About MSSIs

Maritime Mobile Service Identities (MMSIs) are nine-digit numbers used by maritime digital selective calling (DSC), automatic identification systems (AIS) and certain other equipment to uniquely identify a ship or a coast radio station. MMSIs are regulated and managed internationally by the International Telecommunications Union in Geneva, Switzerland, just as radio call signs are regulated.

If you have a marine radio with DSC capability, you must obtain a nine-digit maritime mobile service identity number, and have it programmed into the unit before you transmit. Each vessel requires only one MMSI number.

An MMSI is vital data point for both domestic and international emergency personnel. Maintaining updated and accurate data in your license record is critical to ensuring maritime safety. To update a license record, please file an application in ULS to maintain the accuracy of your vessel’s information.

MMSI Numbers are:

  • Required to be programmed into radios with Digital Selective Calling (DSC) capability
  • Entered into AIS (Automatic Identification System) transceiver
  • Should be used for all INMARSAT B/C/M terminals

The system is comprised of a series of nine (9) digits which are transmitted over the radio path to uniquely identify ship stations, ship earth stations, coast stations, coast earth stations and groups of stations. The first three digits of an MMSI indicate the issuing country.

MMSI numbers may only be used for one vessel and may not be re-used, unless in the special case of a vessel transfer (please see the Vessel Transfer Tab).

MMSI Categories

International Vessel MMSI

All Vessel-formatted MMSI numbers supplied by the Commission will be in constructed in the following format in accordance with ITU regulations:


Here, the first three digits are representative of the maritime identification digits (MID) which are indicative of the home country of the licensed vessel. The following digits from 4 to 9 will be any digit from 0 to 9. The Commission only issues MMSI numbers ending in 0 (zero). Should your MMSI number not end in this digit, and you wish to travel internationally, please acquire a suitable MMSI from the Commission, as numbers that do not meet this requirement are not accepted into the ITU database.

International Handheld VHF MMSI

All Handheld VHF-formatted MMSI numbers supplied by the Commission will be in constructed in the following format in accordance with ITU regulations:


Here a distinctive 8 precedes digits 2, 3, and 4 (MID) and the trailing Xs may be any figure from 0 to 9. This unique MMSI format for handheld VHF radios assist maritime emergency personnel in making better informed decisions based on the more limited coverage area and battery life of these radios versus hard-mounted VHF vessel radios.

Domestic Vessel MMSI

For vessels that do not make international voyages or communicate with foreign ports, a domestic vessel MMSI number may be obtained and used. Similarly formatted to international MMSIs, these follow the M1I2D3X4X5X6X7X8X9 format as well. These MMSIs may not be used internationally and will end in a digit other than zero. They may be obtained from the Commission's MOU partners listed in the "Obtaining an MMSI" tab.

Obtaining an MSSI

If your vessel requires licensing by the FCC, you will obtain an MMSI number during the application/licensing process when you file online with the FCC.  In order to obtain a new MMSI number, please indicate that you wish to be assigned a new number in Question 11 of FCC Form 605, Schedule B.

In the special case that you wish to be assigned a new MMSI for your DSC-Capable VHF Handheld Marine Radio, please select P for Portable on Question 4, type of license on FCC Form 605, Schedule B. Please ensure that you add an attachment specifically requesting assignment of a VHF Handheld Formatted MMSI, otherwise the system will automatically assign a standard Vessel Format MMSI to your license.

After the FCC grants a new, modified, or administratively updated ship station license, it reports the MMSI and certain other data to the International Telecommunication Union’s (ITU) Maritime mobile Access and Retrieval System (MARS) as well as the US Coast Guard’s Port State Information Exchange (PSIX) so that both domestic and international  search and rescue authorities also have access to the information.  Licensees may check the MARS or PSIX databases to confirm that their information is listed and up to date.

Domestic MMSI numbers

Information is contained in the Public Notice (DA 12-1989) announcing agreements with and the procedures for private entities to apply to issue MMSIs. If an FCC ship station license is not required, domestic MMSI numbers can be obtained from one of the official Private Registrant entities:


United States Power Squadrons, Inc

Shine Micro

Domestic MMSI numbers are not usable internationally. MMSI numbers issued by other authorized entities are valid only for ship stations that do not have FCC-issued licenses. Since the ULS will not accept the MMSI that was issued by another entity, you should leave the field blank and the FCC will issue you a new MMSI number.

Vessel Transfer

In the case of the sale or transfer of a vessel, the MMSI programmed into the vessel’s onboard radio(s) may be reused by the new vessel’s owner. In this case, please follow the procedure below:

In order to re-use the same MMSI number:

  1. A request must be made directly to the Commission by the previous owner to cancel the license.
  2. Following cancellation of the previous license, the MMSI can be entered into a new station application.

Should you need to correct an MMSI on your license record after a new license has been granted submit a request via e-support.  To assist us in processing the request please be certain the request description field includes:

  • Licensee name
  • Vessel Call sign
  • Name of Vessel
  • Official Ship Number (Coast Guard Documentation No. or State Registration No.)
  • Correct MMSI Number

Should you need to correct the MMSI number already programmed into your DSC-capable VHF marine radio, please follow the radio manufacturer’s guidelines in order to reset your MMSI input.

Tuesday, October 4, 2022