Cancellation is the physical ‘use’ of a GO certificate and the method of allocating the attributes of that electricity to a single end-user.  Cancelling a GO is the only way to remove a GO from the market and redeem its benefits. Cancelling ensures that the certificate will not be traded, given, sold, or used by another end-user.  End-consumers will most often purchase GOs with the intent of eventually cancelling it as opposed to selling it again for another end-user to cancel.