Britain’s protracted divorce from the European Union is finally happening: It will leave the bloc at 11 p.m. London time (midnight in Brussels) on Jan. 31. But that finish line is also a starting line for the battle over how the separation will work in practice. Virtually all facets of business and everyday life will remain unchanged while the U.K. and EU hash out specifics on issues ranging from trade to data sharing, fishing rights, and security co-operation. The new deadline is Dec. 31, 2020 -- an ambitious one given that such deals usually take years to hammer out.

1. Isn’t Brexit done yet?

Just about. It was a done deal after the game-changing U.K. election on Dec. 12, when Prime Minister Boris Johnson’s Conservative Party won a whopping 80-seat majority and a mandate to get it done. Parliament’s passage of the Withdraw Agreement Bill on Jan. 23 avoids a disorderly or “no-deal” Brexit, and allows for an 11-month transition to Britain’s life on the outside. During that time, the U.K. will still trade freely with the EU and be subject to most of its laws, even though it will have no say in making them.

2. What will Brexit look like at first?

The U.K. has already updated the cover of newly issued passports, but other changes this year will be harder to see:

• Free movement of EU and British citizens into and out of the bloc will remain the same during the transition period; no changes at border crossings or to mobile phone roaming charges.

• A deal protecting the rights of more than 3 million EU citizens living in the U.K. and about a million British citizens residing in the bloc will come into force. The agreement allows them to stay where they are and continue to enjoy pensions and access to health care where they live.

• Britain will pay its divorce bill, meeting obligations it made to the EU while a member. That could total about 33 billion pounds ($43 billion).

• Plans to prevent a hard border on the island of Ireland will be set in motion, though won’t come into force until the end of the transition period.

3. What remains unsettled?

The Brexit legislation doesn’t touch the far bigger question of the future relationship between the EU and U.K. after the end of the transition period in December. In theory, the two sides will have signed a free-trade agreement by then -- but that’s a matter of political negotiation. If you’re, say, working for a Japanese company with a base in London that’s exporting to the EU, you’ve still got no certainty about the terms of trade across the English Channel at the start of 2021. Expect more political wrangling in the months ahead, along with talk that Britain may be trying to transform itself into a low-regulation “Singapore-on-Thames.”

4. What does ‘Singapore-on-Thames’ mean?

It’s code for the post-Brexit U.K. looking more like the “light touch” regulatory regime found in the Asian city-state. Johnson moved the U.K.’s commitments to abide by EU standards on tax, labor rights and the environment out of the legally-binding portion of the Brexit deal and into the separate, non-binding political declaration. That gives him greater freedom to diverge from EU norms after Brexit -- but it could also make a comprehensive trade deal with the EU much harder. French President Emmanuel Macron neatly summed up the problem the British will face: “Every time they depart from EU regulations, they will stray away from an ambitious accord,” he told reporters in the hours after Johnson’s victory. Brussels is hardly going to allow the U.K. access to its single market of 500 million people and, at the same time, let it undercut the competitiveness of its members.

5. What if they can’t reach a deal by the end of 2020?

EU negotiators have warned the December 2020 deadline is unrealistic. Johnson has ruled out prolonging the transition period -- although he has changed his mind before. If the EU and U.K. don’t come to an agreement, the U.K. could “crash out” at the end of the transition period and revert to trading with the EU on commercial terms negotiated in 1995 by members of the World Trade Organization. It would look much like a no-deal Brexit. Better that, say hard-line Brexiters, than being subject to EU laws with no say over deciding them. The crunch moment will come ahead of a July 1 deadline to seek an extension.

6. So what kind of deal is possible?

More likely, Britain could seek to do a quick and dirty deal ensuring zero tariffs and quotas on goods, something suggested by Ivan Rogers, the U.K.’s former ambassador to the EU. Because the EU enjoys a goods surplus with the U.K., that might actually help German car manufacturers. But a deal on goods that excludes services, where the U.K. has a big surplus with the EU, could hurt the City of London’s financial industry in particular.

To contact the reporter on this story: Edward Evans in London at eevans3@bloomberg.net

To contact the editors responsible for this story: Flavia Krause-Jackson at fjackson@bloomberg.net, Leah Harrison Singer, Thomas Penny

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