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Connecticut Business State Tax Extension I C Corporations Filing Guide

CT-1120EXT | Application for Extension of Time to File an Connecticut Income Tax Return for Corporation  ·  C Corporations  ·  Business Filing Guide

Overview

Connecticut C Corporations are subject to state corporate income tax 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 C Corporations return is April 15, 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 November 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 April 15, 2026 to avoid penalties and interest. Use the Connecticut | Online Tax Extension Payment to pay electronically. For mail-in payments, use CT-1120EXT | Application for Extension of Time to File an Connecticut Income Tax Return for Corporation and send to: Department of Revenue State of Connecticut P.O. Box 2934 Hartford, CT 06104-2934

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 April 15, 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 C Corporations return by November 15, 2026.

Final Thoughts

• Connecticut's business tax extension is straightforward once your federal extension is approved. Pay 100% of any tax due by April 15, 2026 and file your C Corporations return by November 15, 2026.
• Quick Reference Table
• State Abbreviation
• CT
• State Name
• Connecticut
• Business Entity Type
• C Corporations
• Extension Status
• Approved with Federal Extension
• Return Due Date
• April 15, 2026
• Extended Due Date
• November 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
• CT-1120EXT | Application for Extension of Time to File an Connecticut Income Tax Return for Corporation
• State Payment Agency
• Connecticut | Department of Revenue Services
• Mailing Address with Payment
• Department of Revenue State of Connecticut P.O. Box 2934 Hartford, CT 06104-2934
• 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 November 15, 2026

Quick Reference Table

State Abbreviation	CT
State Name	Connecticut
Business Entity Type	C Corporations
Extension Status	Approved with Federal Extension
Return Due Date	April 15, 2026
Extended Due Date	November 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	CT-1120EXT | Application for Extension of Time to File an Connecticut Income Tax Return for Corporation
State Payment Agency	Connecticut | Department of Revenue Services
Mailing Address with Payment	Department of Revenue State of Connecticut P.O. Box 2934 Hartford, CT 06104-2934
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.