Goods moving between the UK and EU 27 member states will become liable to import VAT payments after 31 December 2020 when the UK leaves the EU VAT regime as part of Brexit. But, with careful planning EU or UK traders can avoid the cash payments required and keep goods flowing. This can be down through countries’ postponed accounting or deferred VAT regimes.
Source Avalara
See also Importation into Europe: Which countries (will) have a reverse charge or deferral mechanism?
