23 November 2020 
Andrea Marshall, Tax Specialist
This is an interesting change. HMRC have issued VAT and overseas goods sold directly to customers in Great Britain from 1 January 2021. The guide opens with this (Andrea has added the bold emphasis):
From 11pm on 31 December 2020, UK supply VAT is due at the point of sale on consignments of goods that are outside Great Britain (England, Scotland and Wales) and sold directly to customers (not through an online marketplace) in Great Britain with a value of £135 or less.
This snippet suggests that to use "UK supply VAT" you should be providing your UK VAT reg number to EU and non-EU suppliers:
The seller will not need to charge and account for VAT if the customer gives them their VAT registration number, and they confirm it’s correct using the new online service that will be available from December 2020.
The seller can add a note to the invoice (for example, by writing ‘reverse charge: customer to account for VAT to HMRC’) then send it to the UK business customer.
The business customer will then be responsible for accounting for any VAT due on their VAT Return using a ‘reverse charge’ procedure, and will be able to recover the VAT as input tax on the same VAT Return under normal VAT recovery rules.
Sellers do not have to register for VAT if they only sell goods that are outside the UK at the point of sale to UK VAT-registered businesses.
It appears that this applies, even if the sale if via an online marketplace, provided that the goods are outside GB at the point of sale. See VAT and overseas goods sold to customers in Great Britain using online marketplaces from 1 January 2021
The online marketplace will not need to charge and account for VAT if the customer gives them their VAT registration number, and they confirm it’s correct using the new online service that will be available from December 2020.
The online marketplace can add a note to the invoice (for example, by writing ‘reverse charge: customer to account for VAT to HMRC’) then send it to the UK business customer.
The business customer will then be responsible for accounting for any VAT due on their VAT Return using a ‘reverse charge’ procedure, and will be able to recover the VAT as input tax on the same VAT Return under normal VAT recovery rules.
