Rejoining the EU: How a UK Return Could Work

Last reviewed: October 2026

Rejoining the European Union would not mean simply reversing the legal steps that took the United Kingdom out of the EU. The UK is now a non-member country, so any future return would require a new application for membership and a new accession agreement.

This page explains the legal process, the political decisions that would be required, and the questions that would need to be negotiated if a future UK government decided to seek EU membership.

Rejoining the EU at a Glance

A future UK return to the EU would require a new application, negotiations and agreement on the terms of membership.

Legally Possible

Article 49 provides a legal route for a European state to apply for EU membership.

Not Automatic

The UK’s former membership and previous special terms would not simply be restored.

New Accession Terms

The UK would have to negotiate a new accession agreement and the terms applying at that time.

Agreement Required

All EU Member States would have to agree, and the European Parliament would need to consent.

Could the UK Apply to Rejoin the EU?

Yes. Article 49 of the Treaty on European Union allows any European state that respects the EU’s values and is committed to promoting them to apply for membership.

The UK would therefore be legally entitled to submit a new application. However, its previous membership would not automatically be restored. The UK would have to go through the EU accession process and agree new terms of membership with the existing Member States.

There is no separate treaty procedure that automatically gives a former Member State its previous membership terms back.

Sources: EUR-Lex - Article 49 of the Treaty on European Union | House of Commons Library - Debate on the UK Applying to Join the European Union

The First Step Would Be a UK Political Decision

Before making an application, the UK government would have to decide that seeking EU membership was its policy.

As of October 2026, the current UK Government’s stated policy is not to rejoin the EU. Instead, it has pursued a closer relationship with the EU while remaining outside the Union, the single market, and the customs union.

A future government could adopt a different policy, but applying for EU membership would require a deliberate political decision by the UK rather than an automatic legal process.

Sources: UK Parliament - Government Response to Petition on Rejoining the EU | GOV.UK - The UK's Trade Strategy

Step 1: Submit an Application Under Article 49

A formal application for EU membership would be addressed to the Council of the European Union.

Article 49 requires the Council to act unanimously after consulting the European Commission and receiving the consent of the European Parliament. National parliaments of the Member States and the European Parliament must also be notified of the application.

The application itself would therefore begin a process. It would not guarantee candidate status, the opening of negotiations or eventual membership.

Sources: EUR-Lex - Article 49 of the Treaty on European Union | European Parliament - Accession Procedure

Step 2: Meet the Membership Criteria

Countries seeking EU membership are expected to satisfy the Copenhagen criteria.

These include stable institutions guaranteeing democracy, the rule of law, human rights and respect for minorities; a functioning market economy capable of dealing with competition inside the EU; and the ability to take on and implement the obligations of EU membership.

Applicants must also be able to apply the EU’s body of law, often called the acquis communautaire or simply the EU acquis.

The UK already has a long history of applying EU law because of its previous membership, but the accession process would examine the law and institutions in place at the time of any new application. Areas in which UK and EU rules had diverged would form part of that assessment.

Sources: European Commission - Enlargement | Council of the EU - How EU Enlargement Works

Step 3: Candidate Status and Accession Negotiations

If the Member States agreed to move the application forward, the UK could become a candidate country and formal accession negotiations could begin.

Accession negotiations examine whether the applicant is ready to implement EU law and fulfil the obligations of membership across the full range of EU policy areas. The European Commission monitors progress and makes assessments during the process.

Important decisions during enlargement require the agreement of all EU Member States. The process is therefore not simply a negotiation between the UK and the European Commission: every Member State has a role.

There is no fixed timetable for completing accession negotiations. Progress depends on the applicant meeting the membership conditions and on political agreement among the Member States.

Sources: Council of the EU - How EU Enlargement Works | European Commission - Enlargement Countries

Step 4: Agree the Terms of Membership

If negotiations were successfully completed, the conditions of UK membership would be set out in an accession treaty.

This treaty would specify the terms on which the UK joined and any transitional arrangements or special provisions that had been agreed.

Article 49 requires the accession agreement to be agreed between the applicant country and the existing Member States. The European Parliament must consent, and the Council must approve the accession unanimously.

Every existing EU Member State and the applicant country must then ratify the accession treaty according to their own constitutional procedures.

Only after that process had been completed would the UK become an EU Member State again on the date specified in the treaty.

Sources: EUR-Lex - Article 49 of the Treaty on European Union | Council of the EU - How EU Enlargement Works

Questions a Future UK Application Would Have to Address

A new application would raise several important questions because the UK’s former special arrangements would not automatically return.

Previous Opt-Outs

The UK’s former special terms would not automatically be restored. Any new arrangements would have to be negotiated.

The Euro

Standard accession rules would apply unless different terms were agreed. Joining the EU would not mean replacing the pound immediately.

Schengen & the CTA

The UK’s former Schengen opt-out would not automatically return. Future arrangements would need to address Schengen and the Common Travel Area.

Another Referendum?

EU law does not require the UK to hold a referendum before joining. Whether to hold one would be a UK political decision.

Would the UK Get Its Old Opt-Outs Back?

Not automatically.

Before Brexit, the UK had a number of special arrangements that distinguished its membership from that of many other EU countries. These included an opt-out from adopting the euro, arrangements relating to the Schengen area and justice and home affairs, and the UK budget rebate.

