If Brexit happens without a deal on the 29th March 2019 then Britain will lose the current rights it has for Importing and Exporting with the European Union.
To be able to continue to import/export to and from the EU if this should happen businesses will need to register for a EORI Number (Economic Operator and Registration Identification). HM Revenue and Customs (HMRC) will use this number to identify you and collect duty on any goods as required.
To ensure you are not left in a position where you are unable to trade because of the need to import/export we would suggest you obtain an EORI number in advance of this date.
For details of how to obtain an EORI number please see the link below: