IRL Index 2026: How to Adjust Rent on a French Lease (Method + Example)

What is the IRL index and who can use it?

The IRL (Indice de Référence des Loyers, "rent reference index") is the official index published every quarter by INSEE, the French national statistics office. Its sole purpose is to adjust rents on residential leases, accounting for inflation excluding tobacco and excluding rents themselves. It is the only legally accepted reference for residential leases governed by the loi 89-462 of 6 July 1989.

Three conditions must be met before you can apply it:

• A residential lease (primary residence, furnished or unfurnished). Commercial and professional leases follow different indexes (ILC, ILAT).
• An indexation clause already in the lease. If the clause is missing or poorly drafted, you cannot revise the rent during the lease — full stop.
• The lease anniversary date. An adjustment is allowed once per year only, on the date set in the clause — typically the move-in date.

The calculation formula

The formula is fixed by article 17-1 of the loi 89-462:

The "New IRL" is the IRL value for the quarter immediately preceding the lease anniversary date. The "Old IRL" is the IRL value for the same quarter one year earlier — i.e. the index already recorded in the lease at the previous revision (or at signature). Any other pair of indexes makes the adjustment legally challengeable.

Worked example

Let's run a concrete case. You rent out an apartment for €750 per month (excluding charges). The lease was signed on 1 March 2024, so the anniversary date falls on 1 March 2026. The reference IRL is the one for the quarter just