Belgium Property Due Diligence: Legal Checklist for Expat Buyers

The four months between signing the compromis de vente and completing the authentic deed in Belgium are not waiting time. They are the window during which your notary conducts legally mandated due diligence — and during which you should be running your own parallel checks. Foreign buyers who treat this period passively, assuming the notary handles everything, routinely discover after the fact that certain protections required active engagement from their side. Some of these gaps are recoverable. Others are not, once the deed is signed.

The BIS Number: Your Entry Ticket to the Belgian Property System

Before anything else can proceed, non-resident foreign buyers and newly arrived expats who have not yet completed Belgian municipal registration need a BIS number. This is Belgium's administrative identification number for individuals who have a financial or legal relationship with the Belgian state but do not yet reside within its borders.

The BIS number mirrors the standard Belgian National Register Number (Rijksregisternummer / Numéro de Registre National) in structure — eleven digits — but with the month of birth increased by 20 or 40 to signal non-resident status. It is a permanent identifier that does not expire.

The notary handling your purchase will coordinate its acquisition as part of the transaction process, since the number is required to register the authentic deed with the Federal Public Service Finance and to calculate registration duties. You cannot complete a Belgian property purchase without one. Starting this process early avoids administrative delays at the closing stage.

Soil Certificate (Bodemattest)

For properties in Flanders, the Bodemattest (soil certificate) is a mandatory disclosure document issued by the Flemish Public Waste Agency (OVAM). It certifies whether the land associated with the property has been investigated for soil contamination, what the findings were, and whether any remediation obligations remain.

The seller is legally required to obtain and provide the Bodemattest before the compromis can be validly signed in Flanders. A property with known contamination and outstanding remediation orders may still legally be sold, but the obligation to remediate transfers to the new owner. Review the Bodemattest carefully with your notary before proceeding. Properties on former industrial land, garages, dry cleaners, or petrol station sites carry elevated contamination risk.

In Wallonia, the equivalent document is the certificat du sol, and in Brussels, the attestation du sol. The obligations and process differ by region, but the principle — that soil contamination is a buyer's risk requiring pre-purchase disclosure — applies across all three.

Urban Planning Certificate and Building Permit Check

The urban planning certificate (stedenbouwkundige inlichtingen / certificat d'urbanisme) is a document issued by the municipal authority that discloses the property's zoning designation, any outstanding notices of infraction, permitted land use, and any pending urban planning measures that could affect the property or its neighborhood.

The notary will request this certificate as part of standard due diligence, but your independent review matters. Extensions, outbuildings, and alterations added without the required building permit are a structural risk. Unauthorized construction does not transfer liability to the municipality — it transfers to you, the new owner, who becomes responsible for regularizing or demolishing the unauthorized works.

Before making an offer, ask the seller directly whether all structures on the property — including any rear additions, converted garages, basement habitation, or garden rooms — have been built with the required permits and conform to what was authorized. A clear answer on this point, documented in writing, protects you if issues emerge during the notarial period.

Property Survey

Belgium does not mandate a structural survey as a condition of purchase. This distinguishes it from the UK market, where buyers routinely commission independent level 2 or level 3 surveys. In Belgium, the decision to commission an independent structural inspection lies entirely with the buyer.

For expatriate buyers without deep knowledge of Belgian construction standards — particularly older Brussels townhouses, pre-war Flemish row houses, or Walloon rural properties — an independent structural survey by a registered engineer or architect is strongly advisable. Specific concerns in the Belgian market include facade condition on older brick buildings, chimney and hearth integrity, asbestos in pre-1980 construction, and basement moisture ingress common in older Brussels properties with shallow foundations.

The cost of a structural survey typically runs €500 to €1,500 depending on property size and scope. That is an inexpensive form of insurance compared to discovering structural defects after the deed is signed, at which point the Belgian legal standard of caveat emptor largely applies unless deliberate concealment by the seller can be proven.

Property Insurance and Homeowner Insurance

Belgian mortgage lenders require proof of valid property insurance (brandverzekering / assurance incendie) before completing. This is not a legal formality — the bank's collateral security requires the physical asset to be insured.

Belgian homeowner insurance covers fire, water damage, storm damage, and natural disasters as standard. Most policies also include liability coverage for damage caused by your property to third parties. In a co-owned apartment building, the VME's building insurance covers the common parts and structure; your personal policy covers the interior fitting of your unit and your civil liability.

Premium levels vary by insurer, region, and property type. Budget approximately €300–€600 annually for a typical apartment and €600–€1,200 for a house, before adjusting for property value, location, and coverage level. Compare at least three insurers — the Belgian market is competitive and rates vary substantially.

Power of Attorney: Buying from Abroad

Expatriate buyers frequently cannot be physically present in Belgium for the authentic deed signing. Belgian notarial practice has fully accommodated this through the digital power of attorney (procuration numérique / digitale volmacht).

This mechanism allows a foreign buyer to grant power of attorney to a designated clerk within the notary's office via a secure video conference and an advanced electronic signature, typically authenticated through the Belgian eID system or the Itsme mobile application. The clerk then physically signs the authentic deed on the buyer's behalf. The transaction is legally complete and fully valid.

The digital power of attorney process requires advance scheduling and identity verification steps. Begin the conversation with your notary at least two to three weeks before the planned deed signing date to allow the administrative process to be completed correctly. Do not assume this can be arranged at the last minute.

The Breyne Law: Off-Plan Purchases

If you are buying a property that does not yet exist — a new-build apartment sold from a developer's plan or a house under construction — the Breyne Law (Wet Breyne / Loi Breyne) governs the transaction rather than the standard compromis framework.

The Breyne Law provides several specific protections for off-plan buyers. It imposes a mandatory structure on price and payment, linking installments to verified construction progress stages rather than arbitrary developer-imposed deadlines. It requires the developer to provide a financial guarantee covering completion of the works if they default. It limits the deposit payable on signing to a maximum of 5% of the total price.

The Breyne Law also provides a strictly limited seven-day reflection period after signing the off-plan contract. This is the only genuine cooling-off right in Belgian real estate — and it applies only to off-plan developer contracts under the Breyne Law, not to standard second-hand property purchases. The widely circulated belief that a 14-day cooling-off period exists for all Belgian real estate transactions is a dangerous myth with no basis in standard property law.

For a complete treatment of Belgian property due diligence — including regional variations in soil certificate requirements, the full notarial timeline, and a step-by-step checklist for each stage of the purchase process — the Belgium Expat Buying Guide covers what you need to verify before and after each document you sign.

See more Belgium guides →