The European Commission has decided to create an EU-wide biometric residence document for all British nationals living in the bloc by the end of the post-Brexit transition period

The European Commission has said it wants to ensure British residents in the EU have a “simple, uniform” physical document that helps them prove their residence status and continue to be able to exercise their rights.

This EU-wide document will be issued by the member state in which the applicant resides and will be used only after December 31, when the Brexit transition period is scheduled to end. The details of the plan have recently been laid out in a so-called implementing decision.

“Protecting the rights of EU and U.K. citizens has been one of our main priorities since the beginning of the negotiations with the U.K.,” the Commission said.

The document could be requested by the approximately 1.2 million British people who currently live in the EU and any other Briton moving to the bloc this year.

Under the terms of the Withdrawal Agreement, it is up to each EU country to decide whether to require U.K. nationals apply and obtain a document proving their residence rights under the Brexit deal.

Some EU countries have already indicated that they will apply a mandatory registration system, whereas others will automatically declare all eligible U.K nationals as residents. Brits in the latter group of countries are entitled to request a document proving their status.

The EU-wide residence document will have the same format in all member states and will look like residence permits for other third-country nationals. The only difference would be an “Article 50” mention and an indication of whether it was issued under a declaratory or a registration system.