The tenant refuses the indexation: what to do?
Your tenant disputes or refuses the rent indexation? Here are the legal remedies and the procedure step by step.
Answer in brief
When a tenant refuses the indexation, everything depends on their motive. Three motives are legally valid: unregistered lease (Brussels, Wallonia), miscalculation, or retroactivity over 3 months. All other motives (landlord’s oversight, tenant’s financial situation, rent “already too high”) are invalid and the landlord can assert their right up to the justice of the peace.
Practical rule: before any escalation, verify your own calculation. Half of indexation disputes are resolved by recalculating correctly with the right health indexes.
The VALID refusal motives
A refusal of indexation is legally founded in three precise cases. In these situations, the landlord will not win the case before the justice of the peace as long as the motive is not lifted.
Unregistered lease: indexation not due
The lease’s registration with the competent registration office is mandatory within 2 months of the signature, at the landlord’s charge. In Wallonia (main-residence lease, since 1 September 2018) and in Brussels (where the EPB certificate must also have been provided to the tenant), without registration the right to indexation does not exist, regardless of the elapsed duration. In Flanders, a written lease and a written request suffice (art. 34 of the Flemish Housing Rental Decree).
It is the most radical effect of the absence of registration in those two Regions: the tenant can refuse the indexation without compensation or notice, and the landlord has no remedy as long as the lease is not regularised. Our guide on unregistered leases details the retroactive registration procedure and its tax consequences.
Miscalculation: recalculation necessary
If the landlord made an error in the calculation (wrong index month, formula misapplied, incorrect reference month), the tenant has the right to refuse the exact requested amount. They are not refusing the indexation in principle — they are refusing an incorrect calculation.
The most frequent errors:
- Index of the signature month instead of the month preceding the signature
- Smoothed health index or consumer price index instead of the (non-smoothed) health index published by Statbel
- Anniversary date based on the signature date instead of the lease’s entry into force
- “Cascading” calculation from the last indexed rent instead of from the base rent
Our step-by-step guide on indexation calculation explains each step with a worked example. In case of doubt, our calculator applies the correct formula to your data.
Retroactivity over 3 months: impossible
Article 1728bis, §1 of the Belgian Civil Code limits the retroactive effect of the indexation request to the 3 months preceding the month of the request. If the landlord tries to claim 3, 5 or 8 years of retroactive indexation, the tenant can legitimately refuse the part beyond the last 3 months.
Our dedicated article rent indexation after 5 years quantifies this effect: an 8-year oversight only entitles to 3 months recoverable, the rest is permanently lost. A partial refusal on this basis is legally founded.
The INVALID refusal motives
All other motives don’t hold up before the justice of the peace. Here are the three most frequent, with the counter-arguments to oppose in your reply letter.
”You should have warned me earlier”
Counter-argument: Belgian law imposes no notice before the lease’s anniversary date. Indexation is not automatic (it requires a written request), but it takes effect on the anniversary date as soon as the notification is made — not on a “courtesy” date chosen by the tenant.
Article 1728bis of the Civil Code and the Law of 6 August 1993 on main residence leases mention no obligation of notice. The only constraint is the retroactivity limit: the request only reaches back to the 3 months preceding the month of the request (art. 1728bis, §1).
”The rent is already too expensive”
Counter-argument: the absolute amount of the rent is not a legal motive of refusal of indexation. Indexation follows a strict mathematical formula based on the health index published by Statbel. The “high” character of the rent is a subjective appreciation without legal basis opposable to the landlord.
If the tenant considers the rent disproportionate, they can request a rent revision at the justice of the peace at the triennial renewal of the lease (procedure distinct from indexation, subject to strict conditions).
”I have financial problems”
Counter-argument: the tenant’s financial situation is a human motive but not a legal one. The landlord remains entitled to demand the due indexation. However, it is often the right time to propose an amicable arrangement: spreading the difference over 6 or 12 months, temporary indexation freeze in exchange for a guarantee, etc.
A formal refusal on this motive will be rejected by the justice of the peace. But a written amicable compromise (lease addendum signed by both parties) sustainably protects the rental relationship.
Recommended procedure in 3 steps
Faced with a refusal of indexation, methodically follow this progression. Never go directly to court without having exhausted steps 1 and 2.
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Verify your own calculation. Before responding to the refusal, redo the calculation on our calculator. Verify: exact signature date, month of the reference index (month preceding the signature), month of the new index (month preceding the anniversary date), applied formula. An error on your side completely changes the deal — better correct it before hardening the tone.
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Re-notify by motivated registered mail. Send a second written request, by registered mail with acknowledgment of receipt, containing: reference to article 1728bis of the Civil Code and to the Law of 6 August 1993, calculation detail (used health indexes, formula, dates), new monthly rent, effective date, and PDF proof of the calculation as an attachment. This documented reminder often makes a good-faith tenant yield who had simply misunderstood.
