Connecticut C Corporation Tax Deadlines 2026

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

The Connecticut C Corporation tax return is due May 15, 2026 for the 2026 tax year. An extension is available until Nov 15, 2026.

Does Connecticut require C Corporation estimated tax payments?

Yes, Connecticut requires estimated tax payments for C Corporation entities. The quarterly due dates are: Apr 15, 2026, Jun 15, 2026, Sep 15, 2026, Dec 15, 2026. Penalties may apply if you underpay or miss a deadline.

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

C Corporation entities in Connecticut file using Form Form CT-1120. 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 C Corporation tax return?

Yes. Connecticut allows an extension for C Corporation returns until Nov 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 May 15, 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 C Corporation taxes?

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