Cadastral income in Uccle

Revenue cadastral is calculated as the estimated annual rental income on 1st January 1975 minus 40%, and then indexed for inflation to the present day.

Unless you have had your house extended or modified, or possibly revalued, then the revenue cadastral has nothing to do with house prices or rental values today. It is based on valuations made 43 years ago.

There is an effort to revalue properties, but as you can imagine, they are in no rush, because rich people live in expensive houses, and the Belgian government prefers to tax poor people.