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IP 92(5.7)

Estimated Connecticut Income Taxes

This Informational Publication has been replaced by IP 92(5.8)

PURPOSE: This publication explains requirements for paying estimated income tax. Connecticut taxpayers can be charged interest for underpaying their estimated income tax, even though they pay all the Connecticut income tax they owe by the April 15 filing deadline. Connecticut law requires taxpayers to pay Connecticut income tax during the year, through withholding or estimated tax payments. Most employees have these taxes automatically withheld from their paychecks. If you are self-employed, receive a pension or annuity, or are receiving unemployment compensation and have not elected Connecticut income tax withholding, or you receive any other income from which Connecticut income tax is not withheld, you should probably be making estimated income tax payments.

WHAT IS ESTIMATED TAX? Because it is difficult to determine your exact tax liability before the end of the year, you make estimated tax payments during the year based upon what you expect to earn in the current year or based upon what you actually earned in the prior year. When you file your annual income tax return, you report your estimated tax payments. If you have overpaid your estimated tax during the year, you will receive a refund. If you have underpaid your taxes during the year, you will have to pay the tax you owe and you may have to pay interest on the amount of the underpayment.

WHO SHOULD PAY ESTIMATED TAX? In most cases, you must make estimated payments of Connecticut income tax if you expect to owe, after subtracting your Connecticut income tax withholding, more than $500 for the taxable year, after tax credits, if any, are taken into account, and you expect your withholding to be less than your required annual payment.

WHAT IS MY REQUIRED ANNUAL PAYMENT? Your required annual payment is the lesser of:

  • 90% of the total income tax shown on your current year Connecticut income tax return; or
  • 100% of the total income tax shown on your preceding year Connecticut income tax return, if you filed a Connecticut income tax return for the preceding taxable year that covered a 12-month period.

NOTE: You do not have to make estimated income tax payments if you did not file a Connecticut income tax return for the preceding taxable year because you had no Connecticut income tax liability and you were either:

  • a resident of Connecticut for the entire preceding taxable year;
  • a nonresident or part-year resident of Connecticut with Connecticut source income.

INCOME NOT SUBJECT TO WITHHOLDING: The checklist below includes many (although not all) of the types of income that are not subject to Connecticut income tax withholding and that may require you to pay estimated tax:

pensions and annuities (if no Connecticut income tax is withheld); unemployment compensation (if no Connecticut income tax is withheld);
gambling winnings (if no Connecticut income tax is withheld); prize winnings;
self-employment; capital gains;
interest income; dividend income;
rental income; federally taxable social security income.

To avoid the filing of estimated tax, you may request your employer or pension plan payer to withhold additional amounts from your wages or pension income to cover the taxes on other income. You can make this change by providing your employer or pension payer with a revised Form CT-W4 or Form CT-W4P.

Retired federal civil service employees must contact the U.S. Office of Personnel Management at 1-800-409-6528 to start, stop or make changes to Connecticut income tax withholding.

HOW DO I ESTIMATE MY TAX? To calculate your estimated tax payments, you will need Form CT-1040ES, Estimated Connecticut Income Tax Payment Coupon for Individuals. The instructions include a worksheet for computing your estimated tax payments, exemption and credit tables, and a coupon to be mailed with your estimated payments.

NOTE: If you made estimated Connecticut income tax payments last year, you will receive estimated income tax payment coupons by mail in January. The coupons are preprinted with your name, address and social security number to ensure that your payments are properly credited. If you did not make estimated payments last year, use Form CT-1040ES included in your Connecticut income tax booklet or available from the Department. (See Forms and Publications.) If you file this form, additional coupons will be mailed to you.

WHEN DO I PAY MY ESTIMATED INCOME TAX?  Generally, you must make your first estimated income tax payment by April 15. You can pay all of your estimated tax with the first payment or pay the tax in four installments, due April 15, June 15, September 15, and January 15. (Taxpayers who are not calendar year filers should use the same filing dates as they do for federal income tax purposes.) If any due date falls on a Saturday, Sunday or legal holiday, the next business day will be the due date. An estimate will be considered timely-filed if received, or if the date shown by the U.S. Post Office cancellation mark, is on or before the due date.

