Every year, on the lease anniversary, the Belgian landlord may index the tenant's rent. It's a right provided by law, but it follows precise rules: an official formula, a reference index, and nuances depending on the region. Here's how it works, step by step.
Indexation is the annual adjustment of rent to the evolution of the cost of living, measured by the health index. It allows the rent to follow inflation without renegotiating the lease. It's not automatic: the landlord must request it in writing, and can only claim it retroactively over the last three months.
Indexation is possible once a year, at the earliest on the anniversary of the lease coming into effect. A lease that took effect on 1 May can only be indexed from 1 May of the following year. At least one year must have elapsed.
The calculation: 800 × 139.33 ÷ 134.77 = €827.06. An increase of 3.4%, matching the evolution of the health index over the year.
The health index is published monthly by Statbel, the Belgian statistics office. Note: since January 2026, the reference base changed from 2013=100 to 2025=100. For a correct calculation, the starting index and the new index must be expressed in the same base.
Calculating indexation by hand, finding the right index in the right base, drafting the tenant letter: it's doable, but tedious and error-prone. A tool like Domavix does it automatically: it detects leases reaching their anniversary, calculates the new rent by region, and generates the indexation letter ready to send.
Domavix calculates the indexation, applies the new rent and prepares the tenant letter. Free to start.
Try Domavix →This article is for informational purposes only and does not constitute legal advice. Indexation rules may change; always verify the official index values and the applicable regional regulations.