The UK officially left the European Union on 31 January 2020 at 11:00 pm UK time (23:00 GMT).

Key dates in one glance

  • 23 June 2016 – UK votes to leave the EU in the Brexit referendum (52% leave, 48% remain).
  • 29 March 2017 – UK government triggers Article 50, formally starting the withdrawal process.
  • 31 January 2020 – UK legally leaves the EU at 23:00 GMT, after several deadline extensions.
  • 31 December 2020 – End of the transition period, when most practical changes to rules and trade took effect.

In simple terms: the UK legally left the EU on 31 January 2020, and the practical separation (in trade and many rules) fully kicked in after 31 December 2020.

TL;DR:
The UK left the EU on 31 January 2020 at 11 pm UK time, after a 2016 referendum and a transition period that ran until the end of 2020.

Information gathered from public forums or data available on the internet and portrayed here.