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VOL. 11 NO. 2
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What is an MMSI?

Why your boat needs a Maritime Mobile Service Identity

Comparing coverage

A Maritime Mobile Service Identity is a nine-digit number that uniquely identifies your boat, you the owner and your contact information. Each Digital Selective Calling radio needs to be registered and assigned an MMSI number. Your DSC radio can be used to send a distress alert to the U.S. Coast Guard and nearby vessels (with DSC radios in receiving range) or to selectively contact another vessel when you know its MMSI number.

There are four types of MMSI numbers, each intended for a certain purpose:

  • An individual vessel (ship station identity)
  • Groups of vessels (group ship station identity)
  • A shore-side facility (coast station identity)
  • A group of shore-side facilities (group coast station identities)

How do you get an MMSI number?
You can get your MMSI number online from

All DSC equipment associated with your boat should use the same MMSI number because it serves to identify the vessel, not the radio. If you sell the boat, the MMSI number is normally transferred with it (after changing the owner information). This information is stored in the Coast Guard Search and Rescue database. You must program your MMSI into your radio (once and only once, according to your radio’s installation manual), so that your MMSI number will be transmitted with every DSC call.

If you're planning to travel outside of the territorial waters of the U.S., you must obtain an MMSI from the FCC. You can read more information at their website.

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