Go to the website of the secretary of state or other equivalent office, which handles the formation of LLCs in the state where you will organize your LLC. Many states will have a search feature on their websites that allows you to perform an online search for the name of an existing LLC by entering the name into the appropriate field. If your name doesn't appear after your search, then that is a good indicator that the name has not already been used in your state.
Call or email the secretary of state's office in the event that its website doesn't have search capabilities, or to confirm your findings from your web search. Both phone and email contact information should be located on the website. The office should confirm whether or not your chosen name has been used.
File a name reservation request with the secretary of state's office in your state in the event you are not immediately forming the LLC, yet want to make sure the name remains available. Upon receipt of the name reservation request, the secretary of state will check to make sure the name is not currently in use and, if not, will hold the name for your business for a specified period of time, depending on state law. This will assure that your chosen name is available and does not get taken by another company between the reservation time and the date you actually form your LLC.
Check with each secretary of state’s office to make sure your current LLC name is available in all states in which you desire to register to do business as a foreign LLC. In the event your business name is already being used in that state, your LLC’s manager will be required to submit a statement or file an appropriate resolution adopting an available fictitious name to use when transacting business in that state as a foreign LLC.