2210-K: Underpayment of Estimated Tax By Individuals (2025)

Who files this form

Use Form 2210-K to determine whether you owe a penalty for underpaying Kentucky estimated tax for 2025.

In general, you may owe a penalty if you owe more than $500 and your withholding plus timely estimated payments did not equal at least the smaller of:

• 90% of your 2025 tax, or
• 100% of your 2024 tax. Your 2024 return must cover a full 12 months.

Special rules apply:

• Farmers and fishermen: If at least two-thirds of your Kentucky gross income for 2024 or 2025 came from farming and fishing, substitute 66⅔% for 90%.
• Higher-income taxpayers: Substitute 110% for 100% if your 2024 Kentucky adjusted gross income exceeded $150,000, or $75,000 if your 2024 Kentucky filing status was married filing separately on a combined return or separate returns.

Check Part I for penalty exceptions. Part II, line 5 specifically says to stop and not file Form 2210-K if the amount on that line is $500 or less.

When it's due

For tax year 2025, the form lists these estimated tax payment due dates:

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

For the 2025 farming exception in Part I, qualifying taxpayers must file their return and pay the total tax due by March 2, 2026. The instructions also list March 2, 2026 as the full-payment deadline for the farming or fishing exception.

The final penalty calculation date shown for tax year 2025 is April 15, 2026. The form uses the actual payment date instead if payment was made earlier.

What you'll need

Have these returns and amounts available:

• Your 2025 Form 740, 740-NP, or 741, including your tax liability, withholding, refundable credits, and any nonresident withholding.
• Your 2024 Kentucky return, including your tax liability, adjusted gross income, and filing status.
• The amounts and dates of your estimated tax payments, plus any credit carried forward from a prior-year return.
• Your name and Social Security number or federal identification number as shown on your return.

If claiming a farming or fishing exception, you will need total gross income and farming or fishing income for the qualifying year.

If using the annualized income installment method, have income, adjustments, and any itemized deductions for each period listed in Part III. Include your share of partnership or S corporation income or loss for each period.

How to file

Enclose Form 2210-K with Form 740, 740-NP, or 741.

1. Review Part I. If an exception applies, check the appropriate box, complete the related lines, and check the “Form 2210-K attached” box on Form 740 or 740-NP, line 34(a), or Form 741, line 22(a).
2. If no exception applies, complete Part II to calculate your required annual payment and any underpayment penalty. Complete Part III if using the annualized income installment method.
3. Enter the total penalty from line 23 on Form 740 or 740-NP, line 34(a), or Form 741, line 22(a).

The supplied text does not give a mailing address or e-filing instructions.

Common mistakes

• Including excluded payments in the prepaid-tax exception: The Part I footnote says not to include amounts prepaid with an extension after the fourth declaration installment due date or amounts paid with the original return.
• Working across columns too soon: Complete Part II, lines 11 through 18 for one column before moving to the next.
• Using annualization for only some installments: If you use Part III for any payment due date, you must use it for all payment due dates.
• Using individual annualization periods for estates and trusts: For 2025, estates and trusts must use period ending dates of February 28, April 30, July 31, and November 30 instead of the dates shown for individuals. They also must not use the printed Part III, line 2 annualization amounts.

Questions people ask

Can uneven income reduce my required installments?

Yes. If your income varied during the year, Part III's annualized income installment method may lower or eliminate one or more required installments. The instructions give seasonal business income and a large capital gain late in the year as examples.

How do I allocate withholding and a prior-year credit?

For Part II, line 10, enter 25% of your total Kentucky withholding in each column. Enter the entire credit carried forward from a prior-year return in column A only.

What rates apply to the penalty calculation?

The instructions specify 10% for calendar year 2025 and 9% for calendar year 2026. The required third installment's penalty calculation may use two different rates.

Are there exceptions for estates and trusts?

Yes. Part I lists exceptions for a decedent's estate, or a trust owned by a decedent, for a tax year ending before the date that is two years after the decedent's death.

Official sources

• https://revenue.ky.gov/Forms/2210-K%20(2025).pdf