2025 Connecticut Quarterly Estimated Tax Payments

The CT Department of Revenue Services (DRS) requires you to make quarterly estimated tax payments for calendar year 2025 if both of the following apply:

• you expect to owe at least $1,000 in State of CT income tax for 2025, after subtracting CT tax withholding and credits, and
• you expect CT withholding and credits to be less than the smaller of:
  • 90% of the income tax to be shown on your 2025 CT tax return, or
  • 100% of the income tax shown on your 2024 CT tax return (only applies if your 2024 tax return covered 12 months’ otherwise; utilize the 90% test above only). Note:  If you were a nonresident or part-year resident of Connecticut in 2024 and you did not have Connecticut-sourced income during 2024, you must use the 90% test above only.

You are not required to make CT estimated tax payments if:

• You were a CT resident during the 2024 taxable year and you did not file a 2024 CT income tax return because you had no CT income tax liability, or
• You were a nonresident or part-year resident with CT source income during the 2024 taxable year and you did not file a 2024 income tax return because you had no CT income tax liability.

To calculate your State of CT quarterly estimated tax payments, you must estimate your adjusted gross income, deductions, and credits for the calendar year 2025. Form CT 1040-ES includes an Estimated Connecticut Income Tax Worksheet to help you calculate your CT estimated tax payments.

Frequently Asked Questions

1. What are the filing dates for CT quarterly estimated tax payments?

2. How do I make CT quarterly estimated tax payments?

The CT DRS provides methods to pay quarterly estimated taxes:

• You may pay by check and mail your payment with a payment voucher form, Form CT-1040ES;
• You may file and pay via the DRS website. You may also make your payments by credit card.

3. What if I do not pay enough CT income tax in a timely manner for the calendar year?

Generally, if you do not pay enough tax either through withholding or making estimated tax payments, you may be charged interest. Interest is calculated at a rate of 1% per month on the underpayment of tax.

4. How do I obtain additional information regarding CT quarterly estimated tax payments?

For additional information regarding CT quarterly estimated tax payments, please refer to the Form CT-1040ES instructions and also CT IP 2018(16) or consult your personal tax advisor.