A Letter of Authorisation (LoA) is a communication from the host country of a carbon project stating that a carbon credit from that project can be transferred abroad under the Paris Agreement's Article 6 mechanism.
Under Article 6, LoAs are provided to confirm that a carbon credit, or mitigation unit, can be transferred abroad, and that the host country will remove this unit from its national carbon accounting and NDC. It represents a commitment to apply a corresponding adjustment to an NDC once the transfer takes place.