Taboo Falls: More Belgian Cities Review Cadastral Income Values
A growing number of Belgian cities and municipalities are breaking a long-standing political taboo by reviewing and updating their cadastral income (kadastraal inkomen) values — the fictional rental values assigned to properties that have not been systematically updated since 1975. The trend, which now includes cities such as Leuven, Willebroek, Mol, Sint-Katelijne-Waver, and Sint-Agatha-Berchem, could have significant implications for property taxation across the country.
What Is Cadastral Income?
Cadastral income (KI) is a theoretical annual net rental value assigned to every property in Belgium by the tax administration. It serves as the basis for calculating several taxes, most notably the onroerende voorheffing (property tax), which represents approximately 60% of municipal fiscal revenue. Municipalities receive over 70% of property tax revenue, making it one of the few significant tax levers they control locally, as Batibouw reported.
The values currently in use were established in 1975 and have never been systematically updated through a general revaluation. While KI is indexed annually for inflation — by 2.5% in 2026 — the base values remain frozen at 1975 levels. This has created significant horizontal inequity: two identical homes can pay vastly different property taxes depending on whether renovations were properly registered.
Leuven Leads the Way
On May 18, 2026, the city of Leuven announced plans to review the cadastral income of thousands of homes. According to VRT NWS, the city will identify properties where renovations — such as extensions, extra bathrooms, or improved sanitation — were not registered with the cadaster.
Schepen van Financiën Thomas Van Oppens (Groen) stated: “It’s about fiscal justice. It cannot be that there are two similar homes where one is correctly registered in the cadaster and pays the correct property tax, while the other pays only a few dozen euros. That cannot be.” The city has allocated €326,000 over three years for the operation and expects €2.05 million in additional revenue from municipal surcharges by 2031, as Leuven Actueel reported.
Van Oppens reassured residents that most would not be affected: “About 10% of all homes raise questions for us. Because the cadaster shows, for example, that they supposedly do not have central heating or sanitary facilities. That seems unlikely to us.” Letters will be sent to affected homeowners in the second half of 2026.
A Growing Trend
Leuven is not alone. In January 2026, Sint-Agatha-Berchem in the Brussels-Capital Region sent letters to residents asking them to confirm whether their homes have heating and/or a bathroom. The municipality stated on its official website that many properties are still registered in very low comfort categories that no longer reflect reality, adding: “The goal is simply that everyone pays a tax corresponding to the actual value of their home.”
Municipalities including Mol and Sint-Katelijne-Waver have also announced plans to update cadastral income values. The trend follows earlier precedents: in April 2020, four Hageland municipalities — Zoutleeuw, Geetbets, Kortenaken, and Linter — began investigating whether KI values for certain homes still reflected actual comfort levels, as VRT NWS reported at the time.
Why Now?
Several factors are driving the sudden wave of KI reviews. Belgian municipalities face rising structural costs in areas such as pensions, personnel, social services, and police zones. Meanwhile, the federal reform of personal income tax — gradually raising the tax-free threshold from €10,910 in 2025 to €15,300 by 2029 — is expected to cost Walloon municipalities alone €95–135 million annually by 2030, according to Batibouw.
Property tax remains one of the few revenue levers that municipalities can adjust locally. In 2026, 86 out of 565 Belgian municipalities increased their property tax surcharges, compared to just 16 in 2025 — a more than fivefold increase.
Political Pushback
The reviews have not been without controversy. Opposition parties in Leuven have described the initiative as a “hidden tax increase.” Britt Huybrechts of Vlaams Belang warned that higher property taxes on landlords would likely be passed through to tenants via higher rents, worsening affordability in an already tight housing market. Zeger Debyser of N-VA proposed using additional revenues to lower municipal surcharge rates, arguing the city should avoid creating “a profit model.”
Privacy concerns have also been raised. The use of data from permit applications, subsidy requests, and other administrative databases to identify “suspicious” properties has drawn criticism from opposition figures who question the boundary between service delivery and fiscal surveillance.
What to Watch
The municipal-level actions raise the question of whether they will eventually force a nationwide revaluation — something the federal government has long avoided. Legal challenges from property owners contesting revaluations are also likely. For homebuyers, municipal fiscal policy is becoming an increasingly strategic factor in purchasing decisions, as local tax burdens vary significantly between neighboring municipalities.
The inter-municipal association IGO is set to begin assessment work in Leuven in mid-August 2026 under a three-year contract. The results of this operation could serve as a template for other municipalities considering similar reviews.