UK Prime Minister Theresa May has signed the letter that will formally begin the UK's departure from the European Union.
Giving official notice under Article 50 of the Lisbon Treaty, it will be delivered to European Council president Donald Tusk later on Wednesday, the (BBC) reported.
The prime minister, who will chair a cabinet meeting, will then make a statement to MPs confirming the countdown to the UK's departure from the EU is under way.
In a statement in the Commons, the prime minister will then tell MPs this marks "the moment for the country to come together". May was forced to consult Parliament before invoking Article 50 after it lost a legal challenge in the Supreme Court, but it secured the backing of most MPs earlier this month. 
Article 50 of the Treaty of Lisbon gives any EU member the right to quit unilaterally and shall not participate in the discussions of the European Council. In addition, any agreement to withdraw from the Union would need to be adopted by a qualified majority of 72% of the remaining 27 Member States, representing 65% of the population. The final agreement would also need to be approved by the European Parliament. 

Source: QNA