Connecticut S Corporation Tax Deadlines 2026

When is the S Corporation tax filing deadline in Connecticut for 2026?

The Connecticut S Corporation tax return is due Mar 16, 2026 for the 2026 tax year. An extension is available until Sep 15, 2026.

Does Connecticut require S Corporation estimated tax payments?

Estimated payments are not typically required at the entity level for S Corporation in Connecticut, but confirm with Connecticut Department of Revenue Services.

What form do I file for a S Corporation in Connecticut?

S Corporation entities in Connecticut file using Form Form CT-1120SI. You can download the form from Connecticut Department of Revenue Services at https://portal.ct.gov/DRS.

Can I get an extension for my Connecticut S Corporation tax return?

Yes. Connecticut allows an extension for S Corporation returns until Sep 15, 2026. Note that an extension gives you more time to file, not more time to pay — any tax owed is still due by the original deadline of Mar 16, 2026.

What are the penalties for filing late in Connecticut?

Connecticut typically charges a failure-to-file penalty (usually 5% of unpaid tax per month, up to 25%) and a failure-to-pay penalty (usually 0.5-1% per month). Interest also accrues on unpaid balances. Filing for an extension by the original deadline avoids the failure-to-file penalty but not the failure-to-pay penalty.

Where can I file Connecticut S Corporation taxes?

File through Connecticut Department of Revenue Services. Visit https://portal.ct.gov/DRS for e-filing options, downloadable forms, and payment portals.