Carrier registration
The Carrier, Broker and Dealer register
The short answer
The public register of everyone allowed to carry, broker or deal in waste. Anyone taking waste off you should be on it, and checking is free.
In practice
Registrations run out. Handing waste to somebody whose registration has lapsed is a duty of care failure by you, not only by them, which is why the expiry date is worth watching rather than the certificate you were shown once.
Where LoadSnap touches it
LoadSnap checks registrations against the Environment Agency register and warns before one lapses.