What every landlord should know about the legal rules for indexation in Flanders, Brussels and Wallonia — including the 2026 situation.
Since the sixth state reform, residential tenancy law is a regional matter. Flanders applies its Housing Rent Decree, Brussels its Housing Code, and Wallonia its 2018 decree. Despite these separate texts the basic formula is the same everywhere: base rent x new health index / initial index. What differs from Region to Region are the conditions and the energy-related restrictions. Commercial leases remain governed by the federal Commercial Tenancy Act.
Four conditions must be met. The lease must be in writing and registered with the Federal Public Service Finance — registration is free and compulsory for residential leases. Indexation must be provided for in the contract or permitted by law. The property must have a valid energy performance certificate. Finally, indexation is never automatic: the landlord has to request it in writing from the tenant. Without that request the rent stays unchanged, even where the right exists.
Between 1 October 2022 and 30 September 2023 Flanders froze indexation for energy-inefficient homes. That freeze has ended, and every landlord may index again regardless of label. However, the decree of 4 July 2023 made a correction factor permanent for residential leases that took effect before 1 October 2022 with label D, E or F, or without a valid EPC. This factor is below 1 and prevents the frozen year from being recovered later. Labels A, B and C index in full. Our platform calculates the factor automatically.
The ordinance of 11 October 2022 introduced a comparable freeze from 14 October 2022. Since 14 October 2023 indexation is allowed again. A correction coefficient still applies to leases that took effect before 14 October 2022 where the property is rated EPB E, F or G. That coefficient comes from an official table and depends on both the label and the anniversary month of the lease. For more recent leases the standard calculation applies. We flag such contracts automatically so the correct coefficient is used.
What every landlord should know about the legal rules for indexation in Flanders, Brussels and Wallonia — including the 2026 situation.
Wallonia took a different route: its EPB-related restriction ended definitively on 1 November 2023 and was not replaced by a correction factor. Since then every Walloon residential lease is indexed using the ordinary federal formula, whatever the energy rating. The 2018 Walloon decree still governs the rest: the lease must be registered, indexation must be requested in writing, and it takes place on the anniversary of the lease taking effect. A valid EPB certificate remains compulsory when letting.
Indexation may only take place on the anniversary of the date the lease took effect — not the signing date, unless the two coincide. It applies going forward: you cannot claim years of arrears. A written request has retroactive effect for a maximum of three months from the date it is sent. Indexation forgotten for two years therefore cannot be recovered: beyond three months the difference is permanently lost.
Indexation is a statutory right of the landlord once all conditions are met. If your tenant challenges the increase, you can refer to the legal framework and the official index figures published by Statbel. Our indexation letters always set out the full calculation: base rent, initial index, new index, any correction factor and the effective date. That transparency prevents most disputes, because the tenant can verify every figure.
Our platform applies the correct legislation based on Region, lease type and energy label. When registering the contract you provide the Region, signing date, start date and EPC. From that the system determines the correct initial index, applies a correction factor where required, and stops the calculation when data is missing rather than producing a wrong result. You do not have to follow legal developments yourself.
Enter your base rent, start date and region and see straight away what you may charge this year. Based on the official health index, with the Flemish EPC correction applied automatically.
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