In some cases, the Union status of goods - while being transported between 2 different areas of the Union (or UK) and crossing the external EU border during transport - needs to be verified in the form of a document. The T2L document is specifically designed to fulfil this role. It provides the receiving customs authorities with certainty that the goods were in free circulation the moment they left the point of departure.
This will occur when the goods are transported by sea or air, and in such situations the port or airport is considered to represent the external EU border.
A T2L document can be issued retrospectively where the cargo has arrived at its destination and no T2L document has been made - necessary to prove the Union status and avoid import duties - the cargo can remain under the supervision of the customs authorities until the T2L document is issued.