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 radio using MMSI, your emergency situation is immediately transmitted with critical data to the US Coast Guard and other vessels in your vicinity.  Press the “Red” button and the communications begins.

What is a MMSI?

The Maritime Mobile Service Identity 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.

How do I Obtain an MMSI Assignment?

In the United States, the National Telecommunications Administration (NTIA) provides MMSIs to federal users, and the Federal Communication Commission (FCC) provides MMSIs to everyone else.  NTIA is as Executive Branch agency under the Department of Commerce, and the FCC is an independent agency.

The United States Power Squadron is authorized by the Federal Communications Commission and the US Coast Guard to issue MMSIs to US flagged vessels not subject to Safety of Life at Sea (SOLAS) Convention requirements.  This includes almost all recreational boats.  Simply go to the US Power Squadron website at, register as a user, then complete the form.   It’s that simple and it is free.

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 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.