Maritime Mobile Service Identity (MMSI) is a unique 9 digit number that is assigned to an individual vessel. It is entered into DSC (Digital Selective Calling) radios and AIS (Automatic Identification System) units used on that vessel. Similar to a cell phone number, your MMSI number is your unique calling number for DSC radios or an AIS unit. The information provided when obtaining an MMSI number is transferred into the U.S. Coast Guard's national distress database for use in emergency situations.

There is a $25 fee to register for MMSI through this program; however, the registration fee will be waived for current BoatUS Members.

Digital Selective Calling (DSC) is a radio technology allowing enhanced distress radio messages to be sent digitally. Since 1999, the FCC (Federal Communications Commission) has required new fixed mount VHF radio sold in the U.S. to be equipped with the DSC feature.

DSC radios have a one-button emergency transmit button that sends the vessel's unique MMSI number. In addition, if the DSC equipped radio is linked to a GPS or Loran unit, the distress call will include the vessel's position. Should the operator become incapacitated, the radio will continue sending the mayday. In addition, a DSC equipped vessel with an MMSI number can make a "private" hailing call to another DSC-equipped vessel. Only the vessel being called will receive the initial contact, but the subsequent conversation will take place on an open, “working” channel, which can be monitored by any VHF equipped vessel within your broadcast range.

Please refer to you radio’s owner’s manual or contact the radio manufacturer for additional information about you radio’s capabilities.

BoatUS MMSI numbers are for US registered or documented, recreational vessels under 65’ that are not visiting or communicating with foreign ports. The registration data provided to BoatUS is only transferred into the U.S. Coast Guard Search & Rescue Database (MISLE). International search & rescue agencies do not have access to the registration data provided to BoatUS.

Registration data for FCC-assigned MMSI numbers go into the International Telecom Union (ITU) database that is accessible to international search & rescue agencies. In order to be accepted into the ITU database, any FCC assigned MMSI must end in zero. This is why the BoatUS MMSI number cannot be re-used when later applying for an FCC MMSI number for international cruising.

Yes. If you have multiple radios that are only used on one boat, you should input the same MMSI number in all radios.

If you plan to use the handheld on multiple boats, you might want a separate MMSI number so that you can update the registration information according to which boat it is currently on. If you only plan to use the handheld on one boat, you can use the same MMSI number that is programmed into the fixed mount radio onboard.

No, recreational boats under 65' that do not communicate with or visit foreign ports do not require a VHF license.

Check the owner's manual for instructions on how to display the MMSI number programmed into the radio or place a direct or “private” hail to another MMSI known to you and ask that the originating MMSI (your MMSI) be read back to you from the receiving unit's display screen.

If you need to test to see if the DSC feature is working, do not test the red distress button as this will send out an illegal false alarm and cause an unnecessary rescue response! Instead, you may run a test call to the nationwide Coast Guard MMSI number, 003669999. Enter this number into your radio’s calling memory and select the “Test Call” option from the radio’s list of individual DSC calls, then press the “call” or “enter” key. Your radio will silently hail the Coast Guard with a digital signal on channel 70. If everything is working properly, your radio will almost immediately receive the Coast Guard’s acknowledgement of your call, providing assurance that both your radio and the Rescue21 system are operating properly. Alternatively you may also use the DSC function to privately hail another boater’s MMSI number so that they can verify what MMSI came up on their ID. The DSC functions do not work until an MMSI number is programmed in. If your radio contains or is connected to a GPS, the signal will also provide your exact coordinates.

No. You are required to obtain a Ship’s Station License from the FCC and they will provide an MMSI number that is valid for international cruising. To obtain a Ship’s Station License from the FCC, please visit or call 877-480-3201

No. BoatUS MMSI numbers are only for U.S. registered or documented vessels. You must obtain an MMSI number from the country the vessel is flagged in.

No, you will need to obtain a new MMSI number from the FCC and reprogram your radio(s) with the MMSI number the FCC issues. The new MMSI will be coded for international travel and the registration will be entered into the international search & rescue database. To obtain a Ship’s Station License from the FCC, please visit or call 877-480-3201

No. Registration for EPIRB (Emergency Position-Indicating Radio Beacon) is done through NOAA ( NOAA oversees this satellite search and rescue system which is not related to DSC VHF marine radios however you should provide your EPIRB ID code in the provided field when obtaining a MMSI number.

Channel 70 is to be used exclusively for DSC and DSC capable radios automatically monitor CH70 as well as whatever channel you are otherwise using or monitoring.. As a recreational boater, you do not need to monitor it.

It is in effect "private hailing" of another vessel whose MMSI number is known to you. Once contact is established between the vessels, they are automatically switched to the preselected "working channel", and the "privacy" ends at that point, meaning that the transmission (conversation) can be heard by any other vessel monitoring that channel.

Your login name and password are case sensitive and must be inputted exactly as registered. If you are uncertain of your login name and password, please visit and click on “Forgot your password?” and your login name & password will be sent to the email address you registered with.

The action you need to take depends on who has ownership of the radio(s) that were programmed with the MMSI number you obtained:

  • If you kept all the radios that had the MMSI number programmed into it, you can update your registration with the new boat information when you buy a new boat.
  • If all the radios that are programmed with the MMSI number have been given to the new owner, you must transfer the MMSI number to the new owner by logging into your MMSI account and selecting the “Transfer to New Owner” button. This cancels your MMSI registration and avoids having any future distress calls from the MMSInumber linked to you and your personal information. The new owner will then receive an email with instructions on how to claim the MMSI number
  • If you retained one or more of the radios with the MMSI number and the new owner also has one or more radios with the MMSI number programmed into it, you need to work with the new owner to determine who is going to be responsible for obtaining a new MMSI number and having the radio(s) reprogrammed. It is critically important that two individuals are not using the same MMSI number on different boats

If the MMSI number was assigned by BoatUS and the previous owner has cancelled their registration, BoatUS can transfer the MMSI number to the new owner. If the previous owner has not closed the account, we will attempt to contact them to verify that they are not still using the number in another radio. If the previous owner cannot be contacted or is still improperly using the MMSI you will need to reprogram the radio with a new number. To check if your MMSI was assigned through BoatUS, email

No. You can register your FCC issued MMSI number on the BoatUS website by going to Note that if you plan to make broadcasts in foreign waters you will need to obtain a new FCC licenses.

Ship Station Licenses are not transferrable from one boat to another, but the FCC will offer a prorated refund for the years remaining on the ship station license should the owner cancel once the boat has been sold. BoatUS cannot assist with the MMSI transfer process for an FCC assigned MMSI in connection with a ship station license, but if the prior owner of the MMSI has cancelled the ship station license through the FCC, the MMSI can be transferred to the ship station license of the new owner of the vessel and programmed radio by contacting the FCC at 1-877-480-3201. If the new owner is not required to carry a Ship Station License and has confirmed that the previous owner has cancelled his ship station license, the new owner can input the FCC assigned MMSI into the BoatUS database by going to

Class A and Class B AIS units transmit your position and any identifying information you have programmed into the AIS unit, including your MMSI number. An FCC-issued MMSI number and corresponding vessel and owner information is publically accessible. Vessel tracking websites such as & track vessel movements using AIS transmissions and identify vessels from their MMSIs using the FCC database. Information provided to BoatUS during the registration process is not provided to any vessel tracking websites or non-government organization.