If you did not pay enough Delaware state income tax throughout the year, you may owe an underpayment penalty. Delaware uses Form PIT-UND (Underpayment of Estimated Taxes) to determine whether a penalty applies and, if so, calculate the amount owed.
What Is an Underpayment of Estimated Taxes?
Delaware income tax is generally expected to be paid as income is earned. This can be done through:
- Tax withholding from wages, pensions, or other income
- Quarterly estimated tax payments
- Certain payments made on your behalf, such as S corporation payments
If you do not pay enough tax during the year, Delaware may assess an underpayment penalty even if you pay your full tax balance when filing your return.
Who May Need Form PIT-UND?
You will usually be penalized if you did not pay at least the smaller of:
- 90% of your current year Delaware tax liability, or
- 100% of of your prior year tax liability. If your prior year AGI was greater than $150,000, you must use 110% of your prior year tax liability.
The Delaware Division of Revenue uses Form PIT-UND to determine whether a penalty is due based on the timing and amount of your tax payments throughout the year.
Are there Exceptions to the Penalty?
Yes, exceptions to the penalty exist. You will not have to pay the penalty if any of the following apply:
- You had no Delaware tax liability on your previous year's return.
- For the current year, the required annual payment is less than or equal to $800 (use the Form PIT-UND instructions to determine your required annual payment).
- You were a part-year resident during the tax year, or
- You derived at least 2/3 of your Gross Income from farming or fishing, and paid the total estimated tax due by January 15, 2026, or filed your return by March 1, 2026 AND paid the total tax due at that time.
Program Entry
To complete Form PIT-UND, go to:
- State
- Edit Delaware using the three dots
- Miscellaneous Forms
- Underpayment of Estimated Taxes, Form PIT-UND
You will need to manually enter your Prior tax liability less credits. If your underpayment was made prior to April 30th, enter the number of days between when your payment was made and April 30th.
Important
- Form PIT-UND is used to calculate an underpayment penalty, not additional tax.
- Paying your tax balance when you file will not eliminate an underpayment penalty if tax payments were not made timely during the year.
- Keep records of all Delaware tax payments in case the Division of Revenue requests supporting documentation.
Note: Most taxpayers who have adequate withholding throughout the year will not need to take any additional action regarding Form PIT-UND.