Rent Indexation Calculation in Belgium

The four elements of the calculation

The base rent

The base rent is the amount set at the time of signing the lease. It appears in the original lease contract. It is not the rent currently being paid, but the initial amount agreed between the landlord and the tenant when the contract entered into force.

If the rent has been revised during the lease (amicable agreement or decision by the justice of the peace), the new agreed amount becomes the base rent for future indexations.

The starting health index

This is the health index for the month preceding the signing of the lease. If the lease was signed on 15 March 2020, the starting index is the one for February 2020. This index is fixed for the entire duration of the lease and never changes.

The new health index

This is the health index for the month preceding the anniversary of the lease coming into force. If the lease came into force on 1 April 2020, the new index for the 2026 indexation is the one for March 2026.

Health indices are published monthly by Statbel (the Belgian statistical office). Consult our health index table to find the exact values.

The EPC correction factor

Since 2022-2023, a coefficient linked to the energy performance class of the property applies in all three Belgian regions. This factor ranges from 0 (total block) to 1 (full indexation).

For details by region: EPC restrictions and indexation.

Practical calculation examples

Example 1: standard lease with EPC B in Wallonia

A lease signed on 10 January 2022, base rent of 750 euros. EPC B (factor = 1.00).

• Starting health index: December 2021 (month preceding the signing) = 116.09 (indicative value)
• New health index: December 2025 (month preceding the anniversary in January 2026) = 134.80 (indicative value)
• Calculation: 750 x (134.80 / 116.09) x 1.00 = 870.80 euros

The landlord may request 870.80 euros per month from 10 January 2026.

Example 2: lease with EPC F in Wallonia (blocked)

Same lease, but the property is rated EPC F. The EPC factor in Wallonia for an EPC F is 0.00.

• Calculation: 750 x (134.80 / 116.09) x 0.00 = 0 euros of indexation

The rent remains at 750 euros. The landlord cannot index until the energy class is improved. See rent indexation in Wallonia.

Example 3: lease in Brussels with EPC E

A lease entered into force on 1 June 2023, base rent of 950 euros. EPC E, Brussels correction factor = 0.60 (indicative value).

• Starting index: May 2023
• New index: May 2026
• Theoretical calculation without EPC: 950 x (new index / starting index) = gross amount
• Application of the factor: gross amount x 0.60 = reduced indexed rent

The landlord may only claim 60% of the theoretical increase. For the exact calculation: rent indexation in Brussels.

Impact of the EPC factor on the calculation by region

The EPC factor significantly modifies the final result. For the same base rent and the same indices, the indexed amount varies depending on the region and the energy class.

Wallonia: strict block

Wallonia applies a binary system for the lowest EPC ratings: full indexation for A to D, partial for E, nil for F and G. A property without a valid EPC certificate is treated as EPC G. See indexation in Wallonia.

Brussels: progressive factor

Brussels uses a more nuanced correction factor. The reduction is proportional to the energy class, with annual adjustments by ordinance. See indexation in Brussels.

Flanders: own rules

The Flemish Region has its own regulatory framework via the Vlaams Woninghuurdecreet. EPC restrictions also apply but with specific modalities.

For a detailed comparison: rent indexation Belgium: 3-region comparison.

Common calculation errors

Using the wrong starting index

The starting index is the one for the month preceding the signing of the lease, not the month of the signing itself or the month of entry into force. If the lease was signed on 5 March 2020, the starting index is the one for February 2020.

Confusing the signing date with the date of entry into force

The new index is based on the anniversary of the lease’s entry into force, not its signing. These two dates may differ by several weeks.

Forgetting the EPC factor

Since 2022-2023, a calculation without the EPC factor is incomplete. A landlord who omits this factor risks claiming an excessive amount and facing a challenge from the tenant.

Rounding incorrectly

The indexed rent is calculated to the nearest cent. A result of 843.456 euros gives 843.46 euros. Rounding to the nearest whole euro (844 euros) is an error.

Indexing an unregistered lease

A lease not registered with the FPS Finance gives no right to indexation. The landlord must first register the lease before being able to index.

For a detailed list of errors: common indexation errors.

Tools for calculating indexation

BailBelgique calculator

Our free indexation calculator automatically integrates up-to-date health indices, applies regional EPC factors and generates a ready-to-send indexation letter.

Manual verification

For manual verification, you need the original lease contract (base rent and signing date), the health indices from the index table and the applicable EPC factor for your region.

Tenant verification

If you are a tenant and receive an indexation request, our tenant verification tool allows you to check the calculation in seconds.

Indexation calculator — Indexation letter template — Indexation pillar guide.