Use the U.S. Patent and Trademark Office’s trademark search tool to determine whether or not a business name as been trademarked. Individual states also offer tools to determine if a business name is on file with the state.
The office that tracks business names varies between states. For example, in California, inquiries about name availability are submitted to the Secretary of State's office, while in New York state inquiries are processed by the Division of Corporations. Though states retain a database of names in use, final availability of names can only be determined by submitting a form to the appropriate office. A small fee is usually associated with each inquiry.