The compromis is the preliminary sale agreement signed once buyer and seller agree on price and terms. In Wallonia it is legally binding: it fixes the property, the price and the conditions, and commits both sides to complete. The notarial deed then follows within about four months. Source: Notaire.be.
The compromis is often misread as a mere formality before the “real” contract. It is not. In Belgium the compromis (preliminary sale agreement) is itself a binding contract: once both parties sign, the seller is committed to sell and the buyer is committed to buy at the agreed price. The later notarial deed executes that agreement; it does not create it.
What the document actually contains matters, because it sets the rules for everything that follows. It identifies the property and the parties, states the price, records the deposit (commonly around 10%), lists any suspensive conditions such as obtaining a mortgage, and fixes the deadline for the deed, usually about four months. It also references the seller’s documents: the PEB certificate, the electrical compliance certificate, the soil information and the urban-planning extract. Source: Notaire.be.
The counter-intuitive point for buyers coming from other countries: signing the compromis, not the notarial deed, is the decisive step. By the time you reach the notary’s office for the deed, the essential terms are already locked. That is why the conditions you negotiate before the compromis, especially a loan condition, are so important.
Regional note: the mechanism of the compromis is the same across Belgium, but the registration duties that fall due differ by region, 3% for an own and sole home in Wallonia since 1 January 2025, 2% in Flanders, and 12.5% in Brussels with an allowance. Source: Lydian 2025.
At a glance
| Element of the compromis | What it fixes |
|---|---|
| Parties and property | Who buys, who sells, exact property |
| Price and deposit | Agreed price; deposit often around 10% |
| Suspensive conditions | For example, obtaining a mortgage loan |
| Seller documents | PEB, electrical certificate, soil, planning extract |
| Deadline for the deed | Usually about 4 months |
| Legal status | Binding on both parties once signed |