Indexation notification letter to the tenant
The standard letter to notify the annual rent indexation to your tenant, to be sent each year on the lease's anniversary date. A4 format, compliant with article 1728bis of the Belgian Civil Code.
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Avenue Louise 367
1050 Brussels
RECIPIENT
Jean Vandenberghe
Rue Haute 142
1000 Brussels
Subject: Annual rent indexation — anniversary date 1 July 2026
Dear Sir or Madam,
In accordance with article 1728bis of the Belgian Civil Code, I hereby notify you of the annual indexation of the rent relating to the property located at Rue Haute 142, 1000 Brussels, subject of the lease signed on 14 June 2021 and effective from 1 July 2021.
Applied formula: Initial rent × (New index ÷ Base index) × EPC coefficient.
That is: 850.00 × (132.47 ÷ 110.99) × 100 % = €1,015.83.
Variation: + €165.83/month.
Yours faithfully,
Signature,
Marie Dupont
What should this letter contain?
The law requires few formal mentions, but in practice an indexation notification letter should include:
- Identification: name + address of the landlord, name + address of the tenant
- Lease reference: signature date, effective start date, property address
- Legal mention: reference to article 1728bis of the Civil Code and to the Law of 6 August 1993
- Calculation detail: base health index + new index + formula + EPC coefficient where applicable
- New rent amount and effective date
- Landlord signature
Recommended sending method
The law does not require registered mail — a simple letter is legally sufficient. But in practice, we systematically recommend registered mail with acknowledgment of receipt, for 2 reasons:
- Proof of date: in case of dispute, you prove that the notification was indeed made within the legal deadlines (3 months max after the anniversary date).
- Proof of receipt: if the tenant disputes having received the letter, the acknowledgment of receipt prevails.
To generate your own personalised letter
Our calculator automatically generates a personalised PDF letter with your lease (your names, your rent, your indexes, your EPC). Easier than filling in an empty template.
Frequently asked questions
When to send this letter? + −
On the anniversary date of the lease's effective start, or within the 3 months that follow. Beyond that, indexation is lost for the unclaimed period.
Should it be sent by registered mail? + −
The law only requires a written letter. A simple letter is legally sufficient. But to keep proof of dispatch in case of dispute, registered mail with acknowledgment of receipt is strongly recommended.
Should supporting documents be attached? + −
Not mandatory, but advised: copy of the lease, calculation detail (indexes and formula), possibly the EPC. Our calculator automatically generates the letter with all the detail.
What if the tenant doesn't respond? + −
No need to wait for a response. Indexation is a right as soon as the written notification has been made. The new rent is due from the anniversary date.
Related templates
- Formal notice letter — if the tenant does not pay
- Registered mail slip — to attach to your dispatch
- Complete example — pedagogical version with real values
- Calculator — for a 100 % personalised letter