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Connecticut Business State Tax Extension I LLCs / Partnerships

Form CT-1065/CT-1120SI EXT | Application for Extension of Time to File Connecticut Pass-Through Entity Tax Return  ·  LLCs / Partnerships  ·  Business Filing Guide

Overview

Connecticut LLCs and partnerships are subject to state tax filing requirements, administered by the Connecticut | Department of Revenue Services. Connecticut grants an automatic extension tied to an approved IRS extension, making the process simple for businesses that have already filed IRS Form 7004.

Original Filing Deadline

• The original due date for the Connecticut LLCs / Partnerships return is March 16, 2026. File or remit full payment by this date to remain in good standing.
• Extension Period & Extended Deadline
• Connecticut automatically grants an extension to file, provided you have obtained an approved federal extension from the IRS by filing IRS Form 7004. With a valid IRS extension, the Connecticut extended deadline becomes September 15, 2026. No separate state extension form is required—the federal extension serves as your Connecticut extension.

Payment Is Still Due by Original Deadline

The extension applies to filing only—it is not an extension to pay taxes owed. Any outstanding tax liability must be paid by the original due date of March 16, 2026 to avoid penalties and interest. Use the Connecticut | Online Tax Extension Payment to pay electronically. For mail-in payments, use Form CT-1065/CT-1120SI EXT | Application for Extension of Time to File Connecticut Pass-Through Entity Tax Return and send to: N/A

Late Filing and Payment Penalties

• Failure to File: $50 penalty, or 10% of the tax due, whichever is greater.
• Failure to Pay: $50 penalty, or 10% of the tax due, whichever is greater.

Best Practices

• Estimate and pay your Connecticut business tax by March 16, 2026 to avoid interest and penalties.
• File IRS Form 7004 with the IRS to secure your federal extension, which Connecticut automatically honors.
• Use the state online payment portal for fast, convenient electronic payment.
• Set a reminder to file your completed Connecticut LLCs / Partnerships return by September 15, 2026.

Final Thoughts

• Connecticut's business tax extension is straightforward once your federal extension is approved. Pay 100% of any tax due by March 16, 2026 and file your LLCs / Partnerships return by September 15, 2026.
• Quick Reference Table
• State Abbreviation
• CT
• State Name
• Connecticut
• Business Entity Type
• LLCs / Partnerships
• Extension Status
• Approved with Federal Extension
• Return Due Date
• March 16, 2026
• Extended Due Date
• September 15, 2026
• Other Information
• Connecticut grants your business an automatic 6-month extension provided you have obtained an approved IRS extension. The extension is NOT an extension to pay any taxes you may have due. Tax payments are due by the original return due date.
• Online Payment
• Connecticut | Online Tax Extension Payment
• Payment Voucher Form
• Form CT-1065/CT-1120SI EXT | Application for Extension of Time to File Connecticut Pass-Through Entity Tax Return
• State Payment Agency
• Connecticut | Department of Revenue Services
• Mailing Address with Payment
• N/A
• Failure to File Penalties
• $50 penalty, or 10% of the tax due, whichever is greater.
• Failure to Pay Penalties
• $50 penalty, or 10% of the tax due, whichever is greater.

Working with a Tax Professional

Business tax returns are complex—a licensed CPA or Enrolled Agent can maximize deductions, ensure accurate calculations, and handle filing on your behalf. Here's how working with a TaxPro typically goes:

1. 1Get matched with a verified U.S.-based CPA or Enrolled Agent
2. 2Upload your business documents via secure drag-and-drop
3. 3Review and approve your return with upfront, transparent fees
4. 4Your TaxPro files your Connecticut return by September 15, 2026

Quick Reference Table

State Abbreviation	CT
State Name	Connecticut
Business Entity Type	LLCs / Partnerships
Extension Status	Approved with Federal Extension
Return Due Date	March 16, 2026
Extended Due Date	September 15, 2026
Other Information	Connecticut grants your business an automatic 6-month extension provided you have obtained an approved IRS extension. The extension is NOT an extension to pay any taxes you may have due. Tax payments are due by the original return due date.
Online Payment	Connecticut | Online Tax Extension Payment
Payment Voucher Form	Form CT-1065/CT-1120SI EXT | Application for Extension of Time to File Connecticut Pass-Through Entity Tax Return
State Payment Agency	Connecticut | Department of Revenue Services
Mailing Address with Payment	N/A
Failure to File Penalties	$50 penalty, or 10% of the tax due, whichever is greater.
Failure to Pay Penalties	$50 penalty, or 10% of the tax due, whichever is greater.