Sterling declined by 0.23 percent to a day-low of $1.2367 after the announcement, ending a run of steady gains, Bloomberg reported.
Prime Minister Theresa May’s spokesman had earlier confirmed the date for the official triggering of Article 50 as 29 March.
It represents the commencement of the formal process of withdrawing from the EU and can last a maximum of two years.
One trader, who spoke anonymously to the financial news service, said demand for the dollar was also impacting negatively on the pound.
Sterling also declined against the Euro by 0.20 percentage points initially.
Fluctuation in the value of the pound against both the Euro and US dollar has been blamed for increasing prices in shops.
British envoy to the EU, Sir Tim Barrow, informed the European Council earlier on Monday of the UK’s official decision to invoke the withdrawal mechanism under the Lisbon Treaty.
Once Article 50 is triggered, Council President Donald Tusk is expected to provide an initial response to the Prime Minister within 48 hours, and the remaining EU 27 countries will then put together a timetable for negotiations on the UK’s withdrawal to take place.
Downing Street said: “We want negotiations to start promptly, but it’s obviously right the 27 have an opportunity to agree their position.”