If you choose to do business under a different name from the one on your tax returns, you will have to file for a trade name certificate. You file a trade name certificate with the town clerk in the town where you do business, not with the Secretary of the State. This is known as the "doing business as" option.
You can find your local town clerk here in this handy Connecticut town clerks directory.
Corporations and Limited Liability Companies can also function under trade names, but if they're doing business under the name registered with our office they don't need to file a trade name with the town clerk.
For example, if you are "Green Landscaping LLC" you don’t need to register a trade name if you’re conducting business as "Green Landscaping LLC". But if you wish to do business under a different name, then you will have to file a trade name with the town clerk.