Form CT-1040X (2023) - Amended Connecticut Income Tax Return

Form CT-1040X, also known as the Connecticut Amended Income Tax Return for Individuals, allows you to correct errors or make changes to your originally filed Connecticut income tax return for the year 2023.

When to File Form CT-1040X?

You should file Form CT-1040X (2023) if any of the following situations apply:

A. You discover an error on your original return, such as incorrectly reported income, deductions, or credits.

B. You receive new information that affects your tax liability for 2023, such as missing income statements or changes made to your federal tax return.

C. The Connecticut Department of Revenue Services (DRS) issues a notice of additional tax due or a refund.

What Changes Can You Make with Form CT-1040X?

A. Federal Changes: If your federal income tax return is amended (using Form 1040X), you need to report those changes on your CT-1040X to ensure consistency between your state and federal returns.

B. Income: You can report additional income or correct any errors related to your previously reported income.

C. Deductions and Credits: Claim additional deductions or credits you missed, or correct any mistakes in the amounts you previously claimed.

D. Filing Status: Change your filing status if necessary (e.g., from single to married).

Key Points to Remember About Form CT 1040X:

Filing Instructions:

  • The form is available in both paper and electronic formats.
  • Download the Form CT 1040X attached below.
  • You can file electronically through the DRS website or through authorized tax preparation software.
  • Be sure to attach all necessary documentation to support any changes you are making on your amended return.


Generally, you have 3 years from the original due date of your tax return (including extensions) to file Form CT-1040X. However, specific exceptions may apply. It's recommended to consult the DRS website or a tax professional for the most up-to-date deadlines.

For the current year's Form CT 1040X, click here.