The Brexit bill has returned to the House of Commons. What happens once MPs vote it through?

GettyBoris Johnson

• The Brexit bill has returned to the House of Commons where Members of Parliament are rushing to pass it before the UK's deadline of leaving the EU on January 31.
• Once passed Britain will immediately face a series of new Brexit cliff-edges as it battles to secure a new trade deal with the EU before the end of the Brexit transition period in December.
• The bill will help define Britain's future for decades but will likely pass in short order with few significant amendments.
• Experts warn that the bill could store up problems for Britain's future.
• Visit Business Insider's homepage for more stories.

Members of Parliament return to Westminster from their Christmas break on Tuesday afternoon where they will restart the process of fulfilling Boris Johnson's pledge to take Britain out of the European Union by the end of January.

Johnson's newly-won 80 seat majority in the House of Commons means the bill should pass easily by the end of the month.

However, the incredibly tight timescale, both for scrutinising the bill and for securing a new trade deal with the EU by the end of 2020, means the prime minister could be storing up big problems for the months and years ahead.

Here's everything you need to know about the Brexit bill and what will happen next.

What is the Brexit bill?

GettyThe European Union (Withdrawal Agreement) Bill is a piece of legislation which is designed to put Britain's divorce deal with the EU into law. Once passed it will allow the United Kingdom to leave the EU and all of its institutions before formally beginning the process of forming new trading relationships with both Europe and the rest of the world.

Is this the same as Theresa May's deal?

ReutersBoris Johnson and Theresa MAyMostly. Theresa May tried and failed to pass a very similar bill through the Commons three times.

However, her non-existent majority and the commitment to keep the UK tied to EU trade and customs rules through the Brexit "backstop" meant she ultimately lost both her deal and her premiership.

When Johnson became prime minister, he renegotiated a modified version of her deal which will instead allow Great Britain to cut all ties with the EU, while keeping Northern Ireland in a closer relationship with the EU in order to prevent a hard border between Northern Ireland and the Republic. The agreement is controversial because it will inevitably force new customs checks between Northern Ireland and the rest of the United Kingdom on the Irish Sea, which is why the Conservatives' former governing partners the Democratic Unionist Party, withdrew its support.

What else has Johnson changed?

GettyJohnson has also dropped a number of commitments he made before the December general election which were designed to win over Labour MPs to his deal. In particular, he tore out his previous commitments to maintain workers' rights and environmental protections, as well as ripping up commitments to allow MPs a vote on whether to extend the Brexit transition period.

Does this mean Johnson is preparing to slash workers' rights?

Ben Stansall - WPA Pool/Getty ImagesThe truth is we don't know. The pre-election provisions on workers' rights were in reality only ever a fig-leaf for Labour MPs who wanted to back the deal. No parliament can ever bind a future one and as soon as Johnson won a majority he was free to do whatever he wanted with workers' rights, regardless of what was in this bill.

And while he may rip up workers' right he may instead choose to strengthen them. As Professor Anand Menon of the UK in a Changing Europe think tank tells Business Insider: "You've got to bear in mind that it's what the manifesto says about those things that matter.

"One of the interesting things about the Tory manifesto is that it's left the door ajar... to get beyond what the EU does in areas like workers' rights."

The government insists it will pass new legislation this parliament to further protect workers' rights. However, the detail remains sketchy and we will only know whether he actually will when that legislation is brought forward. What we do know is that the future of workers' rights will not be decided by this Brexit bill.

Will MPs make any more changes to the bill?

GettyThe bill will enter its committee stage on Tuesday when MPs will go through it line-by-line to see whether it requires any amendment. Lots of amendments will likely be put forward. However, unless there is a part of the bill which Conservative MPs en masse themselves suddenly have the desire to change, then it will likely travel through the House unchanged. One change that Conservative MPs do want to see is that the Big Ben bell, which is currently out of action due to refurbishment, should ring out on Brexit day. If House of Commons Speaker Lindsay Hoyle agrees to consider that amendment, which on the face of it seems unlikely given its tangential relationship to the main purpose of the bill, then there would likely be a majority for that change.

So we're 'getting Brexit done' by January 31 then?

GettyWell yes and no. Brexit will almost certainly technically take place by the end of the month. However, the UK will then immediately enter an 11-month transition period during which the country will for all intents and purposes remain a de facto member of the bloc. The UK will also immediately be up against three rapidly approaching a series of new Brexit deadlines. These are:

• March 1 2020: The UK must agree on a new negotiating mandate with the EU.
• July 1 2020: The UK must decide by the end of June to decide whether it requires an extension of the 11 month transition period, something Johnson has so far totally ruled out.
• November 26 2020: The UK must have agreed on a new trade deal with the EU by the final week of November to have any chance of ratifying it before the end of the year.
• December 31 2020: The Brexit transition will end. By this point, Johnson will either need to have agreed and ratified a new trade deal, agreed an extension or resigned to cutting off trade ties with its largest trading partner.

Will Johnson extend the new Brexit deadline?

GettyThe prime minister has insisted many times that he won't extend the transition period. However, he previously made similar "do or die" pledges about leaving the EU on October 31 and broke those without it harming his election prospects. Only a fool would rule out him doing the same again, particularly if the early part of talks get bogged down.

As Anand Menon tells Business Insider: "I suppose you could just about see the prime minister saying, 'The European Union is refusing to negotiate anything until we've done fish and financial services and we're reluctantly going to have to extend the transition period'."

Johnson has promised to legislate against any extension. However, as Maddy Thimont Jack, from the Institute for Government points out: "Boris Johnson has got a large majority but does he also have the numbers to potentially override that legislation later in the year? I don't see it as binding right now - I think it's a political statement."

Will everything go to plan?

GettyAfter three years of intense Brexit debate, the general election appears to have taken the heat out of the issue for now. However, before very long Britain will face a new series of cliff edges and more intense political debates about the country's new place in the world. With such little time to make these decisions and implement them, there is lots of room for things to go awry.

"There are absolutely legitimate concerns [about this] because actually it's a very, very complicated piece of law which affects a lot of technical areas, and there's a real danger of things going wrong," Menon says.

"Of not having thought things through properly, of doing things on the back of an envelope, of parliament ceding so much power to the executive that a lot of the serious business of reshaping the country post-Brexit will be done by statutory instruments rather than proper legislation, so it will escape any sort of scrutiny."

Maddy Thimont Jack, from the Institute for Government agrees. "It is so much faster than what you'd usually expect for such a constitutionally significant piece of legislation. With the Lisbon Treaty, it took 26 sitting days to pass legislation relating to it, but 200 calendar days.

"Usually you want time to take evidence from experts, for example, but they're having to operate in a much tighter time scale. A big part of the bill is implementing legislation relating to citizens' rights. Lots of civil society organisations are very concerned about this but there's very little time for them to get involved."

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