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About MMSI


To obtain an MMSI number -



All vessels operating on the high seas require a Maritime Mobile Service Identity (MMSI) number to participate in the Global Maritime Distress & Safety System (GMDSS). In addition to GMDSS participation the MMSI number also serves as a unique identifier of the vessel for all communications. As the international governing body for telecommunications the International Telecommunications Union (ITU) has set the international conventions for the use of MMSI numbers. MMSI number is a 9-digit code issued by the host country agency for use in VHF marine radio equipment, AIS transponders, EPIRB's, and all INMARSAT satellite terminals. By international agreement, the ITU sets the rules that determine how MMSI's are assigned and used. In the United States the Federal Communications Commission (FCC) and in Canada Industry Canada (IC) are responsible for actually assigning MMSI's to commercial and recreational vessels. (See MMSI and AIS Transponders for more.)

Further detail on the format for US MMSI numbers can be found on the USCG website.


Global Maritime Distress & Safety System (GMDSS) was developed by the United Nations agency, the International Maritime Organization (IMO), as the internationally accepted system of coordinated radio communications (ship-to-ship and ship-to-shore) using satellite and terrestrial networks for commercial vessels.

The GMDSS consists of several systems, some of which are new, but many of which have been in operation for many years. The GMDSS radio carriage requirements depend upon the ship's area of operation, rather than its tonnage. The system also provides redundant means of distress alerting, and emergency sources of power. Recreational vessels are not required to carry GMDSS equipment; however it is strongly encouraged for all vessels on international voyages or traveling greater than 25 nm offshore because of the very efficient communications and rapid distress response. All vessels near shore and on the high seas are strongly encouraged to apply for an MMSI number to allow the use of Digital Selective Calling (DSC) in the case of an emergency.
Automatic Identification System (AIS) has become an important element of the GMDSS monitoring system because of its ability to provide immediate and accurate contact between vessels. To help with the coordination of vessel identity AIS users use the same MMSI numbers assigned to the vessel for GMDSS purposes. The system is backwards compatible with DSC, allowing shore-based GMDSS systems to affordably identify and track AIS-equipped vessels, and is intended to eventually replace the existing DSC-based transponder systems.


Each MMSI number provides a unique vessel identifier for marine monitoring and identification systems to facilitate communications, emergency response, customs and border security, and even commercial call tracking and billing. Unlike shore based phone systems the MMSI number is not synonymous with a "phone number" because it is attached to a vessel and not an individual. Vessels equipped with DSC can make direct bridge-to-bridge calls using MMSI "Vessel-to-Vessel" features. Further, vessels equipped with AIS equipment can rapidly identify and be identified via this unique number on any radar, chart plotter or ECDIS (electronic chart display information system) display. All equipment on a specific vessel must display that vessel's one identifying number. In some fleet circumstances vessels can share an MMSI number but this is only when done when the vessels operate in conjunction with one another such as tug and tow. AIS facilitates monitoring of one vessel by another, or by a properly equipped shore station agency, such as the Coast Guard, to pinpoint the exact location of a vessel in distress.

In the U.S., the FCC and Coast Guard maintain a database of MMSI's that contains details on each vessel, its owner, and homeport. The information should be updated bi-annually. Commercial vessels are entered in this database when they apply for a radio station license, or apply for an amendment. Domestic users (non-commercial) who do not travel outside of the US waters can be issued an MMSI number without applying for a Ship Station License.



Prior to delivery to the customer (end-user) each AIS Class B transponder is programmed with the unique MMSI number assigned to the vessel to be carrying such equipment. The MMSI number assigned to each device must be accurately programmed and updated as necessary. The vessel MMSI number automatically transmits once every 30 seconds along with a basic position report. The position information can be seen by anyone with AIS receive equipment. This will most often be the VTS, Commercial vessel operators, or the Coast Guard.

Commercial vessel operators and others using licensed radio equipment will obtain their MMSI numbers directly from the FCC for a fee of $120 US (subject to change). US Recreational users who remain in US waters and only carry VHF, EPIRB and Radar are not required to be licensed. However, they may wish to obtain an MMSI for use with a VHF DSC radio, EPIRB or Class B AIS Transponder (regulations are still under review, and therefore subject to change).

MMSI numbers can be obtained at

Frequently Asked Questions about MMSI numbers for AIS:

1. What vessels are required to obtain an MMSI number?

Answer: Only those vessels on international voyages or US flag commercial vessels greater than 65 feet that are not carrying passengers or engaged in fishing are currently required to carry AIS. The specific carriage requirements for US vessels are specified in title 33 CFR 164.46. Each country has slightly different carriage requirements, consult your individual Coast Guard carriage requirements prior to making an AIS purchase.

2. Do Yacht tenders require a separate MMSI number?

Answer: No, the yacht's tender or life raft should carry the same MMSI number as the parent vessel unless the craft is not normally fitted aboard or in davits.

3. What do the 9 digits MMSI numbers each mean?

Answer: Each of the groups of digits within the number has unique meanings that vary slightly by country. Further detail on the format for US MMSI numbers can be found on the USCG website.