HMRC has published advice on how online marketplaces and direct sellers will deal with VAT for goods from overseas that are sold to customers in Great Britain from 1 January 2021. You can find the guidance below:
Online marketplace guidance: https://www.gov.uk/guidance/vat-and-overseas-goods-sold-to-customers-in-great-britain-using-online-marketplaces-from-1-january-2021
Direct seller guidance: https://www.gov.uk/guidance/vat-and-overseas-goods-sold-directly-to-customers-in-great-britain-from-1-january-2021