Contesting a rent increase in France: IRL revision, rent caps and letter template

Quick answer

A rent increase is only lawful in specific cases: the annual revision provided by a lease clause and computed on the IRL index (article 17-1 of the law of 6 July 1989), an increase at renewal for a manifestly undervalued rent (6 months' notice, references required), or after agreed improvement works. In high-demand zones, rent control further caps the rent at the loyer de référence majoré. Increase off the rails? Contest in writing then by registered mail, claim the overpayment back (3-year limit) and refer the case to the free departmental conciliation commission before the judge.

1. The only lawful increases during the lease

• Annual IRL revision: possible only if the lease contains a revision clause. Formula: rent × (new IRL ÷ IRL of the same quarter the year before). The reference index is the one named in the lease, otherwise the last one published at signature.
• One-year limit: the landlord must apply the revision within one year of its due date; afterwards it is lost for the past and only applies going forward, from the request.
• Improvement works: a rent uplift requires a written agreement (clause or amendment).

In rent-controlled high-demand zones (Paris, Lille, Lyon, Bordeaux, Montpellier…), the rent cannot exceed the loyer de référence majoré set by prefectoral order; any rent supplement must be justified by exceptional features and can be contested within 3 months.

2. Increases at lease renewal

For a manifestly undervalued rent, the landlord may propose an increase at renewal:

• Notice at least 6 months before the end of the lease, with comparable reference rents (3 or 6 depending on the town).
• You may refuse or stay silent: with no agreement 4 months before the term, the landlord (or you) refers the case to the departmental conciliation commission, then the judge before the term — otherwise the lease renews on the previous conditions.
• An accepted increase applies in steps (sixths or thirds depending on its size).

3. Check before contesting

• Re-read the lease: revision clause? index and reference quarter?
• Redo the IRL calculation with the INSEE indices.
• High-demand zone? Compare with your area's capped reference rent.
• Gather rent receipts and written exchanges: they quantify the overpayment.

4. Contestation letter template

Subject: Contestation of the rent increase — dwelling at [address]

Dear Sir or Madam,

By letter of [date], you notified me of a rent increase to €[amount] from [date]. After verification, this increase does not comply:

[As applicable] the lease contains no revision clause; / the calculation does not respect article 17-1 of the law of 6 July 1989 (applicable IRL: [index], i.e. a revised rent of €[amount]); / the requested revision covers a period more than one year old; / the rent exceeds the applicable capped reference rent (€[amount]).

I therefore ask you to withdraw this increase and, where applicable, to refund the overpayment of €[amount] for the months of [period].

Failing regularisation within 15 days, I will refer the matter to the departmental conciliation commission.

Yours faithfully,

[Date — Signature]

To give your contestation a certain date, MaisonMail can print and dispatch your letter through an available registered service. Origin market, delivery times, tracking and the proof-of-receipt slip are confirmed before payment. See also: writing a formal notice.

5. Escalation if talks stall

1. Contestation by registered mail with your calculation and references.
2. Departmental conciliation commission: free, seized by letter; it issues an opinion and settles most rent cases.
3. Protection litigation judge: within 3 years for the overpayment; the judge cancels an irregular increase and orders the refund.
4. Keep paying the uncontested rent during proceedings: never put yourself in arrears.

6. Common mistakes

• Paying the increase without checking the clause and the IRL calculation.
• Accepting a retroactive catch-up beyond the one-year limit.
• Letting the 3-month window pass to contest a rent supplement in a capped zone.
• Withholding rent in retaliation: that makes you the defaulting party.
• Contesting orally: without a dated letter, no starting point for the refund.

---

In short: during the lease, only an IRL revision under a clause is possible, within one year and without retroactivity; at renewal, an increase requires references and 6 months' notice; in high-demand zones, caps top it all. Check the maths, contest by registered mail, claim overpayments back within 3 years, and let the conciliation commission then the judge decide if needed.