Rent indexation in Belgium: rules, calculation and energy performance

Every year, rent indexation in Belgium raises the same questions: is it due, how is it calculated and can it be claimed retroactively? Since the energy crisis of 2022, the energy performance certificate of the property has also played a role. This article sets out the rules for residential leases in Brussels (Brussels Housing Code, Brusselse Huisvestingscode / Code bruxellois du Logement) and in Flanders (Flemish Residential Tenancy Decree, Vlaams Woninghuurdecreet). Wallonia has its own rules, which are not covered here.

When can the rent be indexed?

Rent indexation is only possible if the following conditions are met:

• the lease is in writing and does not expressly exclude indexation;
• indexation takes place at most once per rental year, at the earliest on the anniversary of the date the lease took effect;
• indexation is not automatic: the interested party, in practice the landlord, must request it in writing;
• in Brussels, the lease must also have been registered and the landlord must have provided the tenant with the energy performance certificate (EPB certificate / certificat PEB), under Article 224/2 of the Brussels Housing Code.

Calculating rent indexation in Belgium: the statutory formula

The statutory formula is: base rent x new index / starting index. A clause allowing a higher adjustment than this formula is reduced to the statutory adjustment.

• Base rent: the rent agreed in the lease, excluding costs and charges.
• Starting index: the health index (gezondheidsindex / indice santé) of the month preceding the month in which the lease was concluded; in Flanders, of the month preceding the month in which the lease took effect (Article 34 § 2 of the Flemish Residential Tenancy Decree).
• New index: the health index of the month preceding the anniversary of the date the lease took effect.

Note the difference: in Brussels, the starting index depends on the date the lease was signed, the new index on the date it took effect. These two dates do not always coincide. In Flanders, both indices are based on the date the lease took effect.

The index figures and a calculation tool are available on the Statbel website. Mistakes in the month used or in the base rent are common, and they accumulate year after year. Always keep the lease and any previous indexation requests to hand.

A fictitious worked example

Suppose the base rent is 1,000 euros, the starting index 120.00 and the new index 126.00. The indexed rent is then 1,000 x 126.00 / 120.00, or 1,050 euros. The following year, the calculation again starts from the base rent of 1,000 euros and the starting index, with the new index applicable at that time.

How does the landlord request indexation?

A proper request is made in writing and states the base rent, the index figures used, the new rent and the date from which it is due. This allows the tenant to check the calculation. A tenant who is in doubt is well advised to pay under reserve and to ask for an explanation in writing.

Retroactive effect: limited to three months

If the landlord requests indexation late, it only applies retroactively to the three months preceding the month of the request. Years of missed indexation therefore cannot be claimed in one go. The request itself may be made by letter or email, as long as it is in writing and can be proven. Because the formula always starts from the base rent and the new index, the fully indexed rent does, however, apply immediately for the future.

Restrictions based on the energy performance certificate

During the energy crisis, both Regions temporarily restricted indexation for properties with poor energy performance. That period is over, but for older leases it still has an effect through a correction factor.

Flanders: EPC label and correction factor

From 1 October 2022 to 30 September 2023, indexation depended on the EPC label: in full for labels A, B and C, by half for label D, and not at all for labels E and F or where there was no EPC. Since 1 October 2023, indexation has been allowed again. For leases that took effect before 1 October 2022 and concern a property with label D, E or F or without an EPC, a correction factor applies, however (Flemish Decree of 3 October 2022), so that the missed indexation is not simply recovered.

Brussels: EPB label and correction factor

From 14 October 2022 to 13 October 2023, indexation for energy-inefficient properties was restricted or excluded, depending on the EPB label. Since 14 October 2023, indexation has been allowed again, but for leases already running on 14 October 2022 concerning a property with label E, F or G, an adjusted formula with a correction factor applies (Article 224/2 of the Brussels Housing Code).

The correct calculation therefore depends on the Region, the date of the lease, the anniversary date and the energy certificate. The authorities provide calculation tools; have any disputed calculation checked.

What about costs and charges?

The indexation formula only applies to the base rent. Costs and charges must in principle correspond to actual expenses, unless a fixed amount was expressly agreed. In Brussels, either party may ask the justice of the peace (vrederechter / juge de paix) to revise a fixed amount or convert it into actual costs, and for leases concluded or renewed since 1 November 2024 the landlord must provide a separate annual statement of charges (Article 224/3 of the Brussels Housing Code).

Indexation is not a rent review

Separately from indexation, the rent can be reviewed in both Regions at the end of each three-year period, by mutual agreement or by the justice of the peace. Strict time limits apply before the end of that period: anyone who misses them must wait for the next three-year period.

As a rule, the court only grants a review if the normal rental value has risen or fallen significantly due to new circumstances, or has increased as a result of works carried out by the landlord. In Brussels, since 1 November 2024, an increase following a review is only payable if the lease has been registered (Article 240 of the Brussels Housing Code). More on drafting a residential lease.

Frequently asked questions

My landlord has been indexing the rent for years by direct debit without asking. Is that allowed?

Indexation requires a written request. Amounts overpaid can be recovered under certain conditions. Have the calculation checked before you pay or claim a refund.

Which index applies: the ordinary index or the health index?

For residential leases, the health index applies, published monthly by Statbel. Among other things, this index excludes alcoholic beverages, tobacco and motor fuels. If your lease refers to a different index, have the calculation checked.

Can the landlord increase the rent after energy-saving works?

In Brussels this is possible under certain conditions: the parties must expressly agree on the increase no later than one month before the works, and the increase must be proportionate to the improvement in energy performance, the cost to the landlord and the savings for the tenant. In the event of disagreement, the joint rental committee (paritaire huurcommissie / commission paritaire locative) can issue an opinion (Article 221 of the Brussels Housing Code). In both Regions, works carried out by the landlord may also justify a review at the end of a three-year period.

Does indexation also apply to a short-term lease?

Yes, under the same conditions: a written lease, a written request and no more than one indexation per rental year. The additional Brussels conditions mentioned above also apply.

And for commercial leases?

Commercial leases are not subject to the rules for residential leases. Indexation then follows the indexation clause in the lease, within the statutory limits. Unlike residential leases, the contract may provide that indexation takes place automatically, without a separate request. More on commercial leases.

How Novex Advocaten can help

A dispute about indexation, a correction factor or a rent review? We check the calculation and defend your position, amicably or before the justice of the peace. Find out how a rental dispute before the justice of the peace proceeds.

Call 0484 99 22 72 or email asfour@novexadvocaten.be.