Indexation is a right, not an obligation
No, rent indexation is not mandatory. It is a right of the landlord that can be exercised or waived. The lease can even exclude indexation entirely through an explicit clause. If the landlord chooses not to index, the rent stays at the initial or last indexed amount.
The legal framework is clear:
- Article 1728bis uses the wording “can be requested” — a facultative right
- The landlord may choose not to index in any given year
- The lease may include a clause waiving the right to index
- If indexation is not requested, it does not apply automatically
When might a landlord waive indexation
Some situations where not indexing may be strategic:
- Tenant retention: keeping a good tenant is worth more than a small rent increase
- Below-market rent: if the rent is already well above the indexed amount due to market conditions
- Short-term lease: for leases under 1 year, indexation is often not worth the administrative effort
- Negotiation leverage: waiving indexation in exchange for a lease extension or better property care
Even if you choose not to index this year, you can always resume indexation in future years. The calculation will use the original base rent and the current index, so you do not lose the cumulative effect of inflation.
Financial impact of not indexing
The cost of not exercising the indexation right can be substantial over time:
| Years not indexed | Approximate loss (on 800 EUR base rent) |
|---|---|
| 1 year | ~20 EUR/month |
| 3 years | ~60 EUR/month |
| 5 years | ~100 EUR/month |
| 9 years (full lease) | ~200 EUR/month |
Over a 9-year lease, not indexing at all could represent a total loss of over 10,000 EUR in rental income. However, this must be weighed against tenant stability and relationship quality.
Regional specifics
Brussels-Capital Region
Under the Ordinance of 27 July 2017, indexation remains a right. For properties with poor EPC labels, indexation may be restricted or frozen anyway.
Wallonia
The Decree of 15 March 2018 treats indexation as a right. Similar EPC restrictions apply.
Flanders
The Flemish Housing Rental Decree of 9 November 2018 confirms indexation as a landlord’s right, with EPC restrictions for E and F labels.
Article 1728bis of the Belgian Civil Code — “peut etre demandee” (can be requested), indicating a right rather than an obligation.