A fictitious business name is an official business name registration that allows sole proprietorships (individuals), partnerships, and even corporate entities to conduct business under a business name other than their true legal name. Depending on the state or local jurisdiction, "Fictitious Business Names" (FBN) registrations are often referred to as "Doing Business As" (DBA), "Assumed Names", or "Trade Names." Some states allow for the filing of fictitious business names at the state level, other states require that these registrations be filed at the local level, and a few states do not recognize fictitious business names at all. In many jurisdictions, the fictitious business name filing must be followed by a publication of the registration in an authorized manner such as an approved newspaper. It is also important to know the duration of these registrations, as some must be renewed frequently while others may never expire.

Any type of entity can file a fictitious business name, however there are some restrictions. A sole proprietorship or partnership cannot add a corporate indicator to the fictitious business name, such as Inc. or LLC. A corporate entity can only use the corporate indicator actually associated with the legal entity, thus an LLC cannot use a fictitious business name with a corporate indicator of Inc.