Introduction
Connecticut income tax is pay-as-you-go. Employers withhold from wages, but freelance fees, rent, dividends and capital gains arrive with nothing taken out. If that untaxed income is large enough, the state expects you to pay during the year, not all at once in April.
This guide helps you work out whether you must pay, how much to send, and when. It also covers how to pay and how to avoid mixing up federal and state forms or addresses.
Thresholds, dates and addresses below reflect the 2026 tax year. Confirm every figure against the latest Connecticut Department of Revenue Services (DRS) materials before you pay.
Key Takeaways
- Form CT-1040ES is Connecticut's estimated-payment coupon, separate from federal Form 1040-ES.
- Self-employment, rental, investment and capital-gain income without withholding often trigger payments.
- Your amount and due dates depend on tax year, withholding, credits, residency and expected income.
- Pay DRS, never the IRS, and keep a confirmation or mailing record for every installment.
What Is Form CT-1040ES and Who Must Pay?
What CT-1040ES is used for
CT-1040ES is the 2026 Estimated Connecticut Income Tax Payment Coupon for Individuals. The PDF also includes the instructions, worksheets and tax tables. Federal Form 1040-ES covers only your IRS estimates, and the two are paid to different agencies.
Who may need to make payments
Estimated payments are common for:
- Sole proprietors, freelancers and independent contractors
- Partners and owners of pass-through businesses
- Investors and landlords
- Retirees whose withholding falls short
- Anyone with a large one-time gain, prize or other untaxed income
DRS lists self-employment, rent, capital gains, interest, dividends, unemployment compensation, gambling winnings, alimony and federally taxable Social Security as income that may arrive without Connecticut withholding.
Residency also shapes what you report. Residents report income from everywhere. Nonresidents report Connecticut-source income only.
Part-year residents report all income earned while resident and Connecticut-source income while nonresident. Special accrual rules can apply when residency changes.
The two-part test
According to DRS resident guidance, you must make estimated payments when both of these are true:
- Your Connecticut tax, after Connecticut withholding and the allowable Pass-Through Entity (PE) Tax Credit, is $1,000 or more.
- Your expected withholding, including that credit, is less than your required annual payment.
Use Connecticut's test, not federal thresholds.
Who may not need to pay
You are generally exempt if you were a Connecticut resident in 2025 and filed no 2025 return because you owed no Connecticut tax. The same applies to a 2025 nonresident or part-year resident with Connecticut-source income who owed nothing.
Having no Connecticut-source income at all in 2025 is different: you must use 90% of your 2026 tax. Check the current-year instructions to confirm your case.
How to Estimate Your Connecticut Income Tax Payments
Gather projected income and existing payments
List your expected Connecticut-taxable income:
- Wages and self-employment profit
- Interest, dividends and rent
- Capital gains and retirement distributions
Then note expected Connecticut withholding, the PE Tax Credit and other credits. Residents include worldwide income. Nonresidents include only Connecticut-source income.
Use the CT-1040ES worksheet
The 2026 worksheet moves in stages:
- Lines 1-3: federal AGI, Connecticut modifications, Connecticut AGI
- Tax Calculation Schedule: subtract the personal exemption, then apply initial tax, phase-out add-back, recapture and personal tax credit
- Lines 4-12: apportionment, qualifying-jurisdiction credits, Connecticut alternative minimum tax and Schedule CT-IT credits
- Lines 13-15: your required annual payment
- Lines 16 and 16a: subtract withholding and the estimated PE Tax Credit
The 2026 marginal rates apply to Connecticut taxable income, not gross receipts:
| Rate | Single / MFS | MFJ / surviving spouse | Head of household |
|---|---|---|---|
| 2% | Up to $10,000 | Up to $20,000 | Up to $16,000 |
| 4.5% | To $50,000 | To $100,000 | To $80,000 |
| 5.5% | To $100,000 | To $200,000 | To $160,000 |
| 6% | To $200,000 | To $400,000 | To $320,000 |
| 6.5% | To $250,000 | To $500,000 | To $400,000 |
| 6.9% | To $500,000 | To $1,000,000 | To $800,000 |
| 6.99% | Over $500,000 | Over $1,000,000 | Over $800,000 |
Table B is not the whole calculation. Maximum personal exemptions are $15,000 (single), $24,000 (MFJ), $12,000 (MFS) and $19,000 (head of household), and they phase out as Connecticut AGI rises.
The form's Tables A, C, D and E handle those phase-outs, add-back, recapture and credit.
Determine the required annual payment
Your required annual payment is the lesser of 90% of your 2026 Connecticut tax or 100% of your 2025 Connecticut tax, as long as the prior return covered 12 months. The form states no higher multiplier for high earners. Subtract withholding and the PE Tax Credit to see what must go in through installments.
Convert the annual estimate into installments
Installments are normally 25% each. Suppose your required annual payment after withholding is $8,000. Each of the four installments would be $2,000.
Equal payments don't suit everyone. If income arrives late in the year, annualization lets you pay less early and more later.
The current form points to DRS guide IP 2018(11), which uses cumulative calculations at periods ending March 31, May 31, August 31 and December 31. Keep Worksheet CT-1040 AES for your records.
Recalculate when circumstances change
Revisit your estimate after:
- A new contract or job change
- An investment sale or large distribution
- A business loss
- A withholding adjustment
- A move into or out of Connecticut
Apply the new figure to the remaining installments and save the updated worksheet. The 2026 coupon instructions give no separate amended-estimate filing procedure, so ask DRS if you need one.
When Are CT Estimated Tax Payments Due?