HOW MUCH SHOULD I PAY WITH EACH INSTALLMENT? In general, you are required to pay 25% of your required annual payment with each installment. Your installments should be made as follows:

April 15 25%
June 15 25%
(a total of 50% of your required annual payment should be paid June 15.)
September 15. 25%
(a total of 75% of your required annual payment should be paid by this date.)
January 15 25%
(a total of 100% of your required annual payment should be paid by this date.)

SPECIAL RULES FOR FARMERS AND FISHERMEN: If you are a farmer or fisherman (as defined in Section 6654(i)(2) of the Internal Revenue Code) who is required to make estimated income tax payments, you will be required to make only one payment. Your installment is due on or before January 15 following the end of the taxable year. The required installment shall be the lesser of 66 % of the Connecticut income tax shown on your current year’s return or 100% of the Connecticut income tax shown on your prior year’s return. For further information, request IP 97(8.1), Farmer’s Guide to Sales and Use and Estimated Income Taxes.

WHAT IF MY INCOME VARIES DURING THE YEAR? If you do not earn your income evenly throughout the year, you may benefit from using the annualized income installment method. Instead of paying your required annual payment in four equal installments, you may be able to reduce or eliminate the amount of one or more installments. You will make up the difference by making a larger payment for the period or periods when more of your income is earned. For information about this method, request a copy of IP 93(6.4), A Guide to Calculating Your Annualized Estimated Income Tax Installments and Worksheet CT-1040AES.

NOTE: If your estimated installment payments are based on the annualized income installment method, you must check Box D, Part I, Form CT-2210, Underpayment of Estimated Income Tax by Individuals Trusts and Estates, attach it to your income tax return, and check the Form CT-2210 box located on your Connecticut income tax return below the Name and Address section. By following this procedure, you will notify the Department that your estimated income tax is not underpaid and is not subject to interest charges.

WHAT HAPPENS IF I UNDERESTIMATE MY TAX? If you are required to make estimated income tax payments and you do not pay enough tax during the year through withholding or estimated tax payments, or if you do not make the payments on time, interest may be charged. Interest is calculated separately for each installment from the due date of that installment until the earlier of the following dates: April 15 or the date on which the underpayment is paid. (You may owe interest for an earlier installment even if you paid enough to make up the underpayment with a later installment.) Interest of 1% per month or fraction thereof will apply to the underpayment(s). If you file your income tax return for the taxable year on or before January 31 of the following year and pay the amount computed on the return as payable for the taxable year, no interest will apply for failure to make the fourth required installment. (Farmers and fishermen: refer to Special Rules for Farmers and Fishermen for required installment rules.)

MAY I APPLY AN OVERPAYMENT IN THE PRIOR YEAR TO THE NEXT YEAR'S ESTIMATE? When you file a final return for the year, you may request that overpayments of Connecticut income tax be applied to your next year’s estimated tax. If you file your Connecticut income tax return on or before April 15 (or if you file a timely request for extension of time to file and your income tax return is filed within the extension period) the overpayment will be treated as estimated tax paid on April 15. Your request to apply overpayments to next year’s estimated income tax is irrevocable.


Request the most current edition of the following publications and forms.

  • Form CT-1040ES, Estimated Connecticut Income Tax Payment Coupon
  • IP 92(9.5), Is My Connecticut Withholding Correct?
  • IP 93(6.4), A Guide to Calculating Your Annualized Estimated Income Tax Installments and Worksheet CT-1040AES
  • IP 97(8.1), Farmer’s Guide to Sales and Use and Estimated Income Taxes
  • Form CT-W4, Employee's Withholding or Exemption Certificate
  • Form CT-W4P, Withholding Certificate for Pension or Annuity Payments

FOR FURTHER INFORMATION: If you have questions about Connecticut taxes, please call the Department of Revenue Services during business hours, Monday through Friday:

  • 860-297-5962 (Hartford calling area or from out-of-state); or
  • 1-800-382-9463 (toll-free from within Connecticut)

Telecommunications Device for the Deaf (TDD/TT) users only, please call 860-297-4911 during business hours


You may obtain forms and publications at any hour, seven days a week:

  • Telephone: use the phone numbers listed above and select Option 3 from a touch-tone phone;
  • Internet: preview and download forms from the DRS Web site:

IP 92(5.7)
Income Tax
Issued: 1/23/98
Replaces: IP 92(5.6) issued 12/19/96