Connecticut Estimated Tax Payments: 2026 Due Dates, Who Pays and How

2026 estimated tax due dates

For calendar-year taxpayers, Connecticut and the IRS use the same four dates for the 2026 tax year. Each payment covers income you earned in the months before it.

The next one coming up is January 15, 2027. If a due date lands on a weekend or legal holiday, the payment is on time if it's made the next business day. Connecticut treats a mailed payment as on time if the postmark is on or before the due date.

For a full list of 2026 and 2027 dates, including W-2, 1099 and business return deadlines, see our Connecticut and federal tax deadline calendar.

Who has to make estimated payments

Estimated payments are how you pay tax on income that doesn't have tax withheld. That usually means:

• Freelancers, gig workers and independent contractors paid on a 1099
• Sole proprietors and single-member LLC owners
• Partners and S-Corp owners whose share of profit isn't covered by withholding
• People with sizable rental income, interest, dividends or capital gains

Connecticut's test. You must make Connecticut estimated payments if your Connecticut income tax, after withholding and any pass-through entity tax credit, will be $1,000 or more, and your withholding (plus that credit) will be less than your "required annual payment" (explained below).

The IRS test. It works the same way at the federal level: you generally need to pay estimated tax if you expect to owe at least $1,000 for 2026 after subtracting withholding and refundable credits, and your withholding won't cover the safe-harbor amount.

Connecticut has no local city or town income tax, so you only deal with these two: the IRS and the Connecticut Department of Revenue Services (DRS).

How much to pay

Both Connecticut and the IRS want each payment to be about 25% of your "required annual payment." That required amount is the smaller of two numbers, often called the safe harbors:

The "last year" option is popular because the number is already known: it's on your 2025 return. If your income jumps in 2026, paying based on last year's tax can keep you clear of underpayment charges, but you'll still owe the difference when you file in April. If your income drops, paying 90% of this year's lower tax may let you pay less now.

Uneven income? If most of your income comes late in the year, you don't have to pretend it came in evenly. Connecticut's annualized income installment method (Worksheet CT-1040 AES) and the federal version (Form 2210, Schedule AI) let you match payments to when you actually earned the money.

Have a W-2 job too? Instead of quarterly payments, you can have more tax withheld from your paycheck: Form CT-W4 for Connecticut and Form W-4 for federal. For federal purposes, withholding is generally treated as paid evenly through the year, so extra withholding late in the year can help cover an earlier short quarter. Our Connecticut paycheck calculator shows what comes out of each check now.

How to pay Connecticut and the IRS

Connecticut

• myconneCT (portal.ct.gov/DRS-myconneCT): pay from a bank account online and get an immediate confirmation.
• Credit or debit card: accepted, but the card processor charges a convenience fee.
• By mail: use the 2026 Form CT-1040ES coupon with a check. The coupons are year-specific, so don't reuse an old one.

IRS

• IRS Direct Pay or your IRS Online Account: free bank-account payments; choose "Estimated tax" and tax year 2026.
• EFTPS: free, but you have to enroll first, so set it up before the due date.
• Card, or check with a Form 1040-ES voucher: also accepted. Card payments carry a processing fee.

Save every confirmation number. When your return is prepared, the total of your four payments goes on both returns, and mismatches are one of the most common reasons for refund delays.

If you miss or short a payment

Connecticut charges interest of 1% per month (or part of a month) on each underpaid installment, figured separately for each quarter, until it's paid or until the April due date of the return. That means paying more in January won't fully erase interest on a short April payment. You figure it on Form CT-2210. The IRS charges an underpayment penalty that works like interest, figured on Form 2210.

If you've fallen behind, the usual fix is simple: make a catch-up payment as soon as you can. The charge stops growing on the amount you pay.

Simple ways to stay on track

• Put the four dates on your calendar now, with a reminder a week ahead.
• Move a share of every payment you receive into a separate account for taxes so the money is there on the due date.
• Re-check your numbers mid-year. If business is much better or worse than last year, adjust the June and September payments.
• Pay online. You get proof of payment right away and nothing gets lost in the mail.
• New to self-employment? Start with our guide to 1099 taxes in Connecticut, which explains self-employment tax and what to set aside.