Calendar-year deadlines
| Installment | Due date | Cumulative share |
|---|---|---|
| First | April 15, 2026 | 25% |
| Second | June 15, 2026 | 50% |
| Third | September 15, 2026 | 75% |
| Fourth | January 15, 2027 | 100% |
A date landing on a weekend or legal holiday moves to the next business day. The January 2027 payment is the fourth for 2026 tax, not the first for 2027. Look for the 2027 form separately.
Fiscal-year and midyear situations
Fiscal-year taxpayers use their federal estimated-tax installment dates. State law sets the same four-installment pattern, with corresponding months for a fiscal year. The form publishes no separate calendar for income that starts midyear. Annualization may reduce or eliminate earlier installments, and DRS can confirm your timing.
Why timely payment matters
Connecticut measures each installment on its own. Paying everything with your return doesn't erase underpayment interest on earlier missed installments. An estimate is timely if DRS receives it by the due date or the USPS cancellation mark is dated on or before it. Schedule electronic payments early and save the confirmation.
How to Make a CT-1040ES Payment
Pay online through myconneCT
You don't need a login to pay as an individual. The steps:
- Open the DRS myconneCT site and choose "Make a Bill Payment, Estimated Payment or Return payment." Logged-in users choose "Make an Estimated Payment."
- Select the Individual Income Tax account and the correct tax year.
- Enter your taxpayer identification details.
- Enter your bank account (ACH debit) or card details.
- Pick the payment date and submit.
- Save or print the confirmation number.
ACH debit from a checking or savings account carries no ACH fee. Cards (American Express, Discover, MasterCard, Visa) carry a convenience fee disclosed before you accept, and you can cancel at that point.
ACH credit isn't available for individual income tax. Most ACH debit payments can be scheduled up to 45 days ahead, but card payments can't be future-dated.
Select the correct payment type
Choose the estimated payment option, not these look-alikes:
- "File an Extension"
- "Account Bill Payment"
- "Return/Period Payment"
- Withholding or Pass Through Entity accounts, which are separate tax types
A misapplied payment can leave your installment looking unpaid.
Mail a payment with the CT-1040ES voucher
Complete the coupon in blue or black ink. Make a signed check payable to Commissioner of Revenue Services and write "2026 Form CT-1040ES" on it. Adding your SSN is optional.
Paper clip the check to the coupon, and never send cash. Don't enclose the worksheet, and don't mail the coupon if you paid by card.
Mail to: Department of Revenue Services, PO Box 2932, Hartford CT 06104-2932. Never use an IRS address, and recheck the address printed on the current voucher.
Electronic versus mailed payments
| Factor | Online | Check by mail |
|---|---|---|
| Speed | Immediate or scheduled | Depends on mail |
| Proof | Confirmation number | USPS cancellation mark, tracking |
| Cost | No ACH fee; card fee applies | Postage |
| Risk | Wrong payment type | Delay, lost mail |
Confirm and document the payment
Keep a file for each installment:
- Confirmation page and email
- Bank or card record
- Copy of the voucher and check
- Date mailed and tracking details
- The tax year and installment it covers
How to Avoid Underpayment Penalties and Common Mistakes
Understand how underpayment is charged
Connecticut charges 1% per month or fraction of a month on each installment's shortfall, under Chapter 229. The shortfall is the required installment minus what you paid on time.
The 2026 form sets the cutoff at April 15, 2027. Later payments apply to the earliest unpaid installments first, and a refund at filing doesn't cancel earlier interest.
Other points to know:
- DRS says interest cannot be waived. Civil-penalty waivers are separate.
- A fourth-installment exception applies if you file and pay in full by January 31 of the following year (weekends and holidays can shift the due date).
- Qualifying farmers and fishermen have one installment and avoid interest by filing and paying fully by March 1, 2027.
- DRS still lists 2025 Form CT-2210 as the current underpayment form; use that version and its instructions until a 2026 form is published.
Address uneven income and special situations
Schedule A of CT-2210 handles annualization when income arrives unevenly. Common triggers include:
- Late-year lottery wins, investment gains or new self-employment income
- A mid-year move into Connecticut
If you annualize one installment, you must annualize all of them.
Get a professional review if you have:
- Large one-time gains
- Part-year residency
- Nonresident Connecticut-source income
- Changing withholding
Get help when the calculation is complex
VJM Global's tax compliance and advisory professionals support U.S.-based taxpayers and businesses with Connecticut estimated-tax work. They can organize income data, review installment calculations and maintain clear payment and filing records.
Frequently Asked Questions
How do I make a CT 1040 ES payment?
Pay online through DRS myconneCT using the estimated payment option, or mail the CT-1040ES coupon with a check. Select the correct tax year and the Individual Income Tax account either way.
When are Connecticut estimated tax payments due?
For 2026 tax: April 15, June 15 and September 15, 2026, and January 15, 2027. Weekend or holiday dates move to the next business day. Fiscal-year filers use their federal installment dates.
What payment type should I select?
Choose the individual estimated payment option. It differs from an extension, an account bill payment, a return payment, or withholding and Pass Through Entity payments. Never pay federal estimates through DRS.
Where do I mail Connecticut estimated tax payments?
Use the address on your current coupon. For 2026 it is Department of Revenue Services, PO Box 2932, Hartford CT 06104-2932. Never use an IRS address.
Does Connecticut require estimated tax payments?
Yes, if your Connecticut tax after withholding and PE Tax Credit is $1,000 or more and expected withholding falls short of your required annual payment. Exceptions apply, so check the current instructions.
How can I estimate my Connecticut state income taxes?
Use the CT-1040ES worksheet. Project your Connecticut-taxable income, apply the tax tables, subtract withholding and credits, and revise the estimate whenever your income changes.
