Below highlights the requirements for EU originating exporters:
It is an absolute requirement of the FTA that any EU originating export to the UK in which the value of the shipment
exceeds EUR6,000.00 requires the EU exporter to be registered in the REX system & quote their REX number
on the sales invoice.
It appears many EU companies have no knowledge of the REX system or how to apply for registration so here is
the link for information & a further link to take them to the Customs authorities authorisation offices
in their own country.
REX Information
REX Registration