What is the rent indexation formula?

New rent = Base rent × (New health index ÷ Starting index). The starting index is the one from the month before the lease was signed. The new index is the one from the month before the anniversary date.

When can rent be indexed?

Indexation is possible every year on the anniversary date of the lease coming into effect, provided the contract is written and does not exclude indexation. The request must be made in writing within 3 months of that date.

Can the EPC prevent rent indexation?

Yes. Since 14 October 2023, a poor EPC rating (E, F or G) can limit or prohibit indexation in Wallonia, Flanders and Brussels. The rules vary by region and the applicable calendar.

Can rent be indexed on an unregistered lease?

No. A lease that is not registered with the FPS Finance cannot be indexed until it has been regularised. Registration is free and is the landlord's responsibility.

Is rent indexation the same in Wallonia, Brussels and Flanders?

The calculation formula is the same throughout Belgium. However, specific rules limit indexation based on the property's EPC rating, with a schedule specific to each region since 14 October 2023.

Rent indexation in Belgium: complete guide 2026

Q: What is rent indexation in Belgium?

Rent indexation is an annual adjustment of the rent to the cost of living. It is based on the health index published every month by Statbel. It is not automatic: the landlord must request it in writing from the tenant.

What is rent indexation?

Rent indexation is an annual adjustment of the rent to inflation. It is based on the health index published every month by Statbel. The same principle applies to all primary residence leases in Belgium.

Rent indexation is not automatic. The landlord must request it. Without a written request, the rent remains unchanged. In practice, indexation is a right of the landlord, not an obligation.

Rent indexation in Belgium is governed by the Civil Code and by regional decrees. Each region (Wallonia, Brussels, Flanders) applies its own rules.

Conditions for indexing rent

Several conditions must be met before rent can be indexed:

The lease agreement must be in writing. An oral lease cannot be indexed.
The lease must not exclude indexation (some contracts remove this provision).
A full year must have elapsed since the lease came into effect.
The anniversary date of the lease must be observed.
The landlord must make a written indexation request to the tenant.

The request must be sent within 3 months of the anniversary date. After this deadline, indexation is no longer retroactive.

Rent indexation formula

The indexation formula is set by Belgian law:

New rent = Base rent × (New health index ÷ Starting index)

Base rent: the initial rent set in the lease.
Starting index: health index from the month before the lease was signed.
New health index: index from the month before the anniversary date.

This calculation applies to all primary residence leases in Belgium.

The health index: the reference index

The health index is the index used as the basis for indexation. It is published every month by Statbel (the Belgian statistical office). It excludes certain products such as tobacco, alcohol and fuels.

All official figures are available on the Statbel website. Price indices are updated every month. The consumer price index serves as the basis for the health index and reflects fluctuations in the cost of living in Belgium.

How to index rent step by step

Here is how to index rent in practice, in six steps:

Check the lease: confirm that indexation is not excluded.
Note the anniversary date: this is the anniversary of the date the contract came into effect.
Find the starting index: health index from the month before the lease was signed.
Look up the new health index: the one from the month before the anniversary date.
Apply the formula and calculate the new rent.
Send a written request to the tenant, within 3 months.

To simplify the calculation, use our free indexation calculator.

Rent indexation 2025 and 2026

The 2025 indexation affected several hundred thousand leases in Belgium. The rise in consumer prices recorded over the past year led to significant adjustments.

The 2026 indexation follows the same logic, with the new indices published in 2026. Our calculator automatically includes the latest figures.

Practical example: lease signed in March 2024, rent EUR 900.

Starting index (February 2024): 129.23
New index (February 2025): 132.47
New rent: 900 × (132.47 / 129.23) = EUR 922.56

Indexation by region

Each Belgian region applies indexation in its own way.

Wallonia

The Walloon Region follows the Walloon Decree of 15 March 2018. Indexation is unrestricted, but limited by the property’s EPC rating.

Brussels

The Brussels Housing Code governs indexation in Brussels. The EPC rules are stricter there (E, F, G ratings are affected).

Flanders

Flanders has its own legal framework with EPC restrictions similar to Wallonia (F, G).

Region	Legal framework	EPC prohibits indexation
Wallonia	Walloon Decree	F, G
Brussels	Brussels Housing Code	E, F, G
Flanders	Flemish Decree	F, G

EPC and indexation ban since 14 October 2023

Since 14 October 2023, a property’s energy performance can limit indexation. The least energy-efficient properties (EPC E, F or G) have their indexation reduced or even prohibited.

These measures aim to encourage landlords to renovate. The rules vary by region and are regularly updated.

Unregistered lease and indexation

An unregistered lease cannot be indexed until it has been declared to the FPS Finance. Registration is free and is the landlord’s responsibility, within 2 months of signing. Three options are available: MyRent online, registered letter or local registration office.

Tool to calculate your indexation

Calculating an indexation manually is tedious. Our online calculator does the work in seconds:

Enter the base rent.
Enter the date the lease was signed.
Choose the indexation date.

The result is accurate, compliant with the official formula, and can be exported as a PDF to send to your tenant.

In summary

Rent indexation is an annual right of the landlord, based on the Statbel health index. It follows a simple formula but must be requested in writing within 3 months. The rules vary by region and the property’s EPC rating. Use our rent calculator to get a reliable result in just a few clicks.