Sample rent indexation letter for Belgium: free template + explanation

Last reviewed on 2026-06-10 · reading time ± 3 min

Rent indexation does not happen automatically in Belgium: as a landlord, you must notify the tenant in writing. A registered letter is not required, but dated written proof (letter or e-mail) is essential — the indexation only works back three months from your request.

What must the letter contain?

A correct indexation letter contains at least:

• identification of the rented property and both parties;
• the basic rent from the contract;
• the starting index and the new index (Statbel's health index), stating the month and base year;
• the legal formula: basic rent × new index ÷ starting index;
• the new rent amount and the date from which it applies;
• where applicable: the correction factor for the EPC/EPB label.

Sample letter

[Landlord's name]
[Landlord's address]

[Tenant's name]
[Tenant's address]

[Place], [date]

Subject: annual rent indexation — [property address]

Dear [tenant's name],

In accordance with Article 1728bis of the (old) Belgian Civil Code and
the provisions of the lease, I am adjusting the rent to the health
index, using the formula basic rent × new index ÷ starting index.

  • Basic rent: € [amount]
  • New index ([month year]): [value]
  • Starting index ([month year]): [value]
  • New rent: € [amount], due from [date]

I am happy to answer any questions about the calculation.

Kind regards,
[Landlord's name]

Note: the correct index months and any correction factor depend on your region, the contract's start date and the energy label. Don't work that out in your head.

Generate your letter automatically (free)

Our calculator fetches the right index figures, applies the correction factor where needed and turns everything into a ready-made letter you can print or copy.

Common mistakes

The three mistakes we see most often: (1) using the consumer price index instead of the health index, (2) picking the wrong starting month (signing vs entry into force — this differs per region and start date), and (3) forgetting the EPC correction factor for Flemish contracts from before October 2022 with label D, E or F. Each of these mistakes makes the requested rent contestable.