On 29 March 2017 the UK formally notified to the European Council its intention to leave the EU.
"There is no reason to pretend that this is a happy day, neither in Brussels, nor in London", said Donald Tusk, President of the European Council on the day. He added that the community of 27 would remain "determined and united" in the negotiations ahead: "Our goal is clear: to minimise the costs for the EU citizens, businesses and member states."
The Article 50 notification follows the results of the UK referendum on 23 June 2016.
For the latest developments please check : https://ec.europa.eu/info/european-union-and-united-kingdom-forging-new-partnership_en