05/01/2026
ARE YOU IGNORING THE BEST SAFETY FEATURE ABOARD YOUR BOAT?
Boater's Guide: Everything You Need to Know About MMSI Numbers
May is boating safety month, so we are diving into a crucial topic for your on-the-water safety and communication: the Maritime Mobile Service Identity (MMSI) number. Whether you just bought a new boat or are upgrading your vessel's electronics, here is everything you need to know about what an MMSI is, why you want one, and how to get it.
What is MMSI and How Does It Work?
A Maritime Mobile Service Identity (MMSI) is a globally unique, nine-digit number that identifies your specific vessel. You can think of it as a "telephone number" for your boat. The number is coded with information indicating the issuing government, the type of station, and your vessel's unique identity. To use an MMSI, you must program the number into your VHF radio equipped with Digital Selective Calling (DSC).
What Are the Benefits of Setting Up MMSI?
Programming an MMSI into your electronics dramatically enhances your safety and communication capabilities:
Automated Distress Calling: The most significant benefit is the ability to transmit an automated distress call. In an emergency, pushing a single distress button on your DSC radio transmits a signal containing your exact MMSI number to the U.S. Coast Guard and all other DSC-capable receivers within range.
Faster, Smarter Rescues: When the Coast Guard receives your alert, they use your unique MMSI to pull up your pre-registered vessel details and emergency contact information, allowing them to mount a highly efficient rescue effort. Furthermore, if your radio is linked to a GPS receiver, your exact latitude and longitude will be broadcast alongside your MMSI.
AIS Visibility: If you want to use an AIS transponder to broadcast your course, speed, position, and vessel name to other ships in your area to avoid collisions, an MMSI number is absolutely required.
How to Get an MMSI Number
How you obtain an MMSI depends entirely on how and where you plan to use your boat.
For Recreational Boaters in U.S. Waters: If your boat is under 65 feet, is used strictly for recreation, and will never visit a foreign port or communicate with foreign stations, you are not legally required to carry a radio. Therefore, you can get a free or low-cost MMSI through approved U.S. organizations such as BoatUS or the U.S. Power Squadrons. These organizations will relay your registration information directly to the U.S. Coast Guard.
For Boaters Traveling Internationally: If you plan to sail to a foreign country (such as Canada, Mexico, or the Bahamas) or communicate with foreign stations, you must get an FCC Ship Station License. The Federal Communications Commission (FCC) will issue an internationally recognized MMSI as part of this ten-year license. You will also need a Restricted Radiotelephone Operator Permit (RROP) for yourself. Note: If you already have a domestic MMSI from BoatUS and plan to leave the country, you will have to delete your existing MMSI and replace it with an FCC-issued one.
For Handheld Radios: If you have a portable handheld VHF radio with DSC, the FCC has a special MMSI class for handhelds. This allows the handheld radio to be licensed independently and moved between different vessels.
A Final Rule of Thumb: Remember that an MMSI belongs to the vessel, not the user. If you ever sell your boat or your radio, you cannot simply remove the MMSI from memory. You must update or transfer the registration so the new owner's emergency contact information is tied to the vessel.
