British Brexit negotiators are expected to launch fortnightly rounds of talks in Brussels from as early as this week.
EU diplomats say the aim is to agree a swift deal on a transition period.
UK Brexit Secretary David Davis outlined his view of a post-Brexit transition on Friday. He said he expected to start talks in the coming "days and weeks".
The next step
Ministers from the EU 27 have met to formally endorse instructions for Phase Two of the Brexit talks at a meeting in Brussels.
Sources say at that point, the EU negotiating team, led by Michel Barnier, will be ready to receive Davis and his officials for formal negotiations on what will happen after Britain breaks with Brussels in March 2019.
Davis says he is confident of reaching an interim accord on the transition by the time EU leaders hold a Brussels summit in March. There is already broad agreement, he added.
What are the transition talks likely to focus on?
These are talks about talks. The future of the customs union, regulatory convergence or divergence and trade are likely to dominate.
The status quo is complex. Will the UK get a non-voting seat at some EU meetings? How will annual quotas like that of fishing be determined? How will the EU allow London to sign up to new trade deals with other countries while bound by EU accords?
What does the EU want?
Brussels has proposed that the UK will effectively remain in all of its existing structures, including the single market and customs union, until the end of 2020.
However, the UK will lose its say on EU policy.
What has Theresa May said?
She appears to be ready to accept this. That's despite disappointment from Brexit supporters, who say it will turn the UK into a "vassal state" for a short time.
If it is an interim accord, will it be legally binding?
No. Details of the transition will form part of a withdrawal treaty which will be agreed around October-time. It will be legally ratified by parliaments on both sides in the month after that.
Both sides are hoping a joint declaration on the nature of the transition in March will give businesses and people more certainty to make decisions about their future.
So when will the first meeting be held?
It could be as early as this week, it is said. No formal schedule has been agreed so far, but diplomats say the plan for now is to set a relatively fast pace. This could mean meeting in Brussels every two weeks. This is compared to the monthly round of negotiations held in the first phase of the talks.
A first meeting could be held as soon as the latter part of next week, they said.
While no schedule for those talks has been formally agreed, EU diplomats said the plan for now is to set a relatively fast pace of exchanges, meeting in Brussels every two weeks in contrast to the roughly monthly round of negotiations held in the first phase of the process last year.
What they are saying