next column.
• If you use Part IV to calculate any column of line 16, use it for all four columns.
• The total of the amounts on Part IV, line 50 should equal Part I, line 8.
• Estates and trusts must use the substitute period-ending dates and annualization amounts printed for them, not the standard ones shown in the worksheet.

Questions people ask

Can I use the short method?

Yes, if you made no estimated tax payments or made four equal estimated tax payments on the due dates. Otherwise, use the regular method in Part III.

What if line 12 is zero or less?

Stop there. The form says you do not owe underpayment interest.

How is the required annual payment calculated?

Part I directs you to enter the smaller of line 4 or line 7 on line 8. Line 4 is 90% of line 3, and line 7 is your prior-year 2024 tax. The form refers to instructions for these entries, but those instructions were not supplied.

Can I use the annualized income worksheet for just one installment?

No. If you use the worksheet to calculate any column of line 16, the form requires you to use it for all four columns.

Does underpayment interest affect my refund?

Yes. The form tells you to transfer the interest to your Wisconsin return and either increase the amount you owe or decrease your refund.

Official sources

• https://www.revenue.wi.gov/TaxForms2025/2025-ScheduleU.pdf