Connecticut Tax Deadlines
State income tax filing deadlines, extensions, and estimates for 2026.
Connecticut Department of Revenue Services
https://portal.ct.gov/DRS
individual deadline
Due: Apr 15, 2026
Extension: Oct 15, 2026
Form: Form CT-1040
CT individual returns due April 15, 2026.
Estimated Payments
Sole Proprietorship deadline
Due: Apr 15, 2026
Extension: Oct 15, 2026
Form: Form CT-1040
Business income reported on CT personal return.
Estimated Payments
Partnership deadline
Due: Mar 16, 2026
Extension: Sep 15, 2026
Form: Form CT-PET / CT-1065
CT pass-through returns due March 15 (next business day if weekend).
S Corporation deadline
Due: Mar 16, 2026
Extension: Sep 15, 2026
Form: Form CT-1120SI
CT S corporation returns due March 15 (next business day if weekend).
C Corporation deadline
Due: May 15, 2026
Extension: Nov 15, 2026
Form: Form CT-1120
CT corporation business tax returns due May 15 for calendar-year filers.
Estimated Payments
LLC deadline
Due: Mar 16, 2026
Extension: Sep 15, 2026
Form: State business income tax return
Calendar-year due date follows federal timing for pass-through entities.
Nonprofit deadline
Due: May 15, 2026
Extension: Nov 15, 2026
Form: State nonprofit return
Nonprofit annual return generally due the 15th day of the 5th month.
Estimated Tax Payments
View all quarterly estimated payment due dates for Connecticut.
FAQ
Does Connecticut conform to federal due dates?
Many Connecticut deadlines follow the federal calendar. Always confirm on Connecticut Department of Revenue Services.
Where can I file Connecticut tax forms?
Visit Connecticut Department of Revenue Services at https://portal.ct.gov/DRS for official forms and e-file options.