Belgian rent indexation: the rules in all three Regions

Yes, in principle, but not on its own: the landlord must ask for indexation in writing, at the earliest on the lease anniversary, once a year, and only if the lease does not rule it out. The formula is the same across the country. The conditions on registration and on the energy certificate (PEB) change from one Region to the next.

Can my landlord index my rent?

Yes, on four conditions found in all three Regions:

• the lease contains no clause ruling out indexation;
• the anniversary of the lease's start date has passed, because you cannot index before it, nor more than once a year;
• the request is in writing, the Public Service of Wallonia (SPW) specifying that an ordinary letter, a text message or an e-mail is enough, with proof kept;
• the Region's formalities are met, such as registration of the lease or a valid PEB.

Nothing is automatic. A tenant who receives no request simply keeps paying the current rent.

Who decides the rules: the Region, not the federal State

Residential leases have been a Regional matter since the sixth reform of the State, whose regionalisation law dates from 6 January 2014. Brussels adopted its ordinance on 27 July 2017, in force on 1 January 2018, Wallonia its decree of 15 March 2018, and Flanders applies its own decree on residential leases: one landlord can therefore follow three different sets of rules depending on where the properties are.

The index, though, stays national: Statbel publishes it. The split between levels of government is covered in our article on Regions and Communities.

How is rent indexation calculated in Belgium?

With a rule of three: new rent = base rent × new index ÷ starting index. The base rent is the one in the lease, excluding charges. The starting index is the health index of the month before the lease was signed, and the new index is that of the month before the lease anniversary. This is the formula published by the SPW and the Brussels Region.

A worked example. An 800 euro lease is signed in April 2025: the starting index is March 2025's, which is 135.91 (2013 = 100). At the April 2026 anniversary, the new index is March 2026's, which is 137.78. The calculation gives 800 × 137.78 ÷ 135.91, or 811.01 euros. The increase is 11.01 euros a month, 1.38%.

Both indices come from the table published by indexation-loyer.be, which cites Statbel as its source. Check them on Statbel's site before sending a letter.

Where can I find the month's health index?

At Statbel. Every month, without exception. The health index is consumer prices excluding tobacco, alcohol and motor fuels, used for rents since 1994 according to the SPW. Statbel's rent calculator, recommended by the Flemish Region, does the sum for you.

How many months back can the landlord claim?

Three, no more. A landlord who forgets to index can still do so later, but the right to arrears is limited to the three months before the request, according to the SPW. Brussels and Flanders set the same limit.

Take the 800 euro lease again, anniversary on 1 April 2026, an increase of 11.01 euros a month. If the request arrives in July, the landlord can claim April, May and June: 3 × 11.01, or 33.02 euros, then 811.01 euros every month. If it only arrives in October, only July, August and September can be claimed. The 33.02 euros from April to June are lost.

What does Wallonia provide?

A principal-residence lease must be registered since 1 September 2018, according to the SPW. According to La DH of 2 September 2026, registration is a precondition for indexing a residential lease in Wallonia.

Then there is the energy certificate (PEB). The decree of 19 October 2022 framed indexation for anniversaries falling between 1 November 2022 and 31 October 2023:

• A, B and C dwellings were indexed normally;
• a D could pass on only 75% of the difference, an E only 50%;
• F and G dwellings, or those without a certificate, could not be indexed.

The cap is calculated as (indexed rent − rent due) × 75 or 50%. For D to G dwellings, the rent adapted in this way became the base for later indexations, from 1 November 2023. The Constitutional Court dismissed a challenge to this decree in its judgment no. 64/2024.

What does Brussels require?

A registered lease and a valid energy certificate (PEB), handed to the tenant. Two conditions, not one. The certificate must be valid when the request is made: if it has expired, a new one must be supplied before any indexation.

Until 13 October 2023, indexation of energy-hungry dwellings was restricted. Since 14 October 2023 it has been allowed again for E, F and G dwellings, with a correction factor if the lease began before 14 October 2022. The legal basis is Article 224/2 of the Brussels Housing Code, amended by the ordinance of 13 October 2023. According to La DH, landlords must also register on Irisrent since 2025.

How does Flanders correct for low-rated dwellings?

With a correction factor, applied at each indexation. It covers leases that began before 1 October 2022 for a dwelling rated D, E, F or without a valid PEB. Later leases are indexed normally.

The factor depends on the anniversary month. For July, the official page gives 0.976119286 for a D and 0.952238571 for an E, an F or a missing PEB, which amounts to an indexation roughly 2.4% then 4.8% lower than without the correction, and the factor then changes with each anniversary month according to a table the Region publishes. It stops with an A+, A, B or C certificate, or with a new lease. On 21 March 2024, the Constitutional Court ruled that the limit also applies to student leases.

Another Flemish particularity: if the request arrives after the anniversary, the official page says the index of the notification moment is the one that counts. Use Statbel's calculator.

My indexed rent looks too high: what can I do?

Check five things: the lease clause, the anniversary date, the written request, the two indices and the Region's rules. The table sets the common cases side by side.

If the two sides disagree, the justice of the peace (juge de paix) has jurisdiction in Flanders, and the Info-Conseils Logement advice desks answer in Wallonia.

This article describes rules, not political choices. The parties' positions on rents are in the comparison on rent control. The comparator puts two parties side by side and the ranking summarises positions by topic. The scores reflect a position on an axis, not a quality, as the methodology explains.

Sources: Public Service of Wallonia, Indexer un loyer (updated 23 July 2026); Brussels-Capital Region, Rent indexation; Vlaanderen, De huurprijs and Huurprijsindexatie met correctiefactoren; Wallex, decree of 19 October 2022 amending Article 26 of the decree of 15 March 2018 on residential leases; IRIB, note on the regionalisation of residential leases; Statbel, health index; indexation-loyer.be, 2026 health index table (March 2025 and March 2026 values, citing Statbel); La DH, rent indexation in Brussels and Wallonia, 2 September 2026. The worked example (811.01 euros, 11.01 euros a month, 33.02 euros of arrears) is recalculated from these indices and applies to a fictional lease.