In TurboTax, in the Wisconsin state income tax return, at the screen Underpayment Interest, the Schedule U is discussed.
At this screen, you may allow the Wisconsin Department of Revenue to ca...
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In TurboTax, in the Wisconsin state income tax return, at the screen Underpayment Interest, the Schedule U is discussed.
At this screen, you may allow the Wisconsin Department of Revenue to calculate interest on an underpayment of estimated tax or you may see whether you meet an exception to the underpayment interest.
Wisconsin Department of Revenue Schedule U Underpayment of Estimated Tax by Individuals, Partnerships, and Fiduciaries may be found here.
Wisconsin Schedule U Instructions states:
Purpose of Schedule U
Use Schedule U to see if you owe interest for underpaying your estimated tax and, if you do, to figure the amount of interest you owe. It may be used by individuals, partnerships, estates, and trusts (except trusts subject to the Wisconsin tax on unrelated business income must use Form U, Underpayment of Estimated Tax by Corporations).
Who Must Pay Underpayment Interest
If you did not pay enough estimated tax by any due date, or if you did not have enough Wisconsin income tax withheld, you may be charged interest on the underpayment. This is true even if you have a refund when you file your tax return. Underpayment interest is figured separately for each due date. Therefore, you may owe underpayment interest for an earlier payment due date, even if you pay enough tax later to make up the underpayment.
In general, you may owe underpayment interest for 2025 if you did not pay at least the smaller of:
90% of your current year (2025) tax liability, or
100% of your prior year (2024) tax liability if you filed a 2024 return that covered a full 12 months.
Note: The alternative to pay 100% of prior year tax liability does not apply to an estate or trust with taxable income of $20,000 or more.