The maths is right, the percentage is within the cap… but the rent doesn't go up. This is the most common mistake we see: a landlord calculates the IRL revision perfectly, then never sends a letter — or sends an incomplete one by email. Yet until the tenant has been notified in writing, only the old rent is legally owed. The revision is neither automatic nor retroactive beyond the notification, and the right to claim it expires after one year. Here is exactly what the letter must contain, how to send it, and a ready-to-use template.
Why a written letter is essential
The annual revision under Article 17-1 of the Act of 6 July 1989 is an option, not an automatic mechanism. The landlord must express the intention to apply it and must be able to prove the date. Without notification, the tenant still owes the old amount, and a late claim cannot be recovered on past months.
Two practical consequences: notify as soon as possible after the lease anniversary (every month of delay is a lost revised payment), and keep enforceable proof of delivery.
Mandatory mentions
A solid revision letter must include:
- The identity and address of the landlord and the tenant.
- The lease signing date and a reminder of the indexation clause invoked (art. 17-1, Act of 6 July 1989).
- The reference IRL (quarter + value) and the applicable IRL (quarter + value).
- The calculation: old rent excl. charges × applicable IRL ÷ reference IRL.
- The new rent excluding charges and the effective date.
- Where relevant, a reminder that the property is rated A to E on the DPE (revision is banned for F and G — see our dedicated article).
Registered mail or plain letter?
The law imposes no particular form, but in a dispute it is up to the landlord to prove when and what was notified. A registered letter with acknowledgement of receipt is the only method offering that dual proof. An email or plain letter may be fine while the relationship is healthy but becomes useless the moment there is a dispute.
Keep the acknowledgement of receipt. It fixes the date from which the new rent is owed.
Worked example
Current rent €750 excl. charges, lease signed 1 March 2024, anniversary 1 March 2026, reference IRL Q1 2025.
Applicable IRL (Q1 2026): 143.87
Reference IRL (Q1 2025): 140.98
New rent = 750 × (143.87 / 140.98)
New rent = €765.37 / month
Need the figure for your own numbers? Use the IRL rent increase calculator then carry the result into the letter, or let FacturZen generate both at once.
Letter template
[Landlord name and address]
[Tenant name and address]
[City], [date]
Subject: annual rent revision
Registered letter with acknowledgement of receipt
Dear Sir or Madam,
The lease we signed on [date] provides for the annual revision of the rent based on the change in the Rent Reference Index (IRL), pursuant to Article 17-1 of the Act of 6 July 1989.
The reference IRL is that of [quarter] (value […]). The IRL applicable at the revision date is that of [quarter] (value […]). Your new rent is therefore €[…] excluding charges, per the calculation: current rent × applicable IRL ÷ reference IRL.
Please pay this new rent from [effective date].
Yours faithfully,
[Landlord signature]
Generate the letter automatically
FacturZen pre-fills this letter from your lease data: identities, addresses, signing date, chosen IRL values, the calculation and the new rent. It also checks eligibility — including the legal freeze on DPE F and G properties — updates the lease rent if you choose, and can email the PDF to the tenant. The calculation method is the one detailed in our IRL index article.
Conclusion
A correct calculation is worthless without a written, complete and dated notification. A compliant letter, sent on time and by registered mail, turns a theoretical right into rent you actually collect — with no dispute risk.
Try FacturZen free for 14 days — IRL calculation, a pre-filled revision letter, and lease update in a few clicks.
Frequently asked questions
Is a written letter mandatory to revise the rent in France?
In practice, yes. Rent revision is not automatic: until the landlord notifies the tenant in writing, only the old rent is due. A written, dated notification is essential to make the revision enforceable and to prove the date you claimed it.
Do I have to send it by registered mail?
The law does not strictly require registered mail, but it is strongly advised. If the tenant disputes the increase, the acknowledgement of receipt is the only indisputable proof of the notification date and content. A plain email or letter is legally weak.
What is the deadline to claim the revision?
The landlord has one year from the revision date set in the lease to notify the increase. After that, the revision for that year is permanently lost — it is not retroactive beyond the notification and cannot be recovered the following year.
Can the revision be retroactive?
No. The new rent applies from the notification date, not from the lease anniversary if it has already passed. Notifying quickly after the anniversary date avoids losing several revised monthly payments.
What must the letter contain?
The lease and its signing date, the indexation clause invoked (Article 17-1 of the Act of 6 July 1989), the reference IRL and the applicable IRL with their quarters, the calculation, the new rent excluding charges, and the effective date. FacturZen generates a pre-filled letter with all of these.
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