Article 50, the official signal that Britain will leave the EU, will be invoked by the end of March 2017, Prime Minister Theresa May has revealed.
It will trigger the start of negotiations with Europe on matters such as trade and free movement of people and will give the country two years to agree terms of leaving the union.
That means it would be wrapped up by March 2019, before European Parliamentary elections expected later in that year.
Negotiating with Europe can not begin until Article 50 of the Lisbon Treaty is invoked and the confirmation of a timetable will be welcome news to business as it will provide more certainty.
However, former business minister Anna Soubry raised concerns over starting the process so soon, saying: "We need to know our red lines going into this process".
"Triggering Brexit as early as March really concerns me. It troubles me hugely, because we won't have had the French elections, we won't have had the German elections and it is going to take a lot of time and effort to disentangle ourselves and get the right deal," she said, speaking on ITV's Peston on Sunday show.
British Chambers of Commerce director general Adam Marshall said: "For most businesses, getting Brexit right is far more important than doing it quickly. Now that the Prime Minister has set a timetable, the government must demonstrate to business that it has a clear and coherent strategy to defend the UK's economic and business interests in the negotiations that lie ahead."
Setting a date for starting withdrawal comes after it was confirmed that a new bill will be introduced in Parliament next year to repeal EU laws.
May is expected to say more on the matter at the Conservative party conference in her first speech as leader.
European Council President Donald Tusk welcomed the decision, saying it would bring clarity on the start of talks.
"Once Article 50's triggered, EU27 will engage to safeguard its interests," he tweeted.
PM May's declaration brings welcome clarity on start of Brexit talks. Once Art. 50's triggered, EU27 will engage to safeguard its interests— Donald Tusk (@eucopresident) October 2, 2016