I have posted already with the UK Technical Notices for Brexit Preparedness. HMRC has three of these Technical Notices. Further instruction is now issued from HMRC in the form of a Partnership Pack. This is here.
For goods exports, the following is required :
(1) register for an EORI number – not open yet [EORI – is UK Economic Operator Registration and Identification Number] and ensure the EU bloc customer also has an EORI number
(2) check is a special licence is required
(3) get the commodity code from published codes
(4) get the correct Customs Procedure Code (CPC)
(5) decide how to declare to HMRC – this is complex – decide if to pay a Freight Forwarder, an Express Courier, or a Customs Agent/Broker
(6) register for the National Export System (NES)
(7) attach the invoice (and licence if needed) with the goods transport
(8) present the goods to customs
(9) finalise the Export entry on HMRC CHIEF system
(10) keep records for 6 years
The Pack is the first of a series of more specific HMRC instructions. This Pack also covers Goods Imports. It does not cover direct sales on a digital platform.