Prime Minister Theresa May is to officially notify the European Union next Wednesday that the UK is leaving, the BBC reports.
Downing Street said she would write a letter to the EU’s 27 other members, adding that it expected negotiations to then begin as quickly as possible.
The move comes nine months after people voted 51.9% to 48.1% in a referendum.
Talks on the terms of the departure and future relations are not allowed under the Article 50 process until the UK formally tells the EU it is leaving.
If all goes according to the two year negotiations set out in the official timetable, Brexit should happen in March 2019.