Brexit and the UPC: where British patent holders now stand

The United Kingdom signed the Agreement on a Unified Patent Court, then withdrew from it before it entered into force. It remains a party to the European Patent Convention. That intermediate position is no institutional curiosity: it governs the way a British proprietor obtains, defends and may lose its rights in Europe.

A procedural legacy left at the door

The procedure of the Unified Patent Court owes a great deal to the common law tradition. Front-loaded pleadings, the role of the judge-rapporteur and the logic of swift provisional measures are among the features the British negotiators helped impose. The Agreement kept them. The United Kingdom is no longer a contracting party. No local division sits on its territory and it holds no seat in any organ of the Court.

Scale does the rest. A decision of the Court takes effect across all contracting member states. A decision of the High Court stops at the British border. For standard essential patents, network technologies and medicines, that difference weighs more than the acknowledged quality of the English judge.

What Brexit did not change

TheEuropean Patent Office is not an institution of the European Union. It still grants brevets européens designating the United Kingdom, under the same procedure as before 2020, and opposition remains open on the same terms. A British applicant therefore retains full access to the European grant route.

Everything that changed lies downstream of grant.

Representation, the first lock

Article 48 of the Agreement reserves representation before the Court to lawyers authorised to practise before a court of a contracting member state, and to European patent attorneys entitled to act before the European Patent Office who hold an appropriate qualification, such as the European Patent Litigation Certificate. A solicitor admitted only in England and Wales falls into neither category.

The consequence is operational before it is symbolic. British firms intending to follow their clients before the Court have opened or strengthened offices in Ireland, France and Germany. For a proprietor, the question arises earlier than expected: representation cannot be improvised on the day theinfringement action is brought.

The address for service, the mirror lock in the United Kingdom

Since 1 January 2021, the UK Intellectual Property Office has required an address for service in the United Kingdom, Gibraltar or the Channel Islands, the Isle of Man also being accepted. A European patent designating the United Kingdom is entered on the UK register automatically, but any change of representative requires a Form 51. An address left in the European Economic Area exposes the proprietor to a procedural default in proceedings it will not have seen coming.

The opt-out, the last lever

Article 83 of the Agreement opens a transitional period of seven years from its entry into force on 1 June 2023, during which actions for infringement and for revocation of a European patent may still be brought before national courts. The proprietor may also remove its patent from the exclusive competence of the Court by a declaration ofopt-out, at the latest one month before that period expires. The effect is acquired on entry in the register and the declaration may be withdrawn later. The Administrative Committee may extend the period by a further seven years.

Two limits frame this lever. The unitary patent cannot be opted out, by construction. And the withdrawal of an opt-out is decided once only: it is no longer available once a national action has been brought on the patent.

For a British proprietor, the choice is not ideological. It balances the reach of a single decision across the continent against the risk of a single revocation over the same territory. That calculation is made family by family, according to the strength of the patent and the exposure of the market, not as a matter of principle across the whole portfolio.

What this changes in practice

Three decisions deserve to be taken before any litigation. Map the portfolio, distinguishing unitary patents, European patents validated nationally and patents that have been opted out, because these categories are not defended before the same judges. Check the addresses for service in the United Kingdom and the chain of representation on the continent, two points that are settled in a few days when anticipated and that cost a set of proceedings when they are not. Finally, document the opt-out choice at the level of each family, together with the date on which it will have to be reconsidered.

Brexit did not deprive the United Kingdom of its legal weight. It placed it beside the system, at the very moment that system became the place where European patent law is stated. For proprietors, this does not amount to a loss of rights, but to one further demand of method.

Our firm advises on these choices, before the UPC as before the French courts, in particular as correspondent in France for patents and the UPC. On the interplay between the Court and national judges, see also our analysis of the transitional period and that of the coherence between the unitary patent and national patents. Contact us.

This article is an updated adaptation of two analyses by Matthieu Dhenne first published on Kluwer Patent Blog, on 11 June 2025, UPC After Brexit: The United Kingdom's Salty Sea Voyage, and on 13 June 2025, Licence to File: Brexit, Opt-Outs and European Patent Validation for British Holders. Official sources: Agreement on a Unified Patent Court, Articles 48 and 83; UK Intellectual Property Office, address for service from 1 January 2021.