The ITU portal provides a webpage to find information about vessels, based on their MMSI:
Why do you need an MMSI for AIS?
All AIS equipment has to be programmed with the accurate MMSI (Maritime Mobile Service Identity) which is the unique identifier that Maritime Authorities worldwide award to each vessel that requires it, be it for regulatory requirement or voluntary request.
How to reprogram an AIS transponder and change the MMSI?
Normally reprogramming an AIS transponder require that you contact a certified authorised dealer. Because it is highly sensitive information, it is not a simple task.
If you have a TRUE HEADING CTRX transponder, we can reprogram it for you. Just contact us here, this is a service that we provide.
AIS transponders must be programmed with the MMSI number, among other data. MMSI is the unique identifier for each ship.
This number will be used for all communications equipment such as radio beacon and DSC radio.
For Spanish vessels, the procedure to obtain the MMSI is done through Dirección General de Marina Mercante.
In the case of the class B transponder AIS CTRX by Trueheading, the certification number is 57.0003