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Formal notice then justice of the peace. If the registered reminder remains without effect within 15 days, send a formal notice by registered mail, with a final 15-day deadline. Without response, refer to the territorially competent justice of the peace (property’s commune). The procedure is inexpensive, without mandatory lawyer.
The justice of the peace: what to expect
It is the Belgian jurisdiction competent for all rental disputes, including indexation refusal. Here is the concrete progression for a landlord who has never referred to this instance.
Cost: the procedure is not free, but inexpensive (2026 amounts). A 26 euro contribution to the legal aid fund is paid when filing the petition; a 50 euro court registry fee is claimed at the end of the proceedings from the party ordered to pay the costs. Only conciliation is free. No mandatory lawyer — you can represent yourself. Many landlords do.
Delay: the registrar summons the parties to appear in principle within 15 days of the petition being entered on the roll (art. 1344bis Judicial Code). The time to a decision varies by canton.
Decision: if your calculation is correct and the lease registered, the judge orders the tenant to pay the due arrears within the limit of the 3 months preceding the month of the request, plus the new indexed rent from the effective date. The tenant is also in principle ordered to pay the costs of the proceedings (art. 1017 Judicial Code), including the court registry fee.
Concrete procedure example: Brussels lease of €950/month, registered, EPB C provided to the tenant, signed on 20 February 2020 and in force since 1 March 2020, never indexed. In March 2026, the landlord calculates the due indexation: 950 × 138.06 (February 2026) ÷ 109.72 (January 2020) = €1,195.38. The tenant refuses by SMS invoking “an already too high rent”. The landlord sends a motivated registered reminder in late March (step 2). Without response, formal notice in mid-April (step 3). Without response, petition filed at the justice of the peace of Brussels in late April, with the €26 contribution paid at filing. Decision: tenant ordered to pay the rent difference since March 2026 (€245.38 per month, i.e. €736.14 for March, April and May) + the costs, new rent of €1,195.38 effective since March 2026. The €50 court registry fee is claimed from the tenant, as the party ordered to pay the costs.
Useful letter templates
Three templates cover the entire refusal management procedure:
- Indexation notification to the tenant — the first request, to send each year on the anniversary date
- Formal notice letter — step 3 of the procedure, to send by registered mail with a 15-day deadline
- Registered mail slip — systematically to attach for formal proof of the date of the request
All templates integrate the mandatory legal references (article 1728bis of the Civil Code, Law of 6 August 1993) and the indexation calculation detail.
Going further
Frequently asked questions
Can the tenant refuse an indexation if not warned in advance? + −
No. Belgian law imposes no notice before the anniversary date. Indexation applies at the earliest on the anniversary date once requested in writing, and the absence of prior warning is not a valid refusal ground. The tenant cannot demand a courtesy delay either.
What to do if the tenant completely ignores the indexation request? + −
First send a registered formal notice with acknowledgment of receipt, granting a 15-day deadline to regularise. Without response, you can refer to the justice of the peace of the property's commune. The procedure is inexpensive and requires no lawyer; the parties are in principle summoned within 15 days of the petition being entered on the roll (art. 1344bis Judicial Code), and the time to a decision varies by canton.
Does the tenant have the right to dispute the calculation? + −
Yes, and it is even a perfectly valid refusal ground if the calculation is wrong. Systematically verify your calculation before any escalation: health indexes of the right month, correct formula, exact signature date. In case of error on your part, recalculate and re-notify.
Is the justice of the peace really free? + −
No, it is not free, but it is inexpensive. Two fees apply (2026 amounts): a 26 euro contribution to the budget fund for second-line legal aid, paid by the claimant when filing the petition, and a 50 euro court registry fee, claimed at the end of the proceedings from the party ordered to pay the costs. Only conciliation, which is optional for residential leases, is free. No mandatory lawyer. The costs are in principle borne by the losing party (art. 1017 Judicial Code).
How many months of arrears can I claim if the tenant has been refusing for a long time? + −
Maximum 3 months: the indexation request has retroactive effect only for the 3 months preceding the month of the request (article 1728bis, §1 of the Civil Code). Even if the refusal has been going on for 3 or 5 years, only the arrears of the last 3 months preceding the month of the request are recoverable. The rest is permanently lost. For the future, however, the fully indexed rent applies.
Can I terminate the lease if the tenant refuses to pay the indexation? + −
Not directly for that sole reason. However, if the tenant doesn't pay the sums due after conviction by the justice of the peace, characterised non-payment can justify a request for resolution of the lease in a subsequent procedure.
Calculate your indexation
Our tool automatically applies the Belgian legal formula with up-to-date Statbel indexes.
Go to the calculator →This article is informational and does not constitute legal advice. For any disputed or complex situation, consult a lawyer or the justice of the peace of the property's commune (low-cost procedure, no lawyer required).