Rent can be indexed annually during the lease
Yes, the landlord can index the rent once per year, on the anniversary of the lease entry into force. The indexation is based on the health index and is a legal right for primary residence leases — no specific clause is required. The landlord must request it in writing and it takes effect from the month following the request. It is not retroactive.
Rent indexation is the primary mechanism for adjusting rent during a residential lease in Belgium. It is designed to compensate for inflation while maintaining a predictable framework for both parties. The health index (which excludes tobacco, alcohol, and fuel from the consumer price index) is used to ensure a moderate adjustment.
The indexation formula is: Indexed rent = Base rent x (New health index / Base health index)
Where the base health index is the index of the month preceding the lease entry into force, and the new health index is the index of the month preceding the anniversary date.
How to index rent during the lease
| Step | Action |
|---|---|
| 1 | Identify the lease anniversary date |
| 2 | Find the base health index (month before lease start) |
| 3 | Find the current health index (month before anniversary) |
| 4 | Apply the formula |
| 5 | Notify the tenant in writing |
| 6 | Apply the new rent from the following month |
Example: Lease starting 1 June 2024, base rent 850 EUR, base health index (May 2024): 130.50, new health index (May 2025): 134.20.
Indexed rent = 850 x (134.20 / 130.50) = 874.09 EUR/month
The landlord sends a written notification to the tenant, and the indexed rent applies from July 2025 (the month following the request).
Use the official indexation calculator on Statbel to verify your calculation. Always keep a copy of the written notification. An email is generally accepted as valid notification for indexation (unlike for termination notices).
Limits and exceptions to indexation
Several situations can limit or prevent indexation:
- Contractual waiver — if the lease explicitly waives indexation, the landlord cannot claim it
- Energy performance restrictions — regions have introduced indexation limits for properties with poor energy performance certificates
- Late request — indexation cannot be claimed retroactively for past periods not claimed
- Maximum one year of retroactivity — some courts allow claiming the current year’s indexation retroactively, but not prior years
- Rent reduction in effect — if the justice of the peace has ordered a rent reduction, indexation applies to the reduced amount
Indexation can also result in a rent decrease if the health index drops (deflation). In this rare scenario, the tenant could request a downward adjustment.
Regional specifics
Brussels-Capital Region
The ordinance of 27 July 2017 governs indexation in Brussels. Brussels has introduced energy-related indexation restrictions: properties with poor energy performance (E, F, or G certificate) face limited or frozen indexation.
Walloon Region
The decree of 15 March 2018 provides similar rules. Wallonia has adopted comparable energy-related indexation restrictions for the worst-performing properties.
Flemish Region
The Vlaams Woninghuurdecreet of 9 November 2018 regulates indexation in Flanders. Properties with EPC labels E or F face indexation limitations. Flanders has been the most restrictive region on this point.
Regional housing legislation (Brussels ordinance 2017, Walloon decree 2018, Flemish decree 2018) establishing the legal right to annual rent indexation based on the health index. Energy performance-related restrictions vary by region.