VATNIEU4500 | Goods sent from Northern Ireland: goods sent on sale or return, approval or similar terms
From HM Revenue & Customs · VAT Northern Ireland and the EU
Where goods are sent to an EU member state on sale or return, approval or similar terms, the movement represents an intra-single market transfer of own goods. This is due to the goods not being removed in the course of a supply to the recipient. A supply will only occur if the recipient subsequently adopts the goods and this will take place in the member state to which the goods have been sent. As a result, the Northern Ireland owner may be required to register in that member state. In the meantime, the movement of the goods represents a transfer of own goods