EU ambassadors on Monday unanimously backed the hard-fought Brexit deal with the UK amid warnings of disruption when a new era of relations between the two sides begins this week.
The agreement covering trade worth £660 billion ($895bn) was struck on December 24 and is expected to be passed by the UK Parliament on Wednesday.
The country is moving to a complete break from European institutions after 48 years of membership.
The ambassadors, representing the 27 EU nations, swiftly approved the deal on Monday, clearing the way for way for it to come into effect in the New Year.
London's stock exchange was closed on Monday but other European markets rose as investors welcomed the deal and a US stimulus package.
British Minister for the Cabinet Office Michael Gove warned of “bumpy moments” ahead as businesses made final preparations for new arrangements that will increase red tape after leaving the EU single market and Customs union.
“The nature of our new relationship with the EU … means that there are practical and procedural changes that businesses and citizens need to get ready for,” Mr Gove told the BBC.
Practical changes include phasing out a European health insurance plan and possible changes to mobile phone roaming charges.
“We know that there will be some disruption as we adjust to new ways of doing business with the EU, so it is vital that we all take the necessary action now,” Mr Gove said.
Members of Parliament are expected to pass the legislation after the opposition Labour Party gave qualified support for it.
Labour said it was “thin” and needed more work to protect British jobs, but it was backing the agreement to avoid leaving the EU without a trade deal.
The most hardline pro-Brexit MPs are also set to give their verdict on the agreement on Tuesday and are expected to back it.
But the most ardent Brexit critics said they would only abstain, to avoid throwing the UK’s relationship with the EU into greater chaos from January 1.
There is still opposition to the deal, notably from the UK’s fishing industry.
It said the deal would leave some trawlermen worse off under the agreement.
The deal will increase the proportion of fish in UK waters but will stop trading between UK and EU fleets that allowed for increased income.
The issue of fishing rights was one of three key sticking points in the talks that delayed an agreement between the EU and Britain until December 24.
Andrew Locker, chairman of the National Federation of Fishermen's Organisations, said he felt “angry, disappointed and betrayed".
“We are absolutely worse off,” Mr Locker told the BBC. “What we have got now is a fraction of what we were promised through Brexit. We are going to really, really struggle this year.”
The deal over fishing rights also stoked discontent among politicians who support independence in Scotland, which has the largest share of the UK’s fishing quota.
The Scottish government is pushing for a new ballot after Scots in 2014 voted to remain part of the UK.
Scotland's First Minister Nicola Sturgeon said the ruling Conservative Party "sold out Scottish fishing all over again" with the new arrangements.
Other key questions remain over workers’ rights, environmental standards and access to EU markets for the UK’s vital financial services sector.
UK Finance Minister Rishi Sunak sought to reassure the industry at the weekend that it would not be harmed by the deal, despite having to do things a “bit differently” in coming years.