Most countries offer online registration of Cospas Sarsat 406MHz Beacons. Contact and registration website details can be found here. If the country allows registration in the International Beacon Registration Database (commonly known as the ‘iBird’.) this can be accessed here.
If you need to register by post, the following common registration forms can be downloaded at the links below.
Online registration is available here
The registration form can be downloaded from here
Online registration of EPIRBs, PLBS and MOB devices with MMSI number is decribed here