PIT-UND: Underpayment of Estimated Taxes (2025)
Delaware · Delaware Division of Revenue · Used for tax years 2025
Delaware Form PIT-UND calculates underpayments of estimated tax and any resulting penalty for 2025. It includes calculations for the required annual payment, a short method, and an annualized installment method.
When it's due
For tax year 2025, Part 5 lists these estimated payment due dates:
- May 1, 2025
- June 16, 2025
- September 15, 2025
- January 15, 2026
What you'll need
Have these returns and payment details available to complete the form:
- Your 2025 Delaware return: Form PIT-RES or PIT-NON, for your tax liability and other figures used in the calculation.
- Your 2024 Delaware return: For the prior-year tax liability calculation in Part 1.
- Delaware withholding and payment details: Estimated tax payments, S corporation payments, refundable business credits, and any capital gain tax payments used in Part 4.
- Payment dates: Part 5 uses the number of days between the listed due date and when payment was made.
If using the annualized installment method, you also need income and deduction amounts for each period printed in Part 3, along with the applicable credits and tax table or tax schedule.
Common mistakes
- Do not continue past the Part 1 stopping rule: If Line C minus Line D is $800 or less, stop. The form says you do not owe the penalty.
- Do not continue the short method if there is no underpayment: If Line I is zero or less, stop.
- Do not enter both standard and itemized deductions in Part 3: Enter zero on Line 5 if you did not itemize, and zero on Line 8 if you itemized.
- Remember the nonresident checkbox: Check the box on page 2 if you used a nonresident return.
Questions people ask
How is the required annual payment calculated?
Part 1 compares 90% of your 2025 Delaware tax liability with 100% or 110% of your 2024 Delaware tax liability. The smaller amount goes on Line C. The form refers to instructions for choosing between 100% and 110%, but those instructions were not provided.
When does the form say I do not owe a penalty?
Part 1 says to subtract Delaware withholding on Line D from the required annual amount on Line C. If the result is $800 or less, stop. You do not owe the penalty.
Does the form include an annualized installment method?
Yes. Part 3 provides an annualized installment calculation using income and deductions for the periods printed on the form. Page 1 also has a checkbox for taxpayers using the annualization of income method.
How does Part 5 calculate the penalty?
For each column, enter the number of days from the listed payment due date to when payment was made. Multiply those days by 0.05% (0.0005), then multiply that result by the underpayment on Line 37. Add the penalties from all columns to get the total penalty.