The new rules are valid from 1st July 2021, and they refer to the abolition of VAT exemptions for small value shipments. Specifically, it refers to goods worth €22 or less and a new special scheme for the distance selling of goods, where the goods are estimated at €150 or less if you do business in the UK and deliver goods to EU consumers. In that case, if the actual value of the goods is less than €150, you will be covered by the new Import One Stop Shop (IOSS). Incoming goods will have separate regulations If the value does not exceed €150.
Electronic interfaces for online sales, such as Amazon or Shopify, will become VAT payers, not your online store itself. Your online store will bear a direct VAT tax on the goods you deliver to the consumer in any EU member state. However, this VAT can be declared through the OSS declaration (One-Stop-Shop declaration) in one EU Member State from 1 July 2021 and will avoid the need for registration in each Member State.
More details can be found on the HMRC webpage.