Maritime Mobile Service Identity


Any boater could face a sudden situation caused by a fire, collision, capsize, sinking boat or medical emergency.  With a registered VHF DSC-compatible radio using your unique MMSI number, your emergency situation is immediately transmitted with critical data to the US Coast Guard and other vessels in your vicinity.  Press the “Red” button on the radio and the communications begins.

What is a MMSI?

The Maritime Mobile Service Identity (MMSI) is a unique nine-digit number that identifies transmitted signals within the GMDSS system.  It functions like a telephone number for the devices on your boat.  The MMSI is assigned to a vessel, and the same MMSI is programmed into all shipboard equipment that transmits and receives digital signals, including VHF radio, medium and high frequency radios, AIS (Automatic Identification System), and INMARSAT satellite terminals. Learn more at the US Coast Guard Maritime Telecommunications website.

The US Power Squadron has been authorized by both the Federal Communications Commission (FCC) and the U.S. Coast Guard to assign MMSI numbers only to vessels that meet the following criteria:

  • Used for recreation only
  • Not required by law to carry a radio
  • Not required by law to have a FCC Ship Station license
  • Vessel is under 65' in length
  • Do not communicate with or visit foreign ports (i.e. Canada, Bahamas, Mexico, and the Caribbean)

If you do not meet these criteria, you are legally required to obtain a Ship Station License from the FCC. They will issue an MMSI number with a Ship Station License.

How do I Obtain an MMSI Assignment?

The United States Power Squadron is authorized by the Federal Communications Commission (FCC) and the US Coast Guard (USCG) to issue MMSIs to US flagged vessels not subject to Safety of Life at Sea (SOLAS) Convention requirements.  This includes almost all recreational boats.

USA Go to the US Power Squadron website (MMSI Registration page) and (1) register as a new or returning user, then (2) complete the online form.   It’s that simple and it is free.

Foreign Ports  For vessels traveling to international ports (including Canada and Mexico), the process is different.  You will go to the FCC online services and register your vessels transmitter (VHF/MW/HF radios) using FCC Form 605 (Ship, Aircraft, Amateur, Restricted and Commercial Operator, and General Mobile Radio Services) mounted with your vessel.  The issued license is both an operator and a station license that will be carried onboard your vessel.  The FCC will issue you an eleven-digit MMSI number for your transmitters.

How to Update or Change an MMSI Registration

If your MMSI registration information or contact information changes for any reason, you must update your registration.  If you sell your DSC-equipped radio or AIS or the boat these devices are mounted on, you must cancel your MMSI registration and should inform the new owner of the need to reregister the MMSI.  This is necessary to ensure that the US Coast Guard is able to contact the right persons if a distress situation were ever to occur.  These registration changes can be accomplished by contacting the organization or agency which originally registered your MMSI.

Want to Learn More?

The America’s Boating Club offers an in-depth look at this system in their Marine Communications Systems course.

Want to learn more but not take a course?  Then take the US Power Squadron Using VHF & VHF/DSC Marine Radio seminar.