The UK's representative to the European Union, Sir Tim Barrow, notified the block's council president, Donald Tusk, of the date in a letter this morning.
The currency movements come in the wake of confirmation from Downing Street that Article 50 will be triggered next Wednesday, 29 March, after the Brexit bill was made law last week when the Queen granted royal assent for the Brexit bill.
The prime minister has long said she would start the Article 50 process by the end of this month.
Brexit minister David Davis has said there would be no sudden drop in numbers, as it would take years to fill low-skilled jobs in hospitality, social care and agriculture now done by immigrants.
"Everything is ready on this side", commission spokesman Margaritis Schinas said. The top politicians will carve out negotiating positions and guidelines for the European Commission, the bloc's executive arm, to follow.
Notification comes 279 days after the referendum of June 23 previous year delivered a 52%-48% majority in favour of withdrawal.
"We are confident we can deliver the necessary reforms within the legislative timetable, and have also been clear that we envisage a phased process of implementation".
Mr Farron repeated his call for voters to have the final say on the deal negotiated by Mrs May, arguing that departure from the European Single Market was not on the ballot paper in June.
Davis said ministers would seek a Brexit deal "that works for every nation and region of the United Kingdom and indeed for all of Europe - a new, positive partnership between the United Kingdom and our friends and allies in the European Union".
"We want negotiations to start promptly", said the Prime Minister's offcial spokesman this morning.
"I have set out my objectives", she said.
He added that Number 10 now wants negotiations to "start promptly" - once the article is invoked it will be up to the European Union to come back, with an early response expected within 48 hours.
In Northern Ireland, which also voted to stay in the European Union, the largest Irish nationalist party Sinn Fein has said it wants a referendum on splitting from the United Kingdom and uniting with the Republic of Ireland "as soon as possible".
The Prime Minister will deliver her letter triggering Article 50 to President Tusk on the Wednesday, and deliver a statement to the House of Commons announce the move.
If negotiations all go according to plan then Brexit will be completed by March 2019, however if terms have not been fully decided before the deadline Britain can ask for an extension, but only with agreement of the all 27 member states.
Later this year, the United Kingdom government is expected to introduce legislation to leave the European Union and put all existing European Union laws into British law, known as the Great Repeal bill.