Rent indexation is the yearly adjustment of rent to the cost of living, calculated on the official Belgian health index published by Statbel. As a landlord you can generally index once a year, around the anniversary of the lease, provided the lease is written and registered.
What is the health index?
The health index is derived from the consumer price index, excluding products such as alcohol, tobacco and fuels. Statbel publishes it monthly. Belgian rent indexation always uses the health index, not the regular consumer price index.
When can you index?
You can index at the earliest on the anniversary of the lease taking effect, and at most once a year. Retroactive indexation is often possible but usually limited to the last three months, so a missed indexation cannot be recovered indefinitely.
Differences by region
Rent is a regional matter, so rules differ between Flanders, Brussels and Wallonia. In Flanders the allowed indexation can depend on the property’s EPC label. Brussels and Wallonia have their own conditions and have applied temporary measures in the past. Always check the current rule for the region where your property is located.
The formula
New rent = base rent × (new health index ÷ base health index)
The base index is the health index of the month before the lease started (depending on the base year). The new index is the one for the month before the anniversary. The base year (e.g. 2013 = 100 or 2004 = 100) determines which index series you use.
How to calculate it, step by step
- 1
Take the base rent
The rent as set at the start of the lease.
- 2
Find the base index
The health index of the month before the lease started, in the correct base year.
- 3
Find the new index
The health index of the month before the lease anniversary.
- 4
Apply the formula
New rent = base rent × new index ÷ base index. Round according to the usual rules.
Frequently asked questions about rent indexation
Can I index every year?
Yes, generally once a year, at the earliest on the anniversary of the lease taking effect, provided the lease is written and registered.
Which index should I use?
Always the health index (not the regular consumer price index), as published monthly by Statbel.
Does the EPC label matter?
In Flanders the EPC label can affect the allowed indexation. Rules differ per region and can change, so check the current regulation.
Can I index retroactively?
Often yes, but usually limited to the last three months, so a missed indexation cannot be corrected indefinitely.
This guide is a general explanation, not legal advice. Rent rules are regional and change regularly. Cynsio computes the exact indexed rent, accounting for region and EPC.