The European Union requires the use of its own EU EORI when goods leave the country, and the UK version is necessary for the goods to enter the UK. These numbers have additional customs requirements for shipments, and failure to comply with these will mean the consignment will not pass the borders, officials will halt goods, delay delivery, or possibly they will be denied entry to the UK altogether. Visit: What is an EORI number to get started.
Additional paperwork is also needed to get goods to pass through customs, and these declarations are specific to the interests being shipped. The need to complete this documentation correctly cannot be overstated. It is vital that your goods clear customs, and not doing so will mean delayed shipments, accrual of fees, and a cut into your profit margin. Visit the UK government advisory page for further information.