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Boris Johnson is expected to present his 'final offer' Brexit proposals to the EU in the coming days as he tries to secure a deal before the October 31 deadline.
The Prime Minister will submit a formal plan setting out how the UK believes the Irish border backstop can be replaced.
Today it emerged that the PM's proposed way forward could include the introduction of so-called 'customs clearance centres' away from the border.
But how would they work and are they actually a part of the government's thinking?
All of the key questions are answered below as the battle for Brexit enters its final phase.
In broad terms, what is the plan to replace the backstop?
Mr Johnson's proposals are expected to be based on establishing a so-called all-Ireland 'economic zone'.
This zone would allow certain items to move across the Irish border without any checks because both sides would stick to the same rules and regulations in terms of how the goods are produced.
It is thought that agricultural, food and industrial goods could be included in the proposed 'economic zone' plan to allow them to be moved without any friction.
The plan is also thought to include a proposal to give the Northern Irish Assembly a say on which rules and regulations are applied - a so-called 'Stormont Lock'.
How Boris Johnson's reported Brexit plan could work: 'Customs clearance centres' could be set up near the Irish border
Mr Johnson, pictured in Manchester today, is reportedly going to ask the EU to agree to a backstop replacement proposal which would involve the creation of 'customs clearance centres'
The idea of building customs posts near the Irish border was given short shrift by the Irish government
Such a provision has long been floated by the DUP as one of the party's negotiating red lines because it would effectively give political parties in Northern Ireland the ability to veto the application of certain EU rules or proposed changes.
However, the proposed 'economic zone' will not solve all of the problems associated with the border and the government is reportedly still saying that other issues will have to be addressed through 'alternative arrangements' and new technology.
That could included trusted trader schemes and exemptions for small businesses, according to The Telegraph.
But the big development overnight is that Mr Johnson reportedly wants to set up customs checkpoints on both sides of the border.
However, the customs posts would not be located at the crossing itself but five to 10 miles away.
How would the customs posts plan work?
According to RTE News in Ireland, the UK's offer will propose establishing 'customs clearance centres' on both sides of the border.
These customs posts would be located between five and 10 miles away from the crossing.
The proposals were apparently floated during recent discussions between the UK and the EU but it has now been claimed that they do form part of Mr Johnson's formal offer.
They would see lorries carrying goods produced in sectors where the EU and UK are no longer aligned potentially having to check into the 'customs clearance centres' where they would declare what they are moving.
The extent to which there would be formal customs checks or inspections is unclear but it is thought most of that work would be undertaken where the goods originated from - potentially before they leave the farm or factory gates.
After checking in, the lorries heading either north or south would then be monitored electronically - potentially using tracking devices fitted on vehicles or by GPS - as they cross the border before checking into the corresponding customs post on the other side and then continuing to their destination.
Such an approach would ensure there is no physical infrastructure built at the border itself - something Mr Johnson has said he will never agree to.
But it would mean physical infrastructure being built somewhere and that will likely be enough for the the EU and Dublin to reject the plan amid fears the customs sites could become targets for terrorists.
It is unclear how big physically, or how time consuming, such a system could prove to be, but proposing building any infrastructure anywhere near the border will be hard for the EU to accept.
It sounds like this would create a regulatory border in the Irish Sea? Is that right?
By keeping Northern Ireland aligned with the EU in certain areas like food and agricultural goods, there would be a small regulatory border created in the Irish Sea.
The so-called Irish border backstop is one of the most controversial parts of the existing Brexit deal. This is what it means:
What is the backstop?
The backstop was invented to meet promises to keep open the border between Ireland and Northern Ireland even if there is no comprehensive UK-EU trade deal.
The divorce deal says it will kick in automatically at the end of the Brexit transition period if that deal is not in place.
It effectively keeps the UK in a customs union with the EU and Northern Ireland in both the customs union and single market.
This means many EU laws will keep being imposed on the UK, restricting its ability to do its own trade deals. It also means regulatory checks on some goods crossing the Irish Sea.
Why have Ireland and the EU demanded it?
Because the UK is leaving the customs union and single market, the EU said it needed guarantees that people and goods circulating inside its border - in this case in