Parliament will sit on a Saturday for the first time in 37 years to debate Boris Johnson’s Brexit deal, which he made with the European Union on Thursday.
If the deal is approved, Mr Johnson will have met his goal of leaving the EU by October 31 “do or die, come what may”.
If not, he has maintained the only other option is to leave with no deal.
So what is on offer in the Prime Minister’s deal, and how does it differ from the agreement that Theresa May failed to pass three times?
The backstop was a major sticking point for Mr Johnson, who argued it left Northern Ireland trapped in the EU customs union.
Under his deal, the whole of the UK leaves the EU customs union, with customs checks instead taking place at ports when goods enter Northern Ireland.
Despite this, Northern Ireland would stick to the EU’s regulations on goods instead of the UK’s as there would be an “all-island regulatory zone” in the island of Ireland.
It would mean goods travelling between Ireland and Northern Ireland could move relatively freely, but some goods moving between Northern Ireland and the rest of the UK would need to be checked.
This arrangement could stay in place indefinitely if the UK, EU and Northern Irish Parliament fail to find an alternative.
The Transition Period
Under Mr Johnson’s deal the UK would leave the EU on October 31, but would remain under EU laws until December 2020 while their future relationship was negotiated.
The UK would follow EU rules and pay membership fees to the EU, but would no longer have a say over institutions such as the European Parliament of the European Central Bank.
This has not changed from Mrs May’s thrice-failed deal.
UK citizens would be able to live and work in the EU after October 31, and EU citizens would have the same rights in the UK. They would retain freedom of movement during the transition period.
After 2020 UK nationals seeking to live in the EU would need to follow that country’s immigration rules. This is a holdover from Mrs May’s deal.
One of the major criticisms of Mrs May’s deal was the £39 billion ‘divorce bill’, which paid the UK’s EU membership fees until the end of 2020.
In August Mr Johnson suggested the UK would not owe anything if it left without a deal, however the accuracy of this claim remains unclear.
Under Mr Johnson’s deal the UK would pay around £33 billion to leave, with the majority of this paid by 2022.
However, this was not due to hard bargaining from the Prime Minister, but instead because the UK had continued to pay the EU since it was supposed to leave in March.