Introduction
Searching for "1040-CT"? You almost certainly mean Form CT-1040, the Connecticut Resident Income Tax Return. This guide covers the Connecticut individual income-tax filing and payment dates that fall in 2027.
The timing trips people up. A return filed in 2027 reports tax year 2026. Estimated payments made in April, June and September 2027 apply to tax year 2027. January 2027's payment still belongs to 2026.
Below you'll find the deadline calendar, extension rules, estimated payments, penalties, and a filing checklist. A full 2027 calendar from the Connecticut Department of Revenue Services (DRS) may not be posted yet, so the dates below follow its standing rules. Confirm them with DRS before you pay.
Key Takeaways
- CT-1040 is Connecticut's resident return, separate from federal Form 1040, sales-tax returns and business forms.
- The 2026 return is due April 15, 2027, based on current DRS rules.
- A six-month filing extension does not extend the payment deadline.
- Check every date with DRS for holiday shifts, law changes and disaster relief.
- Keep confirmations, payment records and a copy of what you filed.
Who Needs to File Form CT-1040?
CT-1040 is for Connecticut residents. Nonresidents and part-year residents file CT-1040NR/PY instead. Your residency facts decide which form applies.
Residency categories
- Full-year resident: Connecticut domicile all year, or a Connecticut permanent abode all year plus more than 183 Connecticut days.
- Part-year resident: you moved your permanent legal residence into or out of Connecticut during the year.
- Nonresident: neither of the above, but you may still owe tax on Connecticut-source income.
One exception: a Connecticut domiciliary with no Connecticut permanent abode all year, an outside permanent abode all year, and no more than 30 Connecticut days can be treated as a nonresident.
Filing triggers
These gross income thresholds are the 2025 amounts from DRS. Confirm the figures in the current-year instructions for your filing year. Your gross income must exceed:
| Filing status | Gross income exceeds |
|---|---|
| Married filing separately | $12,000 |
| Single | $15,000 |
| Head of household | $19,000 |
| Married filing jointly / qualifying surviving spouse | $24,000 |
Gross income counts income from inside and outside Connecticut. You may also need to file if:
- Connecticut tax was withheld
- You made estimated or extension payments
- You owe federal alternative minimum tax
- You claim the Connecticut earned income tax credit
When your situation gets more complex
CT-1040 is an individual return. It doesn't cover every business deadline. Some situations need extra schedules or a professional's review:
- Self-employment income: you may need estimated payments on Form CT-1040ES.
- Income taxed by another state: claim a credit on CT-1040 Schedule 2.
- Part-year or nonresident income: Schedule CT-SI allocates Connecticut-source items.
- Pass-through income: Schedule CT K-1 modifications flow into your individual return.
Important Connecticut Tax Deadlines for 2027
Each date below is labeled by tax year. January 2027 comes from the published 2026 CT-1040ES. The rest are derived from standing DRS rules, including its policy of moving weekend and legal-holiday deadlines to the next business day.
| 2027 date | What's due | Tax year |
|---|---|---|
| Friday, January 15, 2027 | Fourth estimated installment | 2026 |
| Thursday, April 15, 2027 | Return, balance payment, and CT-1040 EXT if needed | 2026 |
| Thursday, April 15, 2027 | First estimated installment | 2027 |
| Tuesday, June 15, 2027 | Second estimated installment | 2027 |
| Wednesday, September 15, 2027 | Third estimated installment | 2027 |
| Friday, October 15, 2027 | Return under a valid six-month extension | 2026 |
| Tuesday, January 18, 2028 | Fourth estimated installment | 2027 |
Why the last date moves
January 15, 2028 is a Saturday, and January 17 is the Martin Luther King Jr. holiday. That pushes the final 2027 installment to Tuesday, January 18, 2028.
April 15, 2027 is not shifted by Emancipation Day (April 16) or Patriots' Day. Connecticut doesn't list Patriots' Day among its statutory holidays.
Where to check for changes
Look at the DRS individual income-tax and estimated-tax pages for last-minute changes, special postponements and disaster relief. Past relief, such as DRS notice TSSB 2024-6.1 for weather-affected taxpayers, was handled case by case. It says nothing about 2027.
Connecticut Estimated Tax Payments, Extensions, and Late Filing
Who needs to make estimated payments
Estimates are for people whose withholding doesn't cover their tax: the self-employed, independent contractors, investors and others with untaxed income. The CT-1040ES instructions set the test:
- Expected unpaid Connecticut tax of $1,000 or more, and
- Withholding and credits below the required annual payment.
