Illustration generated for this guide. It does not represent a property for sale.
Original ComparImmo illustration created for this guide.
Cadastral income is not your annual tax bill
A Brussels property listing gives cadastral income of a few hundred euros. Should you set aside that amount each year for the property? The listing alone cannot answer that question. Cadastral income, often shown as RC in French or KI in Dutch, is a tax reference. Annual property tax requires a separate document when you prepare your purchase budget. According to the FPS Finance, cadastral income represents a theoretical average annual net rental income at 1975 levels. Owners can find the non-indexed figure for their own properties in MyMinfin. It therefore does not tell you an apartment’s current rent. Keep two separate entries in your viewing notes: the cadastral figure and the latest documented annual property tax. If the second is missing, write « to obtain » rather than copying cadastral income into your tax budget.
In Brussels, check the year and municipality
Brussels Fiscality explains that property tax is based on indexed cadastral income, with regional, agglomeration and municipal components. Both municipality and year matter. The legal taxpayer is determined by the rights held on 1 January of the tax year. This guide concerns the Brussels-Capital Region. A property in Flanders or Wallonia needs a check with the relevant administration. When comparing two properties, request documents for the same year. An old bill and a recent figure do not give you a consistent basis. Write the tax year beside the amount and distinguish it from the date you receive a copy. If you are preparing a purchase for a subsequent year, treat the available bill as a historical reference. Ask what still needs confirmation before you rely on it for your future budget.
Ask for documents that explain the amount
Request the latest property tax assessment notice from the seller or their representative, together with the identification of the property covered. Check that the address, unit and ancillary spaces match what you are buying. An apartment sold with a garage may require several documents to be read together. A screenshot of the final amount is less useful than a document showing what the charge covers. To read a property file, start with a short record: identified property, year, stated gross amount, listed reductions, final amount and supporting document. Keep a source for every entry. You can ask for unnecessary personal information to be redacted while leaving the details needed for comparison visible. If the seller gives only a verbal estimate, mark it as provisional. The absence of a bill establishes neither that no tax applies nor that the expense will be negligible.
A seller’s reduction is not a promise about your bill
The Brussels Fiscality page describes reductions subject to conditions. For your own budget, ask whether the amount provided includes any reduction and which conditions relate to your circumstances. Do not simply assume that the seller’s bill will become your bill. Resolve this point before setting your first purchase budget. Separate established information about the property from matters depending on your personal situation. If an answer remains unclear, ask the administration about the applicable conditions and discuss with the notary how the issue should be handled in your purchase. A reassuring sentence in a listing is no substitute for that check. You may retain a cautious working assumption in your comparison, provided you label it as an assumption rather than a confirmed amount.
Convert an annual expense into a planning reserve
Fictional example, without a tax calculation: two comparable documents show annual amounts of €1,200 and €1,800. The difference is €600 a year, equivalent to €50 a month if you decide to set money aside for this expense. Dividing by twelve helps organise cash flow. It does not change the payment schedule or establish that the amounts will stay the same next year. To compare several properties, apply the same convention in every column. Show the annual amount and, if useful, its monthly saving equivalent. Keep mortgage repayments, insurance and other identified expenses separate. A lower purchase price can come with a different recurring cost. Your result remains incomplete while an important item is missing. A box marked « to confirm » is more useful than a precise total built on an unsupported assumption.
Market value needs its own evidence
Higher cadastral income does not, by itself, establish that a property will sell more successfully later. A price decision needs its own evidence: condition, location, comparable floor areas and anticipated work. Keep a tax reference separate from a sale valuation or a target rental return. Proprioo’s guide to property prices and Statbel figures explains this other reading. Market indicators belong to a reference period and cannot independently establish the appropriate price of an individual listing. The guide complements your research without calculating property tax. You can then keep two clear questions within the same file: whether the asking price makes sense and whether the ongoing ownership expenses are documented. Answering one does not remove the need to investigate the other.
Use your analysis to identify the questions still open
In ComparImmo, a PDF with readable text can help prepare a structured summary of the file. Ask, for example: « Which amount is cadastral income, and which represents annual property tax? » Then ask which year is stated and what supporting information is missing. Check each answer against the original document. A summary does not confirm eligibility for a reduction and does not issue a tax decision. When buying an apartment in co-ownership, examine shared expenses and common works using their own supporting documents. Keep them distinct from property tax. Before an offer, have the outstanding entries in your record completed. The practical aim is to explain where each amount comes from, what has been confirmed and what still needs checking.
Sources and references
ComparImmo editorial team. Sources checked on 5 October 2026. Check the rules for the region and your circumstances before making a commitment.