Key Constitutional Court ruling on wealth tax: What non-profits need to know

In a decision delivered on December 4, 2025, the Belgian Constitutional Court annulled a provision of the Law of December 28, 2023, containing various tax provisions relating to the ‘tax to reimburse inheritance tax’, also known as the ‘wealth tax’.

I.          What is the “wealth tax”?

The tax to reimburse inheritance tax’ (‘taxe compensatoire des droits de succession’ in French and ‘taks tot vergoeding der successierechten’ in Dutch), commonly referred to as the ‘wealth tax’, is an annual tax due by non-profit organisations such as (international) non-profit associations and private foundations (hereafter: “NPOs”).

The Law of December 28, 2023, containing various tax provisions (hereafter: “Law”) increased the applicable wealth tax rate as from January 1st, 2024. The previously single rate of 0.17% was replaced by a progressive ascending rate, now ranging from 0% to 0.45%, depending on the value of the NPO’s eligible taxable assets.

This rate increase of the wealth tax was accompanied by a list of exceptions. NPOs active in several sectors now fall outside the scope or are neutralised (meaning they continue to pay a maximum of only 0.17% in taxes), provided certain conditions are met.

II.         The Constitutional Court’s decision of December 4, 2025 

A. Challenge to the Law

Several NPOs challenged the list of exceptions introduced by the Law before the Constitutional Court, arguing that the new rules infringe Articles 10 and 11 of the Constitution, which guarantee equality and prohibit discrimination. Specifically, the NPOs claimed that the Law created an unfair difference between two types of organisations:

• Those that pay the wealth tax but can obtain a partial exemption (e.g., NPOs managing private archives); and
• Those that pay the same tax but cannot obtain any exemption (e.g., NPOs running or linked to libraries).

The tax increase introduced by the Law was effectively cancelled for the first group, while the second group was left to bear the full increase. In short, library-related NPOs were treated less favourably than those involved with private archives.

B. The Court’s reasoning

The Constitutional Court ruled in favour of the NPOs on this key point. The Court reiterated that the principle of equality and non-discrimination does allow for differences in treatment between categories of persons/entities, provided these differences are based on an objective criterion and are reasonably justified. Whether such justification exists depends on the purpose and effects of the measure, as well as the nature of the principles involved. The principle is breached when there is no reasonable balance between the means used and the aim pursued.

However, the Court found that limiting the advantage to the taxpayers listed in the Law was not reasonably justified, as these taxpayers were not meaningfully different from other comparable taxpayers.

C. Outcome and transitional measure

As a result, the Constitutional Court annulled this provision of the Law. However, to avoid several categories of taxpayers facing an unexpected tax burden with retroactive effect, and to give the Federal Parliament time to adopt new legislation, the effects of the annulled provision will remain in place until December 31, 2026, at the latest.

III.        Conclusion: implications and ongoing developments

While the effects of the annulled provision will remain in place until December 31, 2026, giving the Federal Parliament time to introduce new legislation, NPOs affected by the wealth tax should closely monitor further legislative developments, as changes to the tax regime are expected in the coming year.

Moreover, other annulment proceedings appear to be still pending before the Court, making it even more important for NPOs to stay informed about future developments in this area. EY Law will continue to monitor these developments and keep you informed to prepare NPOs for any changes.