Connecticut State Income Tax Overview

If you earned income from a Connecticut-based business or you were a resident of Connecticut during the most recent tax year, you will likely need to file a state income tax return for Connecticut.  Connecticut state income tax is overseen by the Connecticut Department of Revenue Services and is a separate tax return from the federal income tax return that must be filed with the Internal Revenue Service.

Information about the Connecticut state income tax return follows.  If you need additional information about filing a federal income tax return, see our “Tax Relief” page.

Who does Connecticut require to file a state income tax return?

Who has to file a Connecticut state income tax return depends on your residency during the tax year and the amount of gross income you earn.

Residents

If you are a resident of Connecticut for the entire year, you must file a state income tax return if your gross income for the tax year exceeds the following minimum threshold:

  • $12,000 and you are filing separately
  • $13,000 and you are filing single
  • $19,000 and you are filing head of household
  • $24,000 and you are filing jointly or qualifying widow(er) with dependent child

Part-Year Residents

If you are a resident of Connecticut for only part of the year, then your income taxed for Connecticut state income tax is divided into two categories.  During the part of the year when you were a resident of Connecticut, all of your income is considered for state income tax purposes.  During the part of the year when you were not a resident of Connecticut, only your income earned from a Connecticut-based source is considered for state income tax purposes.

Non-Residents

A non-resident must file a Connecticut income tax return if any of the following is true for the tax year:

  • Connecticut income tax was withheld from your wages or other payments
  • You made estimated payments of income tax to Connecticut
  • You meet the gross income test and had any income (or loss) from Connecticut sources
  • You were required to pay the federal alternative minimum tax

A non-resident meets the gross income test if his total income for the year from all sources, both those from a Connecticut source and those outside of Connecticut, exceeds the following:

  • $12,000 and you are filing separately
  • $13,000 and you are filing single
  • $19,000 and you are filing head of household
  • $24,000 and you are filing jointly or qualifying widow(er) with dependent child

What tax rate is used to calculate my Connecticut state income tax?

Connecticut uses a marginal tax rate to calculate state income tax.  Connecticut tax rates are outlined in the table below:

Tax Rate Connecticut Taxable Income
Married Filing Jointly Single, Married Filing Separately Head of Household
Over But Not Over Over But Not Over Over But Not Over
3.0% $0 $20,000 $0 $10,000 $0 $16,000
5.0% $20,000 $100,000 $10,000 $50,000 $16,000 $80,000
5.5% $100,000 $200,000 $50,000 $100,000 $80,000 $160,000
6.0% $200,000 $400,000 $100,000 $200,000 $160,000 $320,000
6.5% $400,000 $500,000 $200,000 $250,000 $320,000 $400,000
6.7% Over $500,000 Over $250,000 Over $400,000

Can I file an extension of my Connecticut state income tax return?

Connecticut state income taxes are normally due on April 15 of each tax year, or if April 15 falls on a holiday or a weekend, the first non-holiday business day thereafter.  If you need additional time to complete your state income tax return, you can obtain a six-month extension.

A six-month extension is automatically accepted if you have received an extension on your federal income tax return.  If you have not received an extension of your federal income tax return, you must demonstrate a good reason to receive an extension on your state income tax return.

Note that an extension of your Connecticut state income tax return is only for the filing of your tax return, not for payment of any tax due.  You must still remit payment of any estimated tax due by the original April filing date or you will be assessed penalties and interest on the unpaid amount.

Can I obtain help with my Connecticut state income tax return?

Yes, assistance is available to answer questions about or help you prepare your Connecticut state income tax return.  If you call the number at the top of this page, a tax attorney who is experienced working with Connecticut state income tax law will contact you to provide help.

by Mark Johnston

Mark has been a contributor to legal web sites related to bankruptcy, tax, and criminal law since 2011. He has an Accounting degree from Texas A&M University.