Key figures
Connecticut compliance
2026, with sources
Registering and staying registered
A Delaware corporation doing business in Connecticut files an Application for Certificate of Authority online at Business.CT.gov: $385, which includes a $285 license fee. From then on it files an annual report each year by the last day of the anniversary month of its registration, $435 for a foreign stock corporation, and can file up to a month early. The Secretary of the State emails a reminder about a month before it is due.
That $435 is high next to most states, and a startup registered in Connecticut and two neighbors pays more in annual report fees there than anywhere else. LLCs follow a different calendar: their annual reports are due between January 1 and March 31.
The tax calendar
The corporation business tax return is due on the 15th day of the fifth month after year end (May 15 for a calendar year), a month after the federal Form 1120, except for June 30 year ends, which are due on the 15th day of the fourth month. Form CT-1120 EXT extends filing to the 15th day of the eleventh month. Every return is filed electronically.
Estimated payments are front-loaded: the first installment on the 15th day of the third month is 30% of prior-year tax (including surtax), the second brings the total to 70%, then 80%, then 100% by the 15th day of the twelfth month. A company that just turned profitable should expect a March payment of nearly a third of last year’s tax.
Information returns and unclaimed property
Connecticut collects state copies of Forms 1099-NEC and 1099-MISC directly, due January 31 with Form CT-1096 through myconneCT, and requires electronic filing once you have 25 or more. Unclaimed property, from uncashed vendor checks to customer credit balances, is reported to the Office of the Treasurer by March 31, after due diligence letters to owners.
Deadlines
- By the last day of the anniversary month of registration$435 for a foreign stock corporationAnnual report
- May 15 for calendar yearsCorporation business taxForm CT-1120 / CT-1120CU
- Jan 31State copies of 1099-NEC and 1099-MISCForms 1099 / CT-1096
- Mar 31Unclaimed property report and remittance
The federal baseline
This page covers what Connecticut adds. The federal rules underneath it apply here too.
Common questions
What does it cost to keep a Delaware corporation registered in Connecticut?
A foreign stock corporation pays $385 to register (a Certificate of Authority, including a $285 license fee) and $435 a year for its annual report, which is due by the last day of the anniversary month of its registration. Combined with Delaware’s franchise tax, Connecticut is one of the more expensive states to stay registered in.
When is the Connecticut corporate return due?
On the 15th day of the fifth month after year end, May 15 for a calendar-year company, a month after the federal return. An extension runs to the 15th day of the eleventh month, but tax is due on the original date.
Compliance next door
- MAMassachusetts complianceRegistering costs $400; the annual report is $125 ($100 online) and due 2½ months after year end, not on an anniversary. The excise return is due April 15 and unclaimed property November 1.
- NYNew York complianceQualifying in New York is cheap ($225, then $9 every two years). The calendar is not: state and city returns on April 15, March mandatory first installments, and a March 10 unclaimed funds report.
- RIRhode Island complianceRhode Island charges $150 to register and $50 for an annual report filed February 1 to May 1. The RI-1120C is due April 15, and unclaimed property before November 1.
More of the Connecticut guide
- AccountingAccounting and state tax in ConnecticutCorporate tax, conformity to federal rules, apportionment and what it does to your books
- ReceivablesReceivables and sales tax in ConnecticutSales tax registration, economic nexus, whether SaaS is taxable, and collecting from customers
- PayablesPayables and contractors in ConnecticutPaying vendors and contractors: 1099 filing, use tax, contractor tests and withholding
- PayrollPayroll taxes and employer rules in ConnecticutWithholding, unemployment insurance, paid leave, minimum wage and the rules on paydays
- AdvisoryAdvisory: credits and decisions in ConnecticutCredits, incentives and the decisions that are cheaper to get right the first time
Sources
Checked against each agency’s own page on . Rates and thresholds change, usually on January 1.
General information for US companies, not tax, legal or accounting advice for yours. Rules and thresholds change; confirm the specifics with a CPA or the agency before you act on them.