The State of Connecticut requires that you apply for a business income tax extension, regardless of whether you owe additional state income taxes or expect a tax refund.

Most corporations may request a state tax extension by filing Form CT-1120 EXT (Application for Extension of Time to File Corporation Business Tax Return) with the Connecticut Department of Revenue Services.

If the form is completed accurately and on time, and any tax liability is paid by your original tax deadline, you will be granted an automatic six-month tax extension. If you were not granted a federal tax extension, you will need to provide a reason for requesting a state tax extension.

It’s important to note that filing a Connecticut business tax extension will not provide you with additional time to pay any tax balance due. The tax owed must still be paid by the original filing deadline (typically March 15) or interest and penalties will apply.

For additional information, please visit the State of Connecticut Department of Revenue Services website .

Request a business tax extension electronically:
Connecticut Department of Revenue Services Taxpayer Service Center (TSC-BUS)

Print and Mail:
Connecticut State Tax Extension Form CT-1120 EXT (C corporations)

Mail Form CT-1120 EXT with payment to:
Department of Revenue Services
State of Connecticut, P.O. Box 2974
Hartford, CT  06104-2974

Make check payable to: Commissioner of Revenue Services

Mail Form CT-1120 EXT without payment to:
Department of Revenue Services
State of Connecticut, P.O. Box 150406
Hartford, CT  06115-0406


Print and Mail:
Connecticut State Tax Extension Form CT-1065/CT-1120SI EXT (LLCs, Partnerships, and S corporations)

Mail Form CT-1065/CT-1120SI EXT with payment to:
Department of Revenue Services
State of Connecticut, P.O. Box 5019
Hartford, CT  06102-5019

Make check payable to: Commissioner of Revenue Services

Mail Form CT-1065/CT-1120SI EXT without payment to:
Department of Revenue Services
State of Connecticut, P.O. Box 2967
Hartford, CT  06104-2967