Corporation Business Tax
Who Must File
The Corporation Business Tax is a tax imposed on businesses that file as C corporations for federal income tax purposes.
If your corporation carries on business or has the right to carry on business in Connecticut, you may have to file an annual Connecticut Corporation Business Tax Return.
Certain companies are exempt from the Corporation Business Tax.
In addition to any tax filing obligations, your company may also be required to register with the Connecticut Secretary of the State as referenced in Connecticut Agencies Regulations 12-214-1.
Carrying on business includes:
- Owning or leasing (as lessee) real property
- Maintaining an office
- Selling tangible personal property
- Performing or soliciting orders for services
- Selling or soliciting orders for real property
- Maintaining a stock of inventory in a public warehouse
- Delivering merchandise inventory on consignment to its distributors or dealers
- Owning or leasing (as lessee) personal property which is not related to solicitation of orders
- Participating in the approval of servicing distributors and dealers where its customer or user of its product can have such product serviced or repaired.
Having the right to carry on business means:
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For companies incorporated or organized under the laws of this state, the Secretary of the State has endorsed its certificate of incorporation.
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For companies incorporated or organized under the laws of another state, the Secretary of the State has issued to it a certificate of authority.
Economic Nexus
If your company has a substantial economic presence in Connecticut, it must file a Corporation Business Tax return. IP 2010(29.1), Q & A on Economic Nexus.
In addition to any tax filing obligations, your company may also be required to register with the Connecticut Secretary of the State.
What return to file
You must file Form CT-1120, Corporation Business Tax Return, unless your corporation engages in a unitary business with other commonly owned corporations.
If your corporation engages in a unitary business with other commonly owned corporations, you must file Form CT-1120CU, Combined Unitary Corporation Business Tax Return. See SN 2016(1),Combined Unitary Legislation, for more information.
When are returns due
Your Connecticut return is due on the fifteenth day of the month following the due date of the federal return. The due date generally will be the fifteenth day of the fifth month after the end of your corporation’s year. For example, if your corporation has a December 31st year end, the return is due on May 15th.
Exception for June 30th year ends: If your corporation has a June 30th year end, the return is due on October 15th.
| Year End | Original Due Date | Extended Due Date |
| Anything except June 30 | 15th day of 5th month after year end | 15th day of 11th month after year end |
|
June 30 |
15th day of 4th month after year end |
15th day of 11th month after year end |
I made a Corporation Business Tax Extension payment on the TSC before the due date. Do I still have to file the form or is the payment sufficient to get the extension approved?
Yes, you must also file Form CT-1120 EXT, Application for Extension of Time to File Corporation Business Tax Return.
How to file and pay online (TSC)
You are required to file your Corporation Business Tax Return and make payments electronically. Payments and Form CT-1120 may be filed through the Taxpayer Service Center (TSC).
If you cannot file and/or pay electronically, you should request a waiver by filing Form DRS-EWVR.
If your corporation’s tax liability, after credits, will exceed $1,000, you must make quarterly estimated payments. Estimated payments are due on the 15th day of the 3rd, 6th, 9th and 12th months of the year (March, June, September and December if your corporation has a December 31st year end).
How to register your business
Corporations that are required to file a Corporation Business Tax Return must register with DRS by completing the appropriate section of Form REG-1, Business Taxes Registration Application. There is no fee for registering for the Corporation Business Tax.
If the corporation elects S corporation status with the Internal Revenue Service after it registers for Corporation Business Tax, it must notify DRS of the change in its status by filing an amended Form REG-1, Business Taxes Registration Application.
Amended Returns and IRS Changes
To amend your Form CT-1120, Corporation Business Tax Return, or Form CT-1120U, Unitary Corporation Business Tax Return, use Form CT-1120X, Amended Corporation Business Tax Return.
To amend your Form CT-1120CR, Combined Corporation Business Tax Return, or Form CT -1120CU, Combined Unitary Corporation Business Tax Return, check the “Amended” box on the front of the Form CT-1120CR or Form CT-1120CU and file the return as amended.
Select the appropriate return at Forms and Instructions.