As part of our pro bono support to “Brexit and the Belgian Brits” (BABBs) community group, we have addressed a formal request to the Belgian authorities – as well as the European Commission – to draw attention to a serious but fixable administrative gap affecting British citizens living in Belgium.

The context: rights that should last a lifetime

Under the Brexit Withdrawal Agreement, British citizens who were already lawfully resident in Belgium before 31 December 2020 retain a comprehensive set of rights, including the right to live and work in Belgium, the right to equal treatment, family reunification rights, and the right to return after periods of absence. These are not temporary concessions – they are permanent, Treaty-level protections.

The Belgian M card is the document that currently attests to this status. For most holders, it works perfectly well. The problem arises when the M card holder’s life moves on, such as when they acquire Belgian nationality or when they obtain a second, complementary immigration status, such as EU long-term residence status or residence as the family member of an EU citizen.

Acquiring Belgian citizenship or an additional residence status should not erase the very rights the Withdrawal Agreement was designed to protect.

The problems we have identified

1. Belgium does not allow holding two residence cards simultaneously

When a beneficiary of the Withdrawal Agreement qualifies for and obtains an additional immigration status (for example, an “F card” as the family member of an EU citizen, or an “L card” as a long-term resident), the Belgian authorities currently require them to surrender their “M card”. However, the European Commission has explicitly confirmed in its guidance that holding multiple immigration statuses also entails the possibility of holding multiple residence documents. Belgian practice is therefore out of step with EU law on this point.

2. British citizens who acquire Belgian nationality must give up their M card

Belgian law treats a person who acquires Belgian nationality as, first and foremost, Belgian. This is uncontroversial. What is problematic is that, once they hand in their M card, there is currently no failsafe mechanism on the Belgian population register to record that this person also holds Withdrawal Agreement beneficiary status. The Court of Justice of the EU confirmed in its Lounes judgment (Case C-165/16) that acquiring the nationality of a host state does not extinguish EU free movement rights. The same principle applies to citizens’ rights under the Withdrawal Agreement and yet the Belgian system currently provides no secure and long-lasting way to record or demonstrate this.

3. The Population Register has no clear codes confirming the Status of Withdrawal Agreement beneficiarY

The M card is currently the only document that proves Withdrawal Agreement beneficiary status in dealings with federal, regional, and municipal authorities. The Belgian national register‘s existing information type system (so-called IT/TI codes) does not include a specific code that records whether a person holds permanent or temporary residence rights under the Withdrawal Agreement, independently of their current nationality or any additional immigration status. Once the M card is gone, that proof often disappears with it.

The solutions we have proposed

Rather than simply raising the problem, our letter sets out concrete, technically feasible proposals that can work within Belgium’s existing population register infrastructure. These require no change to legislation and no new systems need to be built. The solutions require updated instructions and targeted additions to existing coding frameworks.

Solution 1 — Recording dual nationality without restriction

The Belgian Population Register already has a code for dual nationality (IT/TI code 032). However, its current instructions limit its use to persons who voluntarily acquire an additional nationality on top of Belgian nationality and only from 2008 onwards. We propose that this code be applied universally: for anyone who holds Belgian nationality alongside another nationality, regardless of when or how either was acquired. This would allow British-Belgian dual nationals to have both their nationalities properly recorded, making their status visible to Belgian authorities at all levels.

Solution 2 — A dedicated register code for Withdrawal Agreement status

The Register already allows the recording of special information about non-Belgian nationals (IT/TI code 202). We propose the creation of a new sub-category — code 5.3.0 — specifically for British nationals who are Withdrawal Agreement beneficiaries. This new heading would carry four sub-codes distinguishing between temporary and permanent residence rights, and between principal beneficiaries and family members. With this in place, a person’s Withdrawal Agreement status would be permanently recorded on the register, surviving any change of nationality or the acquisition of a different residence status.

What this means for British citizens in Belgium

If you are a British national living in Belgium and you are considering applying for Belgian nationality, or you believe you may qualify for EU long-term resident status or another immigration status, you should be aware of these issues before you take action. Surrendering your M card without a proper record of your Withdrawal Agreement status being preserved elsewhere may result in practical difficulties in proving your rights to Belgian authorities in the future.

We are actively engaging with the Belgian authorities on this and will publish any developments on this page. We believe the proposed solutions are straightforward to implement and we are cautiously optimistic that the authorities will act on them.

In the meantime, if you are considering a change to your residence status or applying for Belgian nationality, we would be happy to advise you on the implications that your plans may have on your current and what action you can take to safeguard your status even without these technical changes taking place.

This article is for general information only and does not constitute legal advice. Published May 2026.