MMSI, the Maritime Mobile Service Identity, at BoatUS, has expanded our Frequently Asked Questions (FAQs) to answer your questions regarding online difficulties, VHF radio questions and general questions about MMSI and how it pertains to your boat.

Questions are grouped by category, so please click on the appropriate question to view the answer. For additional information please contact us at

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MMSI As It Pertains To The Boat

Is the MMSI unique to the boat owner or does it stay with the boat and radio?

The MMSI stays with the radio which it is programmed into. 

  • If you sell the boat but keep the radio, you can update with the new boat information in the Edit Registration Screen.
  • If you sell the boat with the radio, you must cancel your MMSI registration to avoid having the distress linked to you and your personal information should the new owner fail to reprogram the radio or request that the MMSI be transferred over to them.
  • If you kept the boat but have traded or replaced the radio which was programmed, you must cancel your MMSI registration for the same reason stated above.
  • If you obtained a second radio to go on board the same boat, you may program the same MMSI number into that radio.

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I have two boats, in different states and each has a DSC capable VHF radio. Can I get two MMSI numbers?

Yes, in fact YOU MUST if you wish the system to work. In a distress situation, it is vital to identify the particular vessel, home port, etc.

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I have sold my boat & radio. What should I do?

If you sell or trade your boat and radio with an MMSI number programmed into it, please be sure to login and CANCEL the MMSI account to make the number available to the new buyer.  Once it is canceled we will know it is ok to reassign the number to the new owner should they enquire about it.  Do not continue to use the same MMSI number with a new boat & radio as it would still be tied to the one you have sold. Instead, you would need to register for a new MMSI number for any new radio. 

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I have purchased a boat & radio with an MMSI number programmed into it. Can the MMSI number be transferred over to me?

If the MMSI number was assigned by BoatUS and the previous owner has closed the account, we can re-register the MMSI number for 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, Call 1-800-563-1536 and make sure to provide the MMSI number in all correspondence!

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I have purchased a previously owned boat with a DSC radio and I am not sure if it has an MMSI number assigned to it.

Check your owner’s manual for the procedure for obtaining this information from the radio. Tip:  If the DSC features are working, then there is a number programmed into it.  If you cannot obtain the number from the radio, contact the manufacturer for assistance.  

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I have an FCC Ship Station License which has expired and it included an MMSI number. Do I need to get a new MMSI number?

You may re-register your number on the BoatUS website by going to (click on the 3rd option to the left – “Already have a NonBoatUS MMSI”).  Input your current MMSI number and proceed with the application process. Upon completion of the registration the system will assign you your FCC MMSI number rather than one from our database.

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I bought a boat with a Ship's Station License and MMSI. Can I continue to use the call sign and MMSI that came with it?

No, that information applies to someone else. You may contact the FCC to determine whether the previous owner has cancelled the ship station license.  If yes, you can request that the MMSI be transferred over to your own ship station license for that vessel. To contact the FCC, call (877) 480-3201 and select option 2 to speak with a licensing representative. 

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I have purchased a boat with a VHF DSC radio. How can I tell if it already has an MMSI number programmed?

See owner's manual for instructions on how to retrienve number from memory, or try the USCG national group MMSI, 003669999, 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.

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