When can a landlord index the rent?

Not every landlord can simply index the rent whenever they wish. Belgian law sets a number of conditions that must all be met simultaneously. In this article we list all the requirements and explain when and how you can proceed.

The 5 conditions

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1. The contract contains an indexation clause
The lease must explicitly provide for the possibility of indexation. Most standard lease agreements include this clause, but it is worth checking.

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2. At least 12 months have passed
You may only index from the first anniversary of the contract onwards. If the lease started on 1 March 2024, the earliest you can index is 1 March 2025.

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3. At least 12 months since last indexation
Have you indexed before? Then you must wait at least 12 months before you can index again.

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4. The EPC label permits indexation
Since 2023, properties with EPC label E, F or G may not be indexed (or only partially). Check the rules for your region.

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5. Written notification to the tenant
Indexation does not happen automatically. You must notify the tenant in writing. Without this letter, the indexation does not take effect.

Timing: when does the new rent apply?

The new rent takes effect on the first day of the month following the written notification.¹ Example: you send the letter on 15 March, then the new rent applies from 1 April.

Did you forget to notify in time? You can still apply indexation retroactively, but maximum 3 months back. Everything older is permanently lost.

The indexation clause: what if it is missing?

Without an indexation clause in the lease, you cannot index the rent.² This is an absolute condition. If your current lease does not contain this clause, you can try to add it at contract renewal, but you cannot impose it unilaterally.

📌 Check your contract Look for terms such as "indexation", "health index" or "art. 1728bis" in your lease. If these are absent, you cannot apply rent indexation.

Regional differences

The basic rules are the same in all three regions, but there are differences in the EPC correction factors and the exact implementation dates. Our rent tool automatically applies the correct rules for Flanders, Brussels or Wallonia.

Check your indexation rights in 30 seconds

Enter your contract date, region and EPC label. The calculator automatically checks all conditions and calculates the new rent.

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Legal sources

Art. 1728bis §1 of the Civil Code: the indexation takes effect on the first day of the month following the notification.
Art. 1728bis §1 Civil Code: indexation is only possible if the lease agreement contains an express provision to that effect.