The UK officially left the EU on January 31, 2020 and from January 1, 2021, it will cease to apply European standards. i.e. mid-November is considered the limit beyond which a possible trade agreement could not enter into force at the end of the transition period.
From January 1, 2021, it will no longer be possible to ship goods via the EMCS system, nor to issue a SAD within the framework of European regulations to cover shipment to the European Union.
Brexit : Since 31 January 2020, United Kingdom is no longer Member of the European Union. Transition period is still on 31 decembre 2020.