Belgian Municipalities Take Lead on Cadastral Income Reform

Frustrated by decades of federal inaction, Belgian municipalities are taking matters into their own hands to reform the country’s outdated cadastral income (KI) system — a property tax mechanism based on fictional rental values from 1975. At least four municipalities, including Willebroek, Leuven, Diest, and Scherpenheuvel-Zichem, have begun sending questionnaires to residents to map the actual condition of their homes, aiming to correct outdated data and ensure fair taxation.

What Is Cadastral Income?

The cadastral income is the fictional annual rental value assigned to every property in Belgium, used by the government to calculate taxes such as the “onroerende voorheffing” (property tax) and municipal surcharges known as “opcentiemen.” According to VRT NWS, the system has not been fundamentally updated since 1975, despite a legal requirement for revision every ten years. Since 1992, values have only been adjusted for inflation through annual indexation.

Municipalities Take Action

In Willebroek, Alderman of Finance Luc Spiessens (N-VA / Team Eddy) told VRT NWS that roughly 25% of the municipality’s 11,000 homes reportedly have no bathroom according to official cadastral records — a figure that bears little resemblance to reality. “The system is currently unjust because some people are taxed far too low,” Spiessens said. He added that if the data correction yields substantial additional revenue, the municipality could lower its general surcharge rate, meaning “everyone benefits.”

Leuven is taking a more systematic approach, reviewing approximately 10% of its homes and hiring an appraiser at a cost of €100,000, as VRT NWS reported. Alderman of Finance Thomas Van Oppens (Groen) framed the initiative as a matter of 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 only pays a few dozen euros,” he said.

Residents in Willebroek have largely welcomed the effort. Bart Smedts, whose home the cadaster lists as having no bathroom, told VRT NWS: “According to the cadaster, my home has no bathroom. Before, there was just a hole in a wooden beam, straight into the cesspit. That needs to be corrected, I have no problem with that.”

The Scale of the Problem

The data gap is not new. The Belgian Court of Audit (Rekenhof) documented it as early as 2006, finding that only 59% of homes had central heating according to the cadaster, versus 73% according to the National Institute of Statistics. For bathrooms, the gap was even wider: 77% versus 96%. The financial stakes are enormous — municipal surcharges on property tax account for approximately 47% of total municipal revenues, generating €3.2 billion in 2025, according to P-Magazine.

Political Sensitivity at the Federal Level

Despite the clear need for reform, the federal government has remained paralyzed. Minister of Finance Jan Jambon (N-VA) has declined to comment on the issue. Professor Michel Maus (VUB), a tax law expert, explained the political dynamics to VRT NWS: “The Minister of Finance who gives such an assignment to his administration will be held politically accountable for it.” No federal minister has been willing to tackle the reform, fearing being labeled a “tax increaser.”

Professor Mark Delanote (UGent) echoed this assessment in an earlier VRT NWS interview, noting that the system “is severely outdated and feels unjust to many people.” He added that the government already possesses all the data needed for reform through property transaction records and mandatory rental registrations, but the political will is lacking.

Legal Limitations and Opposition

Municipalities face significant legal constraints. Professor Maus noted that local governments do not have the authority to adjust the cadastral income itself — that power rests solely with the federal Minister of Finance. Municipalities can only rely on the voluntary cooperation of residents through questionnaires. If residents do not respond within 30 days, municipalities can schedule a site visit.

The initiatives have also drawn criticism. In Leuven, opposition council member Britt Huybrechts (Vlaams Belang) warned that the update could penalize homeowners who have invested in renovations, and that costs for rental properties would inevitably be passed on to tenants. “All to fill the city’s coffers,” she said.

What’s Next?

The growing municipal activism is putting pressure on the federal government to act. If enough municipalities update their data, the pressure for a national reform may become irresistible. Experts suggest that a comprehensive overhaul would require coordination across federal, regional, and municipal levels, possibly as part of a broader transfer of property taxation to the regions. For now, local governments are doing what the federal level has avoided for half a century — taking the first steps toward a fairer system.