Commercial lease indexation differs from residential
No, commercial lease indexation does not follow the same rules as residential lease indexation. Key differences: it requires an express clause in the lease, uses the consumer price index (not the health index), and the landlord must actively claim it. Without an indexation clause, no indexation is possible for a commercial lease.
Residential lease indexation is governed by regional housing legislation, which makes it quasi-automatic. Commercial lease indexation is governed by the Law of 30 April 1951, supplemented by general contract law. The approach is fundamentally different: residential indexation is a legal right, while commercial indexation is a contractual option.
This distinction reflects the different policy objectives: residential tenants need protection against unexpected rent increases, while commercial parties are presumed to negotiate on equal terms.
Residential vs commercial indexation compared
| Feature | Residential lease | Commercial lease |
|---|---|---|
| Legal basis | Regional housing decrees | Law of 30 April 1951 + contract |
| Clause required | No (automatic right) | Yes (express clause mandatory) |
| Applicable index | Health index | Consumer price index |
| Timing | Anniversary of lease entry | Anniversary of lease entry |
| Must be claimed | Yes (not retroactive) | Yes (not retroactive) |
| Cap or freeze possible | Yes (regional measures) | No (contractual freedom) |
| Frequency | Annual | Annual (or as agreed) |
When drafting a commercial lease, always include an explicit indexation clause specifying the reference index, the base year and month, and the calculation method. Without this clause, the landlord cannot index the rent, even after years of unchanged rent.
How to calculate commercial lease indexation
The formula for commercial lease indexation is:
New rent = Base rent x (New index / Base index)
Where:
- Base rent is the rent agreed at the start of the lease (or at the last revision)
- New index is the consumer price index of the month preceding the anniversary
- Base index is the consumer price index of the month preceding the start of the lease
Unlike residential leases, which use the health index (which excludes tobacco, alcohol, and fuel), commercial leases use the broader consumer price index. This can result in slightly different indexation amounts.
The landlord must claim the indexation in writing. It cannot be applied retroactively beyond the current rental period. If the landlord forgets to claim indexation for a year, that year’s increase is lost.
Regional specifics
Brussels-Capital Region
Commercial lease law is federal and applies uniformly across Belgium. The Law of 30 April 1951 governs commercial leases in Brussels just as in the other regions. Brussels has not adopted specific regional rules for commercial lease indexation.
Walloon Region
The same federal law applies in Wallonia. Commercial lease indexation in Wallonia follows the identical rules as in the other regions. Any temporary indexation freezes imposed for residential leases do not apply to commercial leases.
Flemish Region
Federal commercial lease law applies equally in Flanders. The Flemish residential lease decree (Woninghuurdecreet) does not apply to commercial leases. Any Flemish measures limiting residential rent indexation have no effect on commercial leases.
Law of 30 April 1951 on commercial leases — Text on Justel. Law of 2 August 1966 (indexation mechanism). Commercial lease indexation is a federal matter.