Connecticut Estimated Tax Payments (2026)

Do you have to pay estimated taxes in Connecticut?

Yes. If you're self-employed in Connecticut and expect to owe $1,000 or more in Connecticut income tax for 2026 after withholding, you must make quarterly estimated payments to Connecticut Department of Revenue Services. This is separate from your federal payments. Connecticut taxes income at graduated rates up to 6.99%.

When are Connecticut estimated taxes due in 2026?

Connecticut's 2026 quarterly payments are due April 15, June 15, September 15, and January 15, in four equal installments, on the same calendar as your federal payments.

• Q1, April 15, 2026

• Q2, June 15, 2026

• Q3, September 15, 2026

• Q4, January 15, 2027

How much should you set aside for Connecticut estimated taxes?

Plan to set aside 25% to 30% of your net self-employment profit to cover federal and Connecticut taxes combined, then confirm the exact amount with the calculator above. On $50,000 of net freelance profit, federal self-employment tax alone is about $7,065 (15.3% on 92.35% of your earnings). On top of that you'll owe federal income tax and Connecticut income tax at graduated rates up to 6.99%.

How do you avoid a Connecticut underpayment penalty?

To avoid a Connecticut underpayment penalty, pay the smaller of 90% of your 2026 Connecticut tax or 100% of your 2025 tax, in four on-time installments. Paying the full amount late doesn't help; each installment has to be on time. You can estimate a federal underpayment penalty here.

What deductions lower your Connecticut estimated taxes?

Because estimated taxes are based on your net profit, every business write-off you claim lowers what you owe each quarter. Common deductions for 1099 workers, reported on Schedule C, include the home-office deduction, car mileage, phone and internet, software, and supplies. You can also deduct half of your self-employment tax, and the federal Qualified Business Income (QBI) deduction can remove up to 20% of your qualified business income, which flows through to your Connecticut return in most states.

Keeper's 1099 tax calculator estimates your bill after deductions, and our write-off guides list the deductions for your line of work.

Note: Figures are current for the 2026 tax year and are for planning, not tax advice. Confirm the details with the Connecticut Department of Revenue Services before you file.

How to file quarterly taxes in Connecticut

Filing quarterly in Connecticut means two separate payments each period: one to the IRS for federal tax, and one to Connecticut Department of Revenue Services for your state taxes. Here’s how to do it.

1. Confirm you need to pay. You owe estimated payments when tax isn’t withheld from enough of your income — 1099 or freelance work, investment income, or other untaxed income. Federal and Connecticut run separate tests: the state generally requires estimated payments if you expect to owe $1,000 or more in Connecticut tax after withholding and credits, subject to its safe-harbor rules.
2. Calculate your federal estimate. Use the Form 1040-ES worksheet (or tax software). Estimate your full-year income, add your federal income tax and self-employment tax, subtract anything already withheld from a paycheck, and split the rest across the year. The estimate at the top of this page gives you a starting number.
3. Calculate your Connecticut estimate separately. Work out your Connecticut amount on its own using Form CT-1040ES. Don’t just send part of your federal payment to the state — the Connecticut calculation is separate, based on your Connecticut income tax, credits, and any Connecticut withholding.
4. Pay the IRS. Pay through IRS Direct Pay (or EFTPS) and choose the estimated tax / Form 1040-ES option. Select tax year 2026 and save the confirmation number. This money counts only toward your federal taxes.
5. Pay Connecticut separately. Make a second payment to myconneCT and select the Form CT-1040ES estimated payment for 2026. Save that confirmation too. This money counts only toward your Connecticut taxes.
6. Repeat on each deadline. For 2026, federal estimated payments are due April 15, 2026, June 15, 2026, September 15, 2026, and January 15, 2027. Connecticut uses those same four dates.

Steps reflect 2026 rules and are for planning, not tax advice.