Several types of clauses are prohibited by law
Belgian law prohibits clauses in residential leases that waive the tenant’s mandatory rights, impose a notice period exceeding 3 months, include disproportionate penalties, or apply unlawful indexation. These prohibitions are a matter of public order: the judge can annul them on their own initiative, even if neither party raises the issue.
The prohibition of certain clauses aims to protect tenants from unfair contract terms. The Belgian Code of Economic Law (Book VI) provides a general framework against abusive clauses, while regional housing legislation adds specific prohibitions for residential leases.
A prohibited clause is null and void from the outset. The rest of the lease remains valid and enforceable.
Common prohibited clauses
| Prohibited clause | Why it is illegal |
|---|---|
| Waiver of tenant’s mandatory rights | Cannot contract out of protective legislation |
| Notice period exceeding 3 months for tenant | Law caps it at 3 months |
| Automatic termination for late payment | Must go through court |
| Blanket prohibition of all pets | Considered disproportionate |
| Disproportionate penalty clause | Must be proportionate to actual damage |
| Indexation not based on health index | Only legal indexation formula permitted |
| Obligation to take insurance from a specific provider | Restricts freedom of choice |
| Waiver of right to go to court | Fundamental right |
| Clause making registration costs payable by tenant | Registration is the landlord’s obligation |
| Discriminatory clauses | Prohibited under anti-discrimination law |
Additional examples specific to residential leases:
- Clause prohibiting the tenant from joining a tenants’ association
- Clause requiring the tenant to leave during repairs (beyond what is reasonable)
- Clause imposing maintenance obligations that exceed what the law requires of a tenant
BailBelgique generates leases that automatically exclude all prohibited clauses and comply with the mandatory provisions of each region.
What to do if you find a prohibited clause
If your lease contains a prohibited clause:
- Notify the landlord in writing, explaining that the clause is prohibited by law
- The clause is already null by operation of law — you do not need a court order for it to be unenforceable
- If the landlord insists on enforcing the clause, you can file a complaint with the justice of the peace
- The judge will confirm the nullity and the clause will be struck from the lease
You do not need to challenge the entire lease. Only the abusive or prohibited clause is annulled; all other provisions remain in force.
Regional specifics
Brussels-Capital Region
The Brussels ordinance of 27 July 2017 contains a detailed list of mandatory provisions that cannot be derogated from. Clauses that contradict these provisions are automatically null.
Walloon Region
The Walloon decree of 15 March 2018 specifies mandatory provisions and has been interpreted strictly by courts. Wallonia also imposes transparency obligations regarding rent composition.
Flemish Region
The Flemish Housing Rental Decree of 9 November 2018 provides the most detailed framework, with explicit lists of permitted and prohibited clauses. The mandatory lease template helps prevent the inclusion of prohibited clauses.
Belgian Code of Economic Law, Book VI + Regional housing legislation — Prohibited clauses are null and void by operation of law.