Brexit is a reality, and the United Kingdom (UK) is officially a non-EU country for VAT and customs purposes. Goods that are sent from the European Union (EU) to Great Britain (GB) and vice versa are now subject to customs, export and import formalities. Luckily, a Brexit deal was reached at the last moment. One of the effects of the deal is that customs duties on goods originating from GB or the EU are reduced to 0%. The rules of origin are therefore very important if you are trading with GB or the EU!
Source Baker Tilly
