Connecticut Personal Tax ExtensionForm CT-1040 EXT

Connecticut Personal Income Tax Extension – Tied to Your Federal Extension

The Connecticut Department of Revenue Services (DRS) aligns directly with the federal extension system. Taxpayers who receive a federal extension by filing IRS Form 4868 are automatically granted a six-month extension to file their Connecticut personal income tax return – pushing the deadline from April 15, 2026, to October 15, 2026. No separate Connecticut form is required to obtain the extension. However, interest begins accruing on any unpaid Connecticut tax from April 15 onward.

How the Federal Connection Works

Connecticut does not require a separate state extension application. Your IRS Form 4868 – or any other valid federal extension – automatically extends your Connecticut filing deadline by six months. There is no Connecticut approval process to follow. Keep a copy of your federal extension confirmation when you eventually file your return.

Using Form CT-1040 EXT

Form CT-1040 EXT (Application for Extension of Time to File Connecticut Income Tax Return for Individuals) is used when mailing a payment with your extension. It ensures your payment is credited to the correct account. If you are paying electronically or owe no balance, you do not need to file Form CT-1040 EXT.

Late Filing and Payment Penalties

Failing to file by October 15 results in a penalty of the greater of $50 or 10% of unpaid tax. A separate 10% late payment penalty applies to any balance not paid by April 15. However, if an extension is in place and at least 90% of tax owed is paid by April 15, the failure-to-pay penalty is waived on any remaining balance paid by October 15. Interest on unpaid amounts runs from the original due date. Filing on time and paying what you owe by April 15 eliminates all penalties and stops interest from accumulating.

Best Practices

• ✓File IRS Form 4868 by April 15 – Connecticut’s extension depends on it.
• ✓Pay your full Connecticut balance by April 15, 2026, to stop interest from running.
• ✓Use portal.ct.gov/DRS-myconneCT or portal.ct.gov/DRS-myconneCT for ACH payments – no login required at portal.ct.gov/DRS-myconneCT.
• ✓Submit Form CT-1040 EXT only if mailing a payment – not required for the extension itself.
• ✓File your completed Connecticut return by October 15, 2026.

Connecticut’s extension is straightforward once you have a federal extension in hand – no separate state paperwork required. The key is addressing your payment obligation by April 15, since interest accrues from that date regardless of extension status. Use Connecticut’s online portals for fast, confirmed payments and avoid the cost of carrying a balance into the fall.

Quick Reference Table

Mailing Address with Payment