U.S. flag

An official website of the United States government

Dot gov

Official websites use .gov
A .gov website belongs to an official government organization in the United States.


Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

About MMSIs

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 for use in the following equipment:

  • Radios with Digital Selective Calling (DSC) capability
  • AIS (Automatic Identification System) transceivers of all types
  • Satellite Earth Stations, terminal types B/C/M

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).

Correcting an MMSI

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 and 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.

MMSI Categories

Coast Station ID for Public Coast (FC), Private Coast (FCL, FCL2), Alaska Public Fixed (APC), and Alaska Private Fixed (APX, APX2)

All Coast Station ID numbers supplied by the Commission will be in constructed in the following format in accordance with ITU regulations:


Here, the first two digits will be zeroes, the next 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 6 to 9 will be any digit from 0 to 9.

International Handheld VHF MMSI for Marine Utility (FCU1) or other Mobile-based Marine Licensing

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.

Obtaining an MMSI

If your Coast Station (fixed or mobile) requires a license, you may 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 an attachment to your application. In this attachment, ensure that the type of MMSI requested is specified. Please be aware that an MMSI will not be issued without the presence of an attachment on the application.

Fixed Coast stations will use the 0102M3I4D5X6X7X8X9 format, consistent with ITU Regulations. Licenses that are based upon a mobile marine framework, and utilizing a DSC-Capable VHF Radio may request a 81M2I3D4X5X6X7X8X9 format in order to ensure greater accuracy and safety in marine emergencies.

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.

Friday, September 15, 2023