Maritime Mobile Service Identity (MMSI) numbers are a series of nine digits used to uniquely identify a DSC radio or a group of DSC radios on a vessel. It is important to note that you don’t need to get an MMSI number if your handheld radio doesn’t have DSC.
The MMSI has a standard format (just like a telephone number), and it identifies the type of station, country of registration and vessel identity. In the UK MMSIs are assigned as a part of the ship's radio licensing procedure.
You can get an MMSI number by applying for a ship station license through the Federal Communications Commission (FCC). However, you may still want an MMSI even if you aren’t legally required to have an FCC license, since an MMSI allows you to make emergency calls from your boat.
In the UK MMSIs are assigned as a part of the ship's radio licensing procedure.
When sending a DSC message, the MMSI is automatically included, and you can address messages to specific vessels or groups using their MMSIs.
If you have a marine VHF radio installed on your boat, you will need a ship's radio licence from the OFCOM website. This is free of charge online, or you can do this via post, but there is a charge. You can obtain an application form for a ship's radio by applying via: ofcom.org.uk
If you have more than one DSC Radio on your vessel, they should each have the same MMSI number. However in the UK, any handheld DSC radio should be separately licensed and have its own MMSI number.
Identify an approved boat owners' organization that assigns MMSI numbers. The FCC and US Coast Guard authorize organizations to assign domestic MMSI numbers. The application process is relatively simple and you’ll receive an MMSI number immediately. As of 2019, authorized organizations include:
Boat US: https://www.boatus.com/MMSI/MMSI/Home
US Power Squadron: http://www.usps.org/php/mmsi_new