CT-1120: Corporation Business Tax Return (2025)
Connecticut · Connecticut DRS · Used for tax years 2025
Form CT-1120 is Connecticut’s 2025 Corporation Business Tax Return. It reports net income, calculates tax on net income and minimum tax on capital, and accounts for tax credits and payments to determine the balance due or overpayment.
What you'll need
Attach these documents:
- A complete copy of federal Form 1120, including all schedules as filed with the IRS.
- A schedule listing corporate officers’ names, titles, and addresses.
Depending on your answers and entries, the form also calls for:
- Schedules supporting surplus reserves and holdings of stock of private corporations.
- An explanation for amounts on Schedule D, Line 9.
- A list of addresses for all Connecticut real property transferred if you answer Yes to Schedule G, Question 2(a) or 2(b).
- An explanation if IRS audit adjustments were not reported to Connecticut.
- A copy of the IRS notification or federal Form 1120X, as applicable, when amending for federal adjustments.
- An explanation of any claimed Connecticut Corporation Business Tax exemption, including the statutory citation.
- Form CT-1120I if you used the annualized method to calculate estimated tax installments.
- Form CT-1120AB if you answer Yes to the related-member expense question on page 4.
Have your FEIN, Connecticut Tax Registration Number, federal return figures, and tax payment records available. For direct deposit, have your bank routing and account numbers ready.
How to file
File electronically. Do not mail a paper return to the Connecticut Department of Revenue Services (DRS). The form directs you to portal.ct.gov/DRS for more information.
- Complete Schedules A, B, D, E, and G before completing Schedule C.
- Complete the corporate officer’s signature and contact information fields, along with paid preparer information if applicable.
- Attach the required supporting documents and keep a copy of the return for your records.
- File Form CT-RSLP separately if requesting a refund for the Student Loan Payment tax credit.
- File Form CT-1120 XCH separately if exchanging research and development tax credits.
Common mistakes
- Using the wrong year’s form: DRS says forms are year specific. Use the 2025 form for tax year 2025 to avoid processing delays.
- Mailing a paper return: This return must be filed electronically. The form also says not to use staples.
- Completing Schedule C too soon: Complete Schedules A, B, D, E, and G first.
- Exceeding printed limits: Schedule A, Line 4 must not exceed 50% of Line 3. Schedule C, Line 5a must not exceed Line 4.
- Including penalty and interest on an amended return’s Line 9d: The form specifically says to exclude them.
- Forgetting your records: Keep a copy of the return.
Questions people ask
What is the minimum tax shown on the form?
Schedule C lists a $250 minimum tax. On Line 1a, enter the greatest of Schedule A, Line 6; Schedule B, Line 6; or $250.
When does the form tell me to enter zero for the surtax?
Enter zero on Schedule C, Line 1b if federal Form 1120, Line 11 is less than $100,000,000 or Schedule C, Line 1a is $250. Otherwise, Line 1b directs you to multiply Line 1a by 10%.
Can I apply an overpayment to next year’s estimated tax?
Yes. The 2025 form provides Line 12a for an amount credited to 2026 estimated tax and Line 12b for an amount refunded.
How can I get a faster refund?
The form recommends direct deposit. Complete Lines 12c, 12d, and 12e with the account type, routing number, and account number. It also asks whether the refund will go to a bank account outside the U.S. and requests the bank name.
Where can I check whether I should file Form CT-1120CU instead?
Form CT-1120 directs you to the DRS website to check whether you should file Form CT-1120CU. The website printed on the form is portal.ct.gov/DRS.