The agreement usually takes the form of either an option or an agreement of sale (compromis de vente), i.e. a preliminary contract
In the case of the option, it may be an option to sell. In this event, the owner promises to sell the real estate at a set price (unilateral promise to sell). The owner is bound to this commitment for the term of the option and may not sell to another person. The buyer, for her/his part, is not obliged to buy. In some cases, the seller will ask the buyer to ‘commit’, i.e. to offer a price that the seller may accept or reject.
The agreement can also take the form of an agreement of sale or preliminary contract. However, in reality, as soon as the parties have signed this document, the sale is final; the parties may no longer change their minds. The sale will not take effect against third-party claims until the moment that the authentic instrument is filed with the mortgage records office.
According to federal law, the preliminary contract must contain certain information. Depending on the region where the property is located (Brussels, Flanders, or Wallonia), other additional things must be mentioned in the agreement. For example, in Brussels, information about the town planning permits and certificates, any violations regarding the property that may exist, etc., must be indicated in the preliminary contract. The preliminary contract may also include some conditions precedent or subsequent (e.g. linked to getting a mortgage loan). It is thus a very important document for which legal counsel is necessary before committing oneself.