Formal notice letter (refusal of indexation)
To use when your tenant disputes or doesn't pay the indexation after your initial notification. It is the usual step before referring to the justice of the peace.
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Avenue Louise 367
1050 Brussels
RECIPIENT (to send by registered mail)
Jean Vandenberghe
Rue Haute 142
1000 Brussels
Subject: Formal notice to pay the due indexation — Rue Haute 142, 1000 Brussels
Dear Sir or Madam,
By letter dated 1 July 2026, I notified you of the annual indexation of the rent relating to the property you occupy under the lease signed on 14 June 2021 and effective from 1 July 2021.
As of today, 45 days after this notification, the indexed rent supplement remains unpaid. I hereby formally notify you to proceed with payment as soon as possible.
I remind you that the indexation, provided for by article 1728bis of the former Civil Code, was requested from you in writing, and that the conditions of article 224/2 of the Brussels Housing Code are met: the lease is registered and the energy certificate has been provided to you.
Awaiting your payment, yours faithfully.
Signature,
Marie Dupont
When to send a formal notice?
Three typical situations that justify a formal notice:
- The tenant doesn't pay the supplement — they continue to pay the old rent after your indexation notification.
- The tenant disputes the calculation — they write to you that they disagree with the amount.
- The tenant ignores your letter — no response, no full payment, no explicit dispute.
Registered mail strongly recommended
Registered mail is strongly recommended so that you have dated proof; the formal notice is the usual step before referring to the justice of the peace. An acknowledgment of receipt strengthens that proof further.
Without proof of dispatch, it will be harder to establish before the judge that the tenant was indeed given formal notice, and on which date.
And after the 15 days?
If the tenant has still not regularised after the deadline given in the formal notice:
- Refer to the justice of the peace of the property's commune — low-cost procedure (2026 amounts: a €26 contribution when filing the petition, plus a €50 court registry fee charged to the losing party; conciliation is free), no lawyer required
- Attach the documents: registered lease, initial notification letter + acknowledgment of receipt, formal notice letter + acknowledgment of receipt, detailed calculation of the indexation
- Hearing: summons 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
- Judge's decision: if your calculation is correct, the tenant is in principle ordered to pay the supplement + the costs of the proceedings
Frequently asked questions
When to use this letter? + −
When the tenant disputes or doesn't pay the indexation after your first notification. It's the step before referring to the justice of the peace.
What deadline to grant? + −
15 days from receipt of the registered mail. Reasonable and standard deadline for a formal notice. Beyond that, you can refer to the justice of the peace.
Should it be sent by registered mail? + −
It is strongly recommended. Registered mail (ideally with acknowledgment of receipt) gives you dated proof of dispatch and receipt, useful if you then have to refer the case to the justice of the peace.
What if the tenant still doesn't pay after 15 days? + −
You refer to the justice of the peace of the property's commune. The procedure is not free but inexpensive (2026 amounts): a €26 contribution to the legal aid fund, paid when filing the petition, plus a €50 court registry fee, claimed at the end of the proceedings from the party ordered to pay the costs. No lawyer is required. The judge decides: if your calculation is correct, the tenant is in principle ordered to pay the supplement and the costs.
Can the tenant refuse the indexation due to poor maintenance? + −
No. Maintenance and indexation are two separate matters. The tenant who complains about maintenance can bring another action in court, but cannot unilaterally refuse to pay the indexation.
Related templates
- Initial notification letter — to send first
- Registered mail slip — to attach
- Complete example