In the 2016 referendum, 52% of UK voters opted to leave the European Union. In Northern Ireland, however, 56% voted to remain. A major focus of Brexit negotiations under the May and Johnson Governments has been how to keep an open border between Ireland and Northern Ireland.

UK Government vision: May

After the referendum Theresa May’s Government set three main goals for Brexit and the Irish border:

  1. The UK to leave the EU’s Single Market and Customs Union. This would allow the UK to make its own rules on goods and services and make its own free trade agreements.
  2. No infrastructure at the Irish border or new checks on goods moving between Ireland and Northern Ireland.
  3. No trade barriers (like checks on goods) between Northern Ireland and the rest of the UK (often called ‘putting the border in the Irish Sea’).


Most trade experts said it would not be possible to do all three things and that only two of these goals could be met at the same time. As Figure 1 illustrates, trade-offs would be required and the Government would have to choose one of three difficult options:

  • Option A: Giving Northern Ireland a ‘special status’ – it would stay in the EU’s Single Market for goods and the EU’s customs union. This would mean checks on goods between Northern Ireland and Great Britain.
  • Option B: Infrastructure and checks on goods at the Irish border, often called a ‘hard border’.
  • Option C: Keeping the whole of the UK in the Single Market (at least for goods) and the Customs Union (or an alternative customs union).

Figure 1: Northern Ireland border trade-offs

Acknowledgements to R. Daniel Kelemen, Rutgers University

In reality, things are a little messier, with some mixing of the options possible. But the point remains that options are limited.

‘Alternative arrangements’ were looked at, such as technology to replace checks at the border. Most trade experts were doubtful that such arrangements could ever fully replace checks and Single Market rules. In any case, such methods might take several years to develop. So, for now at least, difficult choices were inevitable.

A hard border not an option

EU and UK political leaders largely agreed that Option B, putting up infrastructure and conducting checks at the border, was the worst outcome because of concerns that a hard border could lead to political unrest, and possibly even violence in Northern Ireland.

Senior leaders of the Police Service of Northern Ireland, the Irish Government, and the UK Government’s ‘no deal’ planning assumptions have all raised these concerns.

Some commentators doubt the link between changes to the border and the potential for political violence. Some Northern Ireland Unionist politicians argue that technology such as border cameras and drones would not represent a ‘hard border’.

Nevertheless, the ‘hard border’ is unpopular with the public in Northern Ireland. The EU, UK and Irish governments agree that they do not wish to put up infrastructure and/or checks at or around the border.

The ‘backstop’

After failing to persuade EU negotiators that her plans would solve the Irish border issue, Theresa May negotiated a new solution that became known as the ‘backstop’; this was essentially option C. The backstop, however, was not supposed to be the final solution but a temporary fix until the UK could find the elusive ‘fourth way’ (represented by the ‘?’ in Figure 1).

The backstop would have meant Northern Ireland following most Single Market rules for goods, as well as some on VAT, agriculture and the environment and the EU’s customs code. The entire UK would also have been part of a customs union with the EU, covering all goods (except for fish).

This would have limited the UK’s ability to make its own trade agreements. The UK would also have been subject to ‘level playing field’ restrictions, maintaining common standards with the EU in areas such as working conditions and the environment, as well as having to follow EU state aid and competition rules.

The backstop would have meant the Irish border remained open and would have enabled trade to continue without tariffs and customs checks between the UK and EU.

Under the backstop Great Britain could have started making its own rules on goods. But Mrs May said that Great Britain would remain “aligned” with EU rules as long as the backstop was in place, ensuring there would be no checks on goods moving from Great Britain to Northern Ireland.

In the end Parliament voted down Mrs May’s Withdrawal Agreement, opposing in particular the ‘backstop’.

Boris Johnson’s plan

When Boris Johnson became Prime Minister he pledged to remove the backstop. He said it was undemocratic and he wanted the Northern Ireland Assembly to agree to any new Withdrawal Agreement. He wanted the whole of the UK to leave the EU’s Customs Union at the end of the transition period, and Northern Ireland to remain part of the UK’s customs territory but to follow EU rules on goods.