Those arrangements were attached to the UK’s former membership. A new application would not automatically revive them.

Any special terms would have to be negotiated as part of a new accession agreement and accepted by the existing Member States. It therefore cannot be assumed that the UK would recover its former opt-outs.

Source: House of Commons Library - Debate on the UK Applying to Join the European Union

Would the UK Have to Adopt the Euro?

Under the EU’s current rules, all Member States except Denmark are in principle required to adopt the euro once they meet the necessary economic and legal conditions.

The UK previously had a treaty opt-out from this obligation. That opt-out ended with the UK’s membership and would not automatically return with a new application.

Under the standard accession framework, a newly joining UK without a newly negotiated opt-out would therefore be expected to commit to adopting the euro once the convergence criteria were met.

That does not mean the pound would have to disappear on the day of EU accession. Non-euro Member States can remain outside the euro area until the required conditions for adoption have been satisfied.

Whether the UK could negotiate a new euro opt-out would be a matter for accession negotiations and unanimous agreement; it cannot be assumed in advance.

Sources: Council of the EU - Joining the Euro Area | House of Commons Library - Debate on the UK Applying to Join the European Union

What About Schengen and the Common Travel Area?

The UK’s former EU membership included special arrangements that kept it outside the passport-free Schengen area.

Most EU Member States are now part of Schengen. Countries joining the Schengen area have to apply the Schengen rules, meet the required conditions and pass evaluations before internal border controls can be removed.

Ireland remains outside the Schengen area and maintains the Common Travel Area with the United Kingdom, allowing British and Irish citizens to move freely between the two countries under separate arrangements.

If the UK sought to rejoin the EU, its previous Schengen opt-out would not automatically return. The future relationship between EU membership, Schengen and the Common Travel Area would therefore be one of the issues to be addressed in the accession negotiations.

Sources: Council of the EU - The Schengen Area Explained | House of Commons Library - Debate on the UK Applying to Join the European Union

What Would Membership Change Again?

EU membership would place the UK inside the EU’s legal and institutional system rather than maintaining the relationship through agreements between two separate parties.

Subject to any transitional arrangements contained in an accession treaty, membership would include participation in the EU single market and customs union, representation in EU institutions, voting rights in the Council, elected Members of the European Parliament, and the rights and obligations associated with EU citizenship and free movement.

The UK would also once again be required to implement EU law in the areas covered by the treaties and accept the institutional and judicial arrangements that accompany membership.

The exact financial contribution, transitional measures and any specially negotiated provisions would depend on the final accession agreement.

Sources: European Commission - Enlargement | Council of the EU - EU Enlargement

Would There Have to Be Another Referendum?

EU law does not require an applicant country to hold a referendum before joining the European Union.

Whether the UK held a referendum would therefore be a domestic constitutional and political decision.

A future government and Parliament could therefore decide to hold a referendum before an application, during negotiations or on the final accession terms, but a referendum is not itself a requirement of Article 49.

Sources: EUR-Lex - Article 49 of the Treaty on European Union | House of Commons Library - Referendums in the UK

How Long Would Rejoining Take?

There is no fixed legal timetable.

EU accession is a multi-stage process involving an application, assessment of membership criteria, negotiations, unanimous decisions by the Member States, consent from the European Parliament and ratification of an accession treaty.

The UK’s previous EU membership could be relevant to the practical assessment of its laws and institutions, but it would not remove these legal stages.

The length of any future process would depend on the UK’s level of alignment with EU rules at the time, the matters requiring negotiation, the terms sought by the UK, and political agreement among all Member States.

It is therefore possible to describe the steps required, but not to state reliably how many years a future UK accession process would take.

Sources: Council of the EU - How EU Enlargement Works | European Commission - Enlargement

Rejoining the EU Is Different From a Closer Partnership

The UK can develop a closer relationship with the EU without becoming a Member State.

The agreements reached and negotiated since Brexit demonstrate several possible forms of closer cooperation, including participation in EU programmes, security cooperation, sector-specific agreements and greater regulatory alignment.

None of these arrangements by itself amounts to EU membership. Membership would require the separate accession process described above and would bring the UK back inside the EU’s institutions, treaties and legal framework.

This distinction is important when discussing proposals such as closer single-market cooperation, a customs agreement, participation in EU programmes or full EU membership. They are legally different models.

Sources: GOV.UK - The UK's Trade Strategy | European Commission - Relations with the United Kingdom

What Would Have to Happen in Practice?

A future route back to EU membership would therefore require several separate decisions:

1. A UK government would have to decide to seek membership.
2. The UK would submit an application under Article 49.
3. The EU Member States would have to agree unanimously to advance the process.
4. The UK would need to satisfy the membership criteria and complete accession negotiations.
5. The UK and EU Member States would negotiate the detailed terms of membership.
6. The European Parliament would have to give its consent.
7. Every EU Member State and the UK would have to ratify the accession treaty.
8. Any UK referendum, if one were chosen, would require separate UK legislation.

None of those stages predetermines the result of the next one.

Rejoining is therefore legally possible, but it would be a new accession process based on the political choices and treaty terms existing at that time.

Where to Explore Next

Continue exploring how Brexit happened, what changed after the UK left the EU, and how the UK–EU relationship is developing today.

Rejoining the EU