CT-1120K: Business Tax Credit Summary (2025)
Connecticut · Connecticut DRS · Used for tax years 2025
Form CT-1120K summarizes Connecticut business tax credits for the 2025 income year. It reports credits claimed and applied to corporation business tax or other taxes, along with carrybacks, carryforwards, refunds, exchanges, and credits shared with unitary affiliates.
Who files this form
Attach Form CT-1120K to Form CT-1120 or the applicable tax return whenever you claim credits from the current income year or have credit carryforward balances from a prior year.
This requirement applies to returns for these Connecticut taxes:
- Corporation business tax.
- Unrelated business income tax.
- Air carrier tax.
- Railroad companies tax.
- Community antenna television system companies tax.
- Utility companies tax.
- Public service companies tax.
- Petroleum products gross earnings tax.
Each member included in a combined unitary return, Form CT-1120CU, that claims, applies, or shares a credit must file a separate Form CT-1120K.
Insurance and health care tax filers use Form CT-207K for the taxes specified in the instructions. Personal income tax filers use Schedule CT-IT Credit instead.
What you'll need
Have the following forms and information available:
- Your corporation name and Connecticut Tax Registration Number. Form CT-1120CU filers also provide a member number.
- Form CT-1120, Form CT-1120CU, or the other tax return to which the credits apply.
- The applicable credit forms listed beside the credits you claim, such as Form CT-1120RC for Research and Experimental Expenditures or Form CT-1120EDPC for Electronic Data Processing Equipment Property Tax.
- Your 2025 credit amounts, prior-year carryforward balances, and amounts applied, carried back, carried forward, exchanged, or refunded, as applicable.
- For combined unitary filers, amounts of credits received from or shared with unitary affiliates.
If claiming credits against more than one tax type, attach a separate Form CT-1120K and the applicable credit forms to each return.
How to file
Electronically: File Form CT-1120K through myconneCT when filing Form CT-1120.
By mail: Complete the form in blue or black ink only. Do not use staples. Attach it to Form CT-1120 or the applicable tax return. The supplied text does not give a mailing address.
Use the 2025 form for the 2025 income year. Complete the applicable credit categories in Part I, then use Part II for credits applied to Corporation Business Tax or Part III for credits applied to other taxes.
Transfer Part II, Line 9 to Form CT-1120, Schedule C, Line 5a, or the appropriate column of Form CT-1120CU, Part II, Line 3. Refundable credits and excess credit utilization have separate transfer instructions on the form.
For Part III, enter the name of the tax and transfer Line 11 to the appropriate return. If applying credits to more than one tax other than Corporation Business Tax, attach supplemental copies of Part III.
Common mistakes
- Using the wrong year's form. The correct year's form must be submitted to avoid processing delays.
- Claiming the same credit more than once. The instructions expressly prohibit this.
- Ignoring credit order or limits. Follow the required order and each line's limit. Claim carryforwards that expire first before those that expire later or do not expire.
- Including exchanged research credits in the wrong total. Do not include Part I-C, Lines 2 and 3, Column G amounts in the Column G total on Line 15.
- Skipping Part I-A for certain housing credits. Complete Part I-A first when claiming Housing Program Contribution or Workforce Housing Opportunity Development credits in Part I-C.
- Using affiliate-sharing columns when not filing a combined unitary return. These columns are only for Form CT-1120CU filers.
Questions people ask
Do I need this form if I only have unused credits from an earlier year?
Yes. Form CT-1120K must be attached to the applicable return when prior-year carryforward credit balances exist, even if you are not claiming a current-year credit.
In what order do I apply Corporation Business Tax credits?
Apply credits with carryback provisions first, then credits with neither carryback nor carryforward provisions, then credits with carryforward provisions. Apply the Electronic Data Processing Equipment credit after those categories. Refundable credits come last.
How much Corporation Business Tax can credits offset?
The standard limit is 50.01% of tax due before credits. Remaining Research and Development, Research and Experimental Expenditures, and qualified Human Capital Investment credits may increase total credit use to 70% of tax liability. Remaining University of Connecticut Incentive Program credits may increase total credit use to 100%. Only refundable credits may be applied beyond the tax liability.
How do I claim a credit carryback?
For credits in Part I-A, apply the credit to the current year's tax first. A remaining balance may be claimed against a preceding year's tax by filing Form CT-1120X or the appropriate amended tax return, subject to the credit's carryback provisions and expiration.