The safe harbor is the lesser of 90% of current-year tax or 100% of prior-year tax, when the prior-year return covered a full 12 months. Uneven income? Form CT-2210 annualization can reduce required installments. Using it for one installment means using it for all.
Underpayment interest runs 1% per month or fraction, calculated for each installment separately.
The 2027 payment schedule
- January 15, 2027: installment four for 2026
- April 15, 2027: installment one for 2027
- June 15, 2027: installment two for 2027
- September 15, 2027: installment three for 2027
- January 18, 2028: installment four for 2027
Pay through myconneCT by ACH debit (no fee) or card (convenience fee). You can also mail a coupon and check.
How to request an extension
- Estimate your 2026 tax and compare it with what you've already paid.
- File CT-1040 EXT by April 15, 2027 if you expect to owe more.
- Pay your estimated balance with the request.
- File the completed return by October 15, 2027.
The CT-1040 EXT form supports a six-month extension, and a federal Form 4868 backs the request. A federal extension is recognized automatically only when you expect no additional Connecticut tax. Otherwise, file CT-1040 EXT.
Filing time is not paying time
A filing extension doesn't move the payment date. To avoid the late-payment penalty, pay at least 90% of the tax by April 15 and the rest with the return. Interest still runs on any balance.
Can't pay in full? File anyway. Filing on time avoids extra penalties, and DRS offers help:
- CT-1127 hardship extension, filed by the original deadline, may grant up to six months. Interest still applies.
- Payment plan: available when filings are current, liabilities are $50,000 or less, and terms run 12 months or less.
What happens if you miss a deadline
Under Connecticut's income-tax statute, late payment draws a 10% penalty on unpaid tax plus 1% interest per month or fraction from the original due date.
- With no tax due, DRS may still impose a $50 late-filing penalty.
- If DRS prepares your return, the penalty is the greater of 10% of the balance or $50.
- Amending? Use CT-1040X. Refund claims generally expire three years after the original due date. Federal changes must be reported within 90 days of final determination.
How to Prepare and File Your Connecticut Return
Your document checklist
- Completed federal return
- W-2s and 1099s
- Connecticut withholding totals
- Estimated-payment confirmations
- Last year's Connecticut return
- Residency details, including days spent in Connecticut
- Records behind any credits or deductions
Filing and paying
You can file and pay through several channels:
- myconneCT: DRS's online system, with an immediate confirmation page and printable receipt
- Modernized e-File: Through a preparer or commercial software
- Approved free-filing vendors: Linked by DRS for qualifying taxpayers
- Paper returns: Accepted by mail
Don't mail a second copy of an e-filed return. If you're mailing a payment for one, include CT-1040V.
Refund status is tracked separately in "Where's my Refund?", which asks for your SSN, tax year and exact whole-dollar refund amount. Keep the confirmation receipt, and retain the return, worksheets and supporting records for the limitations period (usually three years from the later of the due date or filing date).
Income tax versus sales tax
CT-1040 is an individual income-tax return. Sales and use tax runs on a separate track: its own DRS registration, Form OS-114, and a monthly, quarterly or annual frequency. Those returns are generally due the last day of the month after the filing period.
Getting help
VJM Global's CPAs and chartered accountants support US taxpayers and businesses with bookkeeping, tax compliance and return preparation. That includes organizing records, tracking filing dates and reviewing Connecticut compliance needs. The work is done remotely, with no Connecticut office.
Frequently Asked Questions
What is the deadline for taxes in CT?
For tax year 2026, the Connecticut individual return is due April 15, 2027. DRS moves weekend and holiday deadlines to the next business day. Confirm the date with DRS before filing.
What are the monthly sales tax due dates in Connecticut?
Sales-tax deadlines are separate from CT-1040. Your assigned filing frequency decides the date, and returns are generally due the last day of the month following the period. Check the DRS 2027 schedule.
What is Form CT-1040?
It's Connecticut's resident individual income-tax return. It differs from federal Form 1040 and from CT-1040NR/PY, which covers nonresidents and part-year residents.
When are Connecticut estimated tax payments due in 2027?
January 15 (2026 tax year), then April 15, June 15 and September 15 (2027 tax year). The final 2027 installment falls on January 18, 2028.
Does Connecticut give an extension to file Form CT-1040?
Yes. File CT-1040 EXT by April 15, 2027 for six months, until October 15, 2027. A federal extension is recognized automatically only if you expect no added Connecticut tax. Verify with DRS.
Do I still need to pay Connecticut tax by the original deadline if I file an extension?
Yes. The extension covers filing, not payment. Pay at least 90% by April 15 to avoid the late-payment penalty. Interest still applies to any unpaid balance.