This was essentially option A – a special status for Northern Ireland. It meant the customs border would be between Ireland and Northern Ireland.

The EU did not accept all these conditions, but Mr Johnson was able to change the Withdrawal Agreement significantly in respect of Northern Ireland.

The details

Under the terms of the new Withdrawal Agreement, Northern Ireland remains part of the UK customs territory, so Northern Ireland will be included in UK free trade agreements. Northern Ireland will also technically be part of the UK’s VAT area.

In practice, however, Northern Ireland will apply many EU customs rules and there will effectively be a customs and regulatory border between Great Britain and Northern Ireland in the Irish Sea.

The Northern Ireland Assembly will have an opportunity to vote periodically on whether this arrangement should continue. The first opportunity will be four years after the end of the transition period.

The other major difference is that Mr Johnson’s Agreement for Northern Ireland, unlike the backstop, is no longer temporary. It is, unless the Northern Ireland Assembly votes otherwise, the permanent end state for Northern Ireland.

The level-playing field rules that were part of the backstop are not part of the new Agreement. However, the trade relationship between Great Britain and the EU is still to be agreed; the EU is likely to request that the UK sign up to similar guarantees.


Mr Johnson’s renegotiated Withdrawal Agreement quickly gained the support of Conservative MPs, many of whom had been unhappy with the backstop. Northern Ireland’s Democratic Unionist Party believes that the proposals are not beneficial to the economic well-being of Northern Ireland and that they undermine the integrity of the Union. Sinn Féin, the SDLP and the Alliance Party, who all opposed Brexit, have rejected the deal, and in particular the consent mechanism.

What is still to be decided?

There remain questions about how exactly goods will move between Northern Ireland and Great Britain.

  • Will paperwork such as customs declarations be required?
  • To what extent will goods have to be checked?
  • How different will the regime be for goods going from Great Britain to Northern Ireland compared with those going in the other direction?

The Withdrawal Agreement provided a high-level blueprint without setting out the exact details of how trade across the Irish border and between Great Britain and Northern Ireland will work. The detail will be worked out in discussions between the EU and the UK once the UK has left and the transition period starts.

What checks will be required?

It is clear that goods travelling from Great Britain to Northern Ireland will require paperwork and checks. The Government’s impact assessment states that two forms  – import declarations and entry summary declarations – will be required for these goods, and that they will undergo regulatory checks as well.

The situation for goods moving from Northern Ireland to Great Britain is less clear. Stephen Barclay, Secretary of State for Exiting the EU, told Parliament in October 2019 that the new Withdrawal Agreement allows the United Kingdom to ensure “unfettered market access for goods moving from Northern Ireland to Great Britain.” He also said that there will be “minimal targeted interventions” to goods moving from Northern Ireland to Great Britain.

Boris Johnson and Northern Ireland Secretary Julian Smith have since said there would be no extra costs, checks or administration on goods moving from Northern Ireland to Great Britain.

The new Withdrawal Agreement will apply the EU customs code to Northern Ireland. Professor Alan Winters, director of the UK Trade Policy Observatory at Sussex University, believes that the code requires documentation for goods being exported from Northern Ireland to Great Britain, unless the EU grants an exception or waiver. But he says procedures would be “fairly light.”

What next?

The longer the transition period, the longer the two sides will have to work out exactly how the Irish border will function (see Brexit: What happens next? for more on transition).

Any government that wants to change the parts of the Withdrawal Agreement that deal with the Irish border will have to tackle the same trade-offs as its predecessors.

Political divisions in Northern Ireland and the wider UK mean a significant minority will probably be unhappy with any outcome that such trade-offs create.

Further reading

Insights for the new Parliament

This article is part of our series of Insights for the new Parliament. This series covers a range of topics that will take centre stage in UK and international politics in the new Parliament.