C Corporation Tax Deadlines in Connecticut
Federal and state filing dates, extensions, and estimate schedules for 2026.
Connecticut filing deadline
CT corporation business tax returns due May 15 for calendar-year filers.
Due: May 15, 2026
Extension: Nov 15, 2026
Form: Form CT-1120
Estimated payments
Estimated payment dates: Apr 15, 2026, Jun 15, 2026, Sep 15, 2026, Dec 15, 2026.
Due: Apr 15, 2026
FAQ
Does Connecticut require C Corporation estimated payments?
Estimated payments are scheduled for Apr 15, 2026, Jun 15, 2026, Sep 15, 2026, Dec 15, 2026.
Where can I file Connecticut C Corporation taxes?
Use Connecticut Department of Revenue Services resources at https://portal.ct.gov/DRS for forms and filing instructions.