Belgium’s Richest Families Hold €85.5 Billion in Luxembourg

A new investigation by Belgian financial newspapers De Tijd and Le Soir has revealed that Belgium’s 50 wealthiest families collectively manage €85.5 billion through Luxembourg-based companies — a sum exceeding the Grand Duchy’s entire annual economic output. The findings, based on more than 32,000 records from Luxembourg’s register of ultimate beneficial owners (UBO), shed light on the scale of offshore wealth held by Belgian elites and have reignited debates about tax fairness and the two-speed fiscal system in Belgium.

The Scale of Wealth in Luxembourg

According to the investigation, published on June 20, 2026, Belgium’s 100 richest families collectively control 416 Luxembourg-registered companies valued at over €91 billion. The concentration is extreme: the top 50 families alone account for €85.5 billion, meaning the next 50 families collectively hold just €5.5 billion. The Brussels Times reports that 64 of the 100 wealthiest families — nearly two-thirds — are beneficiaries of companies registered in the Grand Duchy.

Among the top 50, 42 families use financial structures in Luxembourg. In total, approximately 9,800 Belgian nationals control or co-control about 11,200 Luxembourg-registered companies, making Belgians the third-largest nationality in Luxembourg’s commercial register, after the French and Luxembourgers themselves.

The ‘Letterbox’ Company Phenomenon

A striking feature of the investigation is the prevalence of so-called “letterbox” companies. At least 307 of the Belgian-controlled entities have no employees and no physical office in Luxembourg — pure mailbox structures. P-Magazine reports that 52 of the wealthiest families use such structures, holding approximately €54 billion. When journalists visited the registered addresses, they found tax advisory firms, trust offices, and administrative service providers where thousands of companies share the same address.

These structures are used to hold investments, cash, real estate, luxury goods, and shares in Belgian and foreign businesses. While the practices are generally legal — using SOPARFI (Société de Participations Financières) holding structures — the scale has drawn sharp criticism.

The Marc Coucke Example

The investigation highlights the case of prominent Belgian entrepreneur Marc Coucke, founder of Omega Pharma. In 2018, Coucke publicly declared he had “nothing in Luxembourg” on principle. Yet the UBO register reveals he registered four holding companies in Luxembourg between 2022 and 2025, collectively holding over €130 million. Bloom Law notes that Coucke’s case illustrates how even those who publicly distance themselves from Luxembourg ultimately use such structures when the amounts become large enough.

Expert Analysis: Legal but Under Scrutiny

Denis-Emmanuel Philippe, a tax lawyer at Bloom Law and lecturer at ULiège, was interviewed by De Tijd on the matter. “My experience, however, is that the Belgian tax authorities in 2026 are often no longer satisfied with a Soparfi that only rents an office in Luxembourg and holds a few meetings a year,” Philippe said. “They are increasingly looking at the economic ‘substance’ of Luxembourg holdings: do they also carry out an economic activity? Passive holdings in the Grand Duchy are therefore under heavy fire due to the strict anti-abuse provisions in our country.”

Philippe also noted that dismantling Luxembourg structures carries heavy fiscal consequences for Belgian shareholders, creating a “lock-in” effect that perpetuates the status quo. Families also fear that Belgian banks, in the fight against money laundering, will ask difficult questions about the origin of assets held in Luxembourg for decades.

A Two-Speed Tax System?

The investigation has reignited a broader debate about tax fairness in Belgium. Business AM notes that the findings come against a backdrop of increasing wealth concentration globally, with the number of ultra-high-net-worth individuals (those with over €26 million) growing by 26% in Europe over the past five years.

In Belgium, the timing is particularly sensitive. The government recently doubled the annual tax on securities accounts from 0.15% to 0.3%, effective early 2026. Meanwhile, the Flemish socialist party Vooruit — part of Prime Minister De Wever’s five-party federal coalition — has been pressing for a “millionaire’s tax,” an annual progressive contribution on total assets above €1 million that could raise €1 billion annually.

As P-Magazine editorialized: “Belgians increasingly feel that there are two tax speeds. One for those who receive a pay slip, fill out a tax return and hope not to make a mistake. And one for those who can surround themselves with tax specialists, lawyers, asset managers and international structures.”

Why Luxembourg?

Luxembourg’s appeal for wealth management is well-established. Financial journalist Ludwig Verduyn, cited in De Morgen, notes that Luxembourg offers something many entrepreneurs find difficult to find in Belgium: predictability. The Grand Duchy provides political and fiscal stability, geographic proximity (approximately 200 km from Brussels), a dense network of law firms and corporate service providers, and SOPARFI structures that can receive dividends and capital gains from qualifying participations tax-free.

The figure of €91 billion represents a near-doubling from the €48 billion reported by the same newspapers in 2018, despite tax reforms, data leaks (LuxLeaks, OpenLux), and increased transparency requirements.

What’s Next?

The investigation raises fundamental questions about whether political action will follow. The proposed millionaire’s tax remains a contentious issue within the coalition government. Luxembourg authorities, for their part, reject the tax haven label, pointing to tightened substance requirements, EU transparency directives, and automatic information exchange agreements.

For the wealthy families themselves, the path forward is complicated. As Philippe noted, liquidating Luxembourg structures carries significant tax consequences, and explaining decades-old assets to Belgian banks under anti-money laundering rules presents its own challenges. The status quo, it seems, is remarkably sticky — even as public scrutiny intensifies.