Connecticut business tax extension
Connecticut doesn't take the federal extension on its own: extending Form CT-1120 takes Form CT-1120 EXT. The federal extension is Form 7004, due for calendar-year corporations and for partnerships and S corporations. In general, an extension gives you more time to file, not more time to pay.
Last updated · From Connecticut's own forms, instructions and laws, cited below
Does Connecticut accept the federal extension?
Connecticut requires its own request: file Form CT-1120 EXT, Application for Extension of Time to File Connecticut Corporation Business Tax Return. A federal extension alone does not extend the Connecticut return.
Connecticut's rules for each business return, as its own instructions and laws state them:
Corporations
- Return
- Form CT-1120, Corporation Business Tax Return (combined unitary groups file Form CT-1120CU)
- Due date
- The 15th day of the 5th month after the tax year ends (May 15 for a calendar year)
- Extension
- Connecticut requires its own request: file Form CT-1120 EXT, Application for Extension of Time to File Connecticut Corporation Business Tax Return. A federal extension alone does not extend the Connecticut return. File Form CT-1120 EXT electronically by the original due date and pay the tax shown. No reason is needed if federal Form 7004 was filed; without a federal extension the request needs reasonable cause. A June 30 year-end gets seven months.
- Extension length
- 6 months
- Extended due date
- The 15th day of the 11th month after the tax year ends (November 15 for a calendar year)
- Payment
- The tax is due by the original due date, even with an extension. To pay with the extension: Form CT-1120 EXT, paid electronically through myconneCT.
Partnerships and S corporations (Form CT-1065/CT-1120SI)
- Return
- Form CT-1065/CT-1120SI, Connecticut Composite Income Tax Return
- Due date
- The 15th day of the 3rd month after the tax year ends (March 15 for a calendar year)
- Extension
- Connecticut requires its own request: file Form CT-1065/CT-1120SI EXT, Application for Extension of Time to File Connecticut Composite Income Tax Return. A federal extension alone does not extend the Connecticut return. File the extension electronically by the original due date and pay the amount it shows. No reason is needed if federal Form 7004 was filed; otherwise the request needs reasonable cause.
- Extension length
- 6 months
- Extended due date
- The 15th day of the 9th month after the tax year ends (September 15 for a calendar year)
- Payment
- The tax is due by the original due date, even with an extension. To pay with the extension: Form CT-1065/CT-1120SI EXT, paid electronically.
Estates and trusts
- Return
- Form CT-1041, Connecticut Income Tax Return for Trusts and Estates
- Due date
- The 15th day of the 4th month after the tax year ends (April 15 for a calendar year)
- Extension
- Connecticut requires its own request: file Form CT-1041 EXT, Application for Extension of Time to File Connecticut Income Tax Return for Trusts and Estates. A federal extension alone does not extend the Connecticut return. File Form CT-1041 EXT by the original due date and pay the amount it shows. The extension is automatic on timely filing only if federal Form 7004 was filed; otherwise it needs reasonable cause. An IRS extension alone does not extend the Connecticut date.
- Extension length
- 5½ months
- Extended due date
- Five and a half months after the original due date (September 30 for a calendar year)
- Payment
- The tax is due by the original due date, even with an extension. To pay with the extension: Form CT-1041 EXT, through myconneCT or by mail.
When a due date in Connecticut falls on a weekend or legal holiday, it moves to the next business day. Connecticut's holidays can differ from the federal ones, so a rule not tied to a federal date is given without a computed date.
When is the federal business extension due?
Corporations, S corporations, partnerships, multi-member LLCs, estates and trusts extend their federal return with Form 7004, filed by the return's original due date. The extension is automatic: no reason is needed and the IRS doesn't approve it. We e-file it for a flat $9.95. These are the 2027 dates for calendar-year 2026 returns:
| Return | Who files | File the extension by | Extended to |
|---|---|---|---|
| Form 1065 Partnerships & multi-member LLCs, Form 7004 | 6 months | ||
| Form 1120-S S corporations (and LLCs taxed as S corps), Form 7004 | 6 months | ||
| Form 1120 C corporations (and LLCs taxed as C corps), Form 7004 | 6 months | ||
| Form 1041 Estates & trusts, Form 7004 | 5½ months | ||
| Form 990, 990-EZ, 990-PF Tax-exempt organizations & private foundations, Form 8868 | May 15, 2027 is a Saturday | 6 months |
Federal dates follow the IRS rule: a deadline on a weekend or legal holiday moves to the next business day. A fiscal-year business counts from its own year-end; see the fiscal-year deadline guide.
Tax-exempt organizations extend the 990 series with Form 8868, not Form 7004. Each return needs its own extension, so extending a business return does not extend its owners' personal returns.
Does an extension give more time to pay?
No. A federal extension moves the filing deadline only: tax owed is due by the original due date, and the IRS charges interest and the late-payment penalty on anything paid after it. Connecticut's instructions say the same for its returns: a Connecticut extension doesn't move the payment deadline. More in does an extension give you more time to pay?
Where are Connecticut's forms and instructions?
On the Connecticut Department of Revenue Services website, which has the current forms, instructions and online services. The rules on this page are summarized from the sources below. We e-file the federal extension; the Connecticut return and any Connecticut extension request go to the state.
Connecticut extension FAQ
Does Connecticut accept the federal business tax extension?
Connecticut requires its own request: file Form CT-1120 EXT, Application for Extension of Time to File Connecticut Corporation Business Tax Return. A federal extension alone does not extend the Connecticut return. The extension is 6 months. File Form CT-1120 EXT electronically by the original due date and pay the tax shown. No reason is needed if federal Form 7004 was filed; without a federal extension the request needs reasonable cause. A June 30 year-end gets seven months.
When is the Connecticut Form CT-1120 due?
The 15th day of the 5th month after the tax year ends (May 15 for a calendar year).
Does a Connecticut extension give more time to pay?
No. The tax is due by the original due date, even with an extension. To pay with the extension: Form CT-1120 EXT, paid electronically through myconneCT.
Does a Connecticut business still need a federal extension?
Yes, to get more time for its federal return: Form 7004, filed by April 15, 2027 for a calendar-year corporation or March 15, 2027 for a partnership or S corporation. Connecticut needs its own extension request as well.
Sources
- Connecticut State Department of Revenue Services, read
- Corporation Business Tax Information, read
- Form CT-1120 EXT, Application for Extension of Time to File Connecticut Corporation Business Tax Return, 2025 (Rev. 12/25), with instructions (PDF), read
- Form CT-1120, Connecticut Corporation Business Tax Return Instructions, 2025 (Rev. 12/25) (PDF), read
- Composite Income Tax Information, read
- Form CT-1065/CT-1120SI EXT, Application for Extension of Time to File Connecticut Composite Income Tax Return, 2025 (Rev. 12/25), with instructions (PDF), read
- Trust and Estates Tax Information, read
- Form CT-1041 EXT, Application for Extension of Time to File Connecticut Income Tax Return for Trusts and Estates, 2025 (Rev. 12/25), with instructions (PDF), read
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