After European Union leaders agreed Friday to begin talks on the blocs future relationship with Britain, here is an outline of what we know so far about the UKs departure from the EU:
Following Britain's vote to leave the EU in a June 2016 referendum, Prime Minister Theresa May officially gave notice to the 28-member bloc on March 29.
This set the clock ticking on a two-year process that should see Britain withdraw on March 29, 2019.
Negotiations with Brussels began in June, focused on three issues: the financial settlement, EU citizens' rights and the Irish border.
EU leaders demanded "sufficient progress" on these matters before allowing the discussion to shift to trade.
After stalled attempts and setbacks for May, particularly on Irish border matters, EU leaders endorsed an interim deal on the divorce terms.
Michel Barnier, the European Commission's Brexit negotiator, wants the full negotiations wrapped up by October 2018 to give the EU Parliament time to ratify any final deal.
In a speech in Florence in September, May confirmed Britain would seek a time-limited "implementation period" to give businesses certainty as they prepare for Brexit.
It would last "around two years", although this loose phrasing has caused divisions in the British cabinet.
May has said Britain intends to leave the European single market in order to end the free movement of people from the continent.
But the relationship would stay largely the same during the transition period.
The EU on Friday said negotiations on the transition period would start in January but Britain would have to respect the full complement of EU laws during it.
Talks stalled on the issue of money, so May said in Florence that Britain would honour commitments made during its membership up until the end of the current budget cycle in 2020.
It would also pay towards future joint programmes on security and scientific research.
Britain's Brexit negotiator David Davis said that Britain would not honour its £35 billion to £39 billion (40-45 billion euros, $47-$52 billion) divorce bill as agreed earlier this month if it fails to secure a future EU trade agreement.
The status of more than three million Europeans living in Britain, and more than one million British expatriates, is a key issue for both sides.
The first stage agreement sets out residency rights and benefits available to more than three million EU citizens living in Britain and another one million of its citizens living in the EU.
The deal guarantees the post-Brexit rights of Britons already living in the bloc and of their EU counterparts based in Britain with family members able to claim residence.
Neither the EU nor Britain want customs posts returned to the border between Northern Ireland and Ireland.
In the agreement, Britain says it "remains committed to protecting North-South cooperation and to its guarantee of avoiding a hard border" between the two.
If that proves impossible, Britain will propose "specific solutions to address the unique circumstances," including alignment with the internal market and the customs union rules.
As well as leaving the single market, May says Britain would leave the EU's customs union so that it can strike its own trade deals with countries outside the bloc.
She has rejected joining the European Economic Area or signing a traditional free trade agreement.
The EU wants "clarity" on what Britain wants before embarking on full negotiations and says this can only happen from March next year.
Davis has called for a "Canada plus plus plus" deal, referring to the trade agreement struck between Brussels and Ottawa.
May has repeatedly said she would rather walk away rather than accept a bad deal, while Davis has said Britain paying a financial settlement depends on a satisfactory full deal.
Without a new trade agreement, Britain would fall back on World Trade Organization rules, which could mean higher export tariffs and other barriers.
May suffered a humiliating parliamentary defeat on Wednesday when MPs voted to give parliament final approval on the separation. A small number of rebels in her Conservative Party were enough to trigger the loss.
She is reliant on the support of Northern Ireland's Brexit-backing Democratic Unionist Party for a majority in the House of Commons, but could face future trouble from the now-emboldened rebels.