Connecticut C corporation compliance calendar 2027: the filings and due dates

Each filing, in plain English

Connecticut annual withholding reconciliation

When: by January 31 each year. Where: Connecticut Department of Revenue Services.

Connecticut withholds state income tax from employee wages, and the employer reconciles the year's withholding with the Connecticut Department of Revenue Services after year end, by January 31 in most states and the end of February in a few, with copies of the W-2s where the state takes them. Withholding deposits during the year follow a schedule the state assigns, monthly or quarterly for most small employers. A payroll provider normally handles both.

Connecticut harassment prevention training (3 or more employees)

When: by January 31 each year. Where: Connecticut labor and civil rights agencies.

Connecticut requires private employers to train employees on preventing sexual harassment. Two hours for all employees within six months of hire, for employers with three or more employees (supervisors only below three), with a refresher every ten years. The date here is a planning reminder at the start of the year; the legal timing runs from each employee's hire date and the last training.

Connecticut Paid Leave contributions

When: by the last day of the 1st month after each quarter. Where: Connecticut Paid Leave Authority. If missed: Interest and late penalties set by the program on premiums paid late.

Connecticut Paid Leave is funded by an employee deduction of 0.5% of wages, no employer share, which the employer withholds and remits every quarter through the Paid Leave Authority's portal. The rate is set by the program each year, so the figure on the agency page is the one to use, and a payroll provider normally files the report.

Connecticut unemployment insurance wage report

When: by the last day of the 1st month after each quarter. Where: Connecticut unemployment insurance agency. If missed: Late filing and payment penalties set by the state, plus loss of the federal FUTA credit if contributions are not paid on time.

An employer registers for unemployment insurance in each state where it has employees and files a wage report every quarter, by the last day of the month after the quarter in nearly every state: April 30, July 31, October 31 and January 31. The contribution rate is set by the state each year. Paying on time also earns the 5.4% credit against the federal unemployment tax.

Annual federal unemployment tax return

When: by January 31 each year. Where: IRS (Form 940). If missed: 5% of the unpaid tax for each month late, up to 25%.

Federal unemployment tax is an employer only tax of 6% on the first $7,000 paid to each employee, reduced to 0.6% for employers that pay state unemployment tax on time. Form 940 reports it once a year, by January 31. Quarterly deposits are due during the year once the liability passes $500. An organization exempt under section 501(c)(3) owes no federal unemployment tax and files no Form 940; other exempt organizations, such as 501(c)(4) and 501(c)(6) groups, do.

Quarterly federal payroll tax return

When: by the last day of the 1st month after each quarter. Where: IRS (Form 941). If missed: 5% of the unpaid tax for each month late, up to 25%, plus failure to deposit penalties of 2% to 15%.

Nearly every employer files Form 941 four times a year, by the last day of the month after each quarter: April 30, July 31, October 31 and January 31. It reconciles what was withheld from employees and what the employer owes in Social Security and Medicare tax against the deposits already made. The smallest employers, those the IRS has told to file Form 944 because their annual liability is $1,000 or less, file once a year by January 31 instead. A payroll provider normally files it; the company is still the one liable.

W-2 forms to employees and the SSA

When: by January 31 each year. Where: Social Security Administration (Forms W-2 and W-3). If missed: $60 to $340 per form depending on how late (the figures for forms due in 2026, adjusted yearly), with no cap for intentional disregard.

Employees need their W-2 to file their own taxes, so the deadline is early: January 31, both for the copy to the employee and the copy to the Social Security Administration. Penalties are per form and grow the longer the forms are late. Payroll providers prepare and file these as part of year end.

Connecticut corporate estimated tax payment

When: on the 15th day of the 4th, 6th, 9th, 12th months of the fiscal year (April 15, June 15, September 15, December 15 for a calendar year). Where: Connecticut Department of Revenue Services (The state's estimated tax voucher or online payment). If missed: Underpayment interest, and in some states a penalty, on each short installment.

Like the IRS, Connecticut collects corporate income tax during the year once the expected tax passes a threshold the state sets (a few hundred to a thousand dollars in most states). The installments fall on the 15th day of the fourth, sixth, ninth and twelfth months of the fiscal year in most states, the same days as the federal ones; the Connecticut Department of Revenue Services page has the threshold and any state that differs. Shown for every C corporation because the threshold is low; a corporation expecting no state tax can mark the lines handled.

Corporate estimated tax payment

When: on the 15th day of the 4th, 6th, 9th, 12th months of the fiscal year (April 15, June 15, September 15, December 15 for a calendar year). Where: IRS (Estimated tax worksheet in the Form 1120 instructions, paid through EFTPS). If missed: An underpayment penalty computed on Form 2220, charged as interest for each day the installment is short.

A C corporation that expects to owe $500 or more pays its income tax in four installments during the year, on the 15th day of the fourth, sixth, ninth and twelfth months of its fiscal year. For a calendar year that is April 15, June 15, September 15 and December 15; a June 30 fiscal year pays October 15, December 15, March 15 and June 15. The dates here follow the fiscal year you gave.

Federal corporate income tax return

When: by the 15th day of the 4th month after the fiscal year ends (April 15 for a calendar year). Where: IRS (Form 1120). If missed: 5% of the unpaid tax for each month late, up to 25%, plus interest.

A C corporation files its own income tax return on Form 1120 by the 15th day of the fourth month after its fiscal year ends, which is April 15 for a calendar year. An extension on Form 7004 gives six more months to file, but the tax itself is still due on the original date.

Connecticut corporate income tax return

When: by the 1st day of the 5th month after the fiscal year ends (May 1 for a calendar year). Where: Connecticut Department of Revenue Services.

Connecticut taxes corporate income, so a C corporation doing business there files a state return with the Connecticut Department of Revenue Services by the 1st day of the 5th month after the fiscal year ends (May 1 for a calendar year), later than the federal Form 1120. The state usually honors a federal extension to file, but not to pay. The form name and any minimum tax are on the state's site.