If you're starting a corporation, LLC, or limited partnership, your official business name will be automatically registered when you file your articles of incorporation, articles of organization, or statement of limited partnership with your state filing office. However, if you will sell products or services under a different name, you must also file a fictitious name statement (sometimes called an "assumed" name statement) with the state or county where your business is headquartered. For more information on how to register a fictitious name, see Registering Your Business Name.
Other types of businesses may also have to comply with fictitious or assumed business name requirements. Generally, any business that doesn't use its legal name as part of its business name must file a fictitious name statement with a government agency, usually the county clerk's office. For more information on how to register a fictitious name, see Registering Your Business Name.
You may also want to take advantage of the extra protection that registering your name as a trademark can give you. While it's not required, registering your name as a trademark at the state and/or federal level can prevent other businesses from using a name that's likely to be confused with your business name. For more information, see Filing a Federal Trademark Application FAQ.