You will require this if you intend to operate a 406 MHz distress beacon.
Registration of this type of beacon allows search and rescue organisations to access the registration database and find details of registered vessels, aircraft or vehicles, and details of up to three nominated emergency contacts if a beacon is activated and contact cannot be made.
Analogue Emergency Position Indicating Radio Beacons and Personal Locator Beacons operating on 121.5 MHz are no longer licensed for use and should not be used or offered for sale.