In Wallonia rent is indexed once a year, on the lease anniversary, using the health index. The formula is: new rent equals the base rent multiplied by the health index of the month before the anniversary, divided by the health index of the month before the lease started. Indexation needs a written, registered lease and a valid EPC.
Indexation lets a landlord adjust rent to the cost of living without renegotiating the lease. In Wallonia it can be applied only once per year, no earlier than the anniversary of the lease start, and only if the lease is in writing and registered (indexation-loyer.be, 2026). It is not automatic: the landlord must request it, and the increase can be backdated by at most three months, so a landlord who forgets loses the earlier catch-up.
The calculation uses the health index (indice sante), the filtered version of the consumer price index. The standard formula is: new rent equals base rent multiplied by the new health index divided by the starting health index (indexation-loyer.be, 2026). The “new” index is that of the month before the anniversary date, and the “starting” index is that of the month before the lease began. As an illustration only, a base rent of 800 euros with a starting index of 111 and a new index of 132 would give roughly 951 euros; the real figures come from the official monthly index published for the relevant months.
A crucial condition since the temporary energy measure ended is the EPC. A valid EPC (PEB) certificate is required to index the rent in Wallonia, even though the energy label itself no longer changes the amount (certinergie.be, 2026). Between November 2022 and October 2023 the label did modulate indexation, but that mechanism was dropped on 1 November 2023, and full indexation by the standard formula has applied since (indexation-loyer.be, 2026).
The counter-intuitive twist is regional divergence. In Wallonia the EPC no longer caps indexation, yet in Brussels a correction factor still bites on older leases for poor labels, and Flanders has programmed future bans on indexing or even renting low-rated homes. So the same F-rated property is indexed differently depending on the region it sits in.
At a glance
| Element | Rule in Wallonia |
|---|---|
| Frequency | Once per year, from the lease anniversary |
| Formula | Base rent x (new health index / starting health index) |
| New index | Month before the anniversary date |
| Starting index | Month before the lease start |
| Conditions | Written, registered lease and a valid EPC |
| Backdating | Maximum three months |
| EPC effect on amount | None since 1 November 2023 |
| Regional note | Brussels and Flanders apply EPC corrections or future bans |