With one year to go, here's what you need to know about Brexit

It is a year to go until Brexit.

The UK will formally depart the EU on Friday 29 March 2019 (at 11pm GMT) - although the transition to the new reality means we won't actually be EU-free until the first day of 2021.

So what has been agreed upon, what is still to be negotiated and how will it affect all four nations (two of whom, remember, never voted for it)?

Here's a speedy guide to exactly where we are at with Brexit so far...

What has already been decided?

Chief negotiators David Davis and Michel Barnier highlighted the 'green lines' of agreement on the withdrawal. Credit: PA

Officially nothing beyond the terms of transition.

However, there's provisional agreement on several of the key early 'divorce' issues, namely: money, citizens' rights and the Irish border.

The sides are apparently settled on how much the UK will pay to split with the EU, though the final figure - estimated to be at its lowest £40bn - is still unknown.

A provisional agreement to preserve and protect the future rights of UK citizens living in the EU and EU citizens living in the UK is "complete".

And there is a guarantee that a hard border will not be imposed between Northern Ireland and the Republic of Ireland.

While it's still a point of negotiation, the sides agree if no deal is struck, the single market rules (essentially no tariffs for trade) will continue across the border until a new arrangement is decided.

So what still needs to be negotiated?

This working farm in Hampshire exports its Aberdeen Angus beef to 56 countries, including many in the EU. Credit: PA

All of the above needs to be worked into a fixed final withdrawal agreement, including all the legal and political ramifications of Britain's EU exit.

But the big issue now to be thrashed out is Britain's new trading relationship to replace the existing free trade with the EU bloc.

The UK government intends to leave the single market and customs union, so must determine mutually beneficial new trade terms.

New migration rules must also be decided, with the end of free access to the EU also ending the free movement of people across British borders.

The terms of the future partnerships on shared security, defence and other foreign policy issues must be worked out.

And the new way the UK and EU will work together in fields including research, education and transport.

The key dates in the road to Brexit and beyond:

  • 23 June 2016 - Referendum delivers 52%-48% vote to leave.

  • 29 March 2017 - UK triggers Article 50 of the Lisbon Treaty to begin the formal withdrawal.

  • 19 June 2017 - Brexit negotiations begin.

  • 8 December 2017 - Provisional deal on 'divorce' issues agreed upon.

  • 19 March 2018 - UK and EU hail 'green lines' in transition deal to pave the way for trade talks.

  • 18-19 October - The target date to agree on the final text of the withdrawal treaty.

Britain will wave goodbye to the EU in two stages. Credit: PA
  • January 2019 - The targeted month for the withdrawal terms to be ratified by the EU and UK.

  • 29 March 2019 - British membership of the EU ends at 11pm GMT and midnight in Brussels.

  • 30 March 2019 - The 21-month transition period begins, during which Britain can negotiate (but not ratify) future trade deals with non-EU partners.

  • 31 December 2020 - The transition period ends.

  • 1 January 2021 - A new EU-UK free trade deal will be installed, while any other trade deals with external partners can be ratified.

What undecided issues affect the home nations?

The sides must still determine how to run a soft border between Northern Ireland and the Republic. Credit: PA

The biggest 'home nations issue' is how to manage the Northern Ireland-Republic of Ireland soft border and whether to retain a role for the European Court of Justice in border concerns.

While Britain's future trading arrangements will impact all the home nations (despite only England and Wales majority voting to leave), there are issues specific to each one which still need to be resolved.

In particular, which powers from the EU will be handed to the devolved governments and how the UK will fill funding gaps for key industries, for example Welsh farming or Scottish and English fishing.

The application of EU law surrounding VAT and excise duties, agriculture, fisheries products and environmental protection will affect all four nations.

What needs to be passed for Brexit to happen?

MPs have secured the right to vote on the final Brexit deal struck. Credit: PA

The government needs to see its European Union (Withdrawal) Bill through Parliament and into law.

The Commons and Lords have won the right to vote on the final deal for it to be passed.

What happens if there's no deal or if MPs reject it?

The UK would be forced to trade with the EU under World Trade Organisation rules, which would bring high tariffs and costly custom check delays, until a deal is worked out.

The living status of EU nationals already in the UK and British citizens in EU nations would be unaffected.

Assuming a deal is struck, what happens in the 21-month transition period?

From 29 March 2019 until 31 December 2020 businesses and other bodies will adapt to the agreed post-Brexit rules, while the free movement of people will continue.

Britain will still pay into the EU and make good on all obligations as a member, while retaining access to the single market, but will lose voting rights.

The UK can also begin trade negotiations with other nations, but they won't take affect until the transition formally ends on New Year's Day, 2021.