CT-2210: Underpayment of Estimated Income Tax by Individuals, Trusts, and Estates (2024)
Connecticut · Connecticut DRS · Used for tax years 2024
Form CT-2210 is used by individuals, trusts, and estates to calculate interest on underpaid Connecticut estimated income tax for 2024. It determines the required annual payment and calculates underpayments and interest for each calendar quarter.
Who files this form
Form CT-2210 is for individuals, trusts, and estates filing Form CT-1040, CT-1040NR/PY, or CT-1041 who underpaid Connecticut estimated income tax.
File it with your 2024 return if a reason in Part 1 applies. These reasons include:
- Using the annualized income installment method because your income varied during the year.
- Basing payments on your 2023 tax when you filed jointly in either 2023 or 2024, but not both.
- Applying withholding on the dates it was actually withheld rather than in equal installments.
- Qualifying as a farmer or fisherman.
- Being unable to use your prior-year tax liability as the basis for your required annual payment.
- Having no 2023 Connecticut tax liability and not filing a 2023 return, under the residency and income conditions for Box F or G.
You may also file to calculate and pay the interest with your return. Otherwise, DRS will calculate any underpayment interest and send a bill.
If Box F or G applies, check it, stop, and attach Page 1 to your return. When completing Part 2, follow its stop rules: do not complete or file the form if Line 4 is less than $1,000 or Line 7 is zero or less.
When it's due
For tax year 2024:
- The printed general estimated-payment dates are April 15, 2024; June 15, 2024; September 15, 2024; and January 15, 2025. If a due date falls on a Saturday, Sunday, or legal holiday, payment is timely on the next business day. Fiscal-year filers should follow federal filing dates.
- If you file your 2024 return and pay the full amount due by January 31, 2025, you do not have to make the January 15, 2025 estimate and will not owe underpayment interest for the fourth installment.
- Qualifying farmers and fishermen must either pay their single required installment by January 15, 2025, or file their 2024 return and pay the full amount due by March 1, 2025.
- Underpayment interest stops accruing on the earlier of April 15, 2025, or the date the underpayment is paid.
What you'll need
Have the following available, as applicable:
- Your 2024 Connecticut return and your 2023 Connecticut return if using prior-year tax.
- Names and Social Security numbers as shown on your return, including your spouse's information for a joint return. Trusts and estates need the trust or estate name, fiduciary's name, and federal employer identification number.
- Forms W-2, 1099, and Schedule CT K-1 showing Connecticut withholding.
- Schedule CT-PE or Schedule CT-1041 K-1 showing your Pass-Through Entity Tax Credit.
- Amounts and dates of estimated payments, late payments, and actual withholding if using that method.
If you use the annualized income installment method, attach Schedule A and calculations of Connecticut adjusted gross income for each period. Nonresident and part-year resident individuals must also include Worksheet 1. Trusts and estates use Connecticut taxable income for Schedule A.
How to file
- Electronic filing: Select the Form CT-2210 indicator on your Connecticut income tax return. Complete Form CT-2210 and upload it as an attachment.
- Paper filing: Check the Form CT-2210 box on the front of your Connecticut income tax return. Place Form CT-2210 at the back of the completed return.
Include any required schedules and calculations. Enter the total interest from Part 3, Line 17, on the appropriate line of your Connecticut income tax return. Keep copies of the worksheets and schedules for your records.
The supplied text does not provide a mailing address.
Common mistakes
- Using the wrong year's form. Submit the 2024 form for your 2024 return to avoid processing delays.
- Putting other payments in the withholding lines. Do not include estimated payments or taxes withheld for the IRS or other jurisdictions in Connecticut withholding.
- Subtracting payments too early. Part 2, Line 1 is your Connecticut income tax before subtracting estimated payments, PE Tax Credits, or withholding.
- Using annualization for only some installments. If you use that method for any installment, you must use it for all installments and attach the required calculations.
- Missing the return indicator or attachments. Check the Form CT-2210 box or electronic indicator and include the required form pages and schedules.
- Completing Worksheet D unnecessarily. Do not complete it if you file your 2024 return and pay the tax in full by January 31, 2025.
Questions people ask
Can I owe interest even if I receive a refund?
Yes. Interest is calculated separately for each installment. Paying enough later does not necessarily eliminate interest for an earlier underpayment.
What is the underpayment interest rate?
The rate is 1% per month or fraction of a month. Any fraction of a month counts as a whole month.
How is the required annual payment generally calculated?
It is the smaller of 90% of the tax shown on your 2024 Connecticut return or 100% of the tax shown on your 2023 Connecticut return, if that 2023 return covered a 12-month period. Special rules apply to farmers, fishermen, and certain other filers.
Can uneven income reduce my interest?
Possibly. The annualized income installment method may reduce or eliminate one or more required installments when income varied during the year. Check Box A and complete Schedule A with the required supporting calculations.
Will I owe underpayment interest if my remaining tax is below $1,000?
No. First subtract Connecticut withholding and eligible PE Tax Credits from your total Connecticut income tax. If the result is less than $1,000, you are not subject to underpayment interest.