Connecticut Business Tax Deadlines (2026)
Next: June 15, 2026 — Federal & Connecticut Q2 Estimated Tax Payment
Next Deadline: June 15, 2026 — Federal & Connecticut Q2 Estimated Tax Payment
Federal Tax Deadlines (2026)
| Form | Who Files | Due Date | Extension Deadline |
|---|---|---|---|
| Form 1040 (Schedule C) | Sole proprietors | April 15 | October 15 |
| Form 1065 | Partnerships, Multi-member LLCs | March 15 | September 15 |
| Form 1120-S | S-Corporations | March 15 | September 15 |
| Form 1120 | C-Corporations | April 15 | October 15 |
| Form 990 | Nonprofits | May 15 | November 15 |
| Estimated Taxes (Q1) | All | April 15 | — |
| Estimated Taxes (Q2) | All | June 15 | — |
| Estimated Taxes (Q3) | All | September 15 | — |
| Estimated Taxes (Q4) | All | January 15, 2027 | — |
Connecticut State Tax Deadlines (2026)
| Tax Type | Due Date | Form/Filing | Notes |
|---|---|---|---|
| Individual Income Tax | April 15 | Form CT-1040 | Rates 3%–6.99% |
| Corporate Business Tax | April 15 (or 15th of 4th month) | Form CT-1120 | 7.5% rate |
| Pass-Through Entity Tax (PET) | March 15 | Form CT-1065/CT-1120SI | Elective PET available |
| Sales Tax (Monthly) | Last day of following month | Form OS-114 | State rate 6.35% |
| Withholding Tax (Monthly/Weekly) | Varies by payroll size | Form CT-941 (quarterly reconciliation) | Employers |
| Annual Report | Anniversary month | Filed with Secretary of State | $80 fee (LLC); $435 (Corp) |
| Business Entity Tax | Repealed | — | Was $250 biennial; now repealed |
| Estimated Income Tax (Q1) | April 15 | Form CT-1040ES / CT-1120 ESA | — |
| Estimated Income Tax (Q2) | June 15 | Form CT-1040ES / CT-1120 ESA | — |
| Estimated Income Tax (Q3) | September 15 | Form CT-1040ES / CT-1120 ESA | — |
| Estimated Income Tax (Q4) | January 15, 2027 | Form CT-1040ES / CT-1120 ESA | — |
Quarterly Estimated Tax Deadlines in Connecticut
Connecticut follows the federal estimated tax payment schedule:
Estimated payments are required if you expect to owe $1,000 or more in Connecticut income tax for the year.
Connecticut-Specific Tax Requirements
Connecticut has a graduated individual income tax with rates ranging from 3% to 6.99%. The state also imposes a Corporate Business Tax at a rate of 7.5% (with a 10% surcharge in some years — check current legislation). The minimum corporate tax is $250. Connecticut offers an elective Pass-Through Entity Tax (PET) that allows S-corps and partnerships to pay tax at the entity level, providing a workaround for the federal SALT deduction cap.
Connecticut's sales tax rate is 6.35%, with a higher rate of 7.75% on certain luxury goods (vehicles over $50,000, jewelry over $5,000, etc.). There is no local sales tax — the rate is uniform statewide. The economic nexus threshold for remote sellers is $100,000 in sales and 200 transactions. Connecticut does not impose a franchise tax or gross receipts tax.
Connecticut repealed its Business Entity Tax (which was $250 biennially) in recent years. Businesses must still file annual reports with the Secretary of State — $80 for LLCs, $435 for corporations. Employers must register for withholding tax and file returns on a schedule determined by payroll size (weekly, monthly, or quarterly).
What Happens If You Miss a Connecticut Tax Deadline?
Connecticut Department of Revenue Services
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