The CT Department of Revenue Services (DRS) requires you to make quarterly estimated tax payments for calendar year 2026 if both of the following apply:
- you expect to owe at least $1,000 in State of CT income tax for 2026, 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 2026 CT tax return, or
- 100% of the income tax shown on your 2025 CT tax return (only applies if your 2025 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 2025 and you did not have Connecticut-sourced income during 2025, 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 2025 taxable year and you did not file a 2025 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 2025 taxable year and you did not file a 2025 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 2026. Form CT 1040-ES includes an Estimated Connecticut Income Tax Worksheet to help you calculate your CT estimated tax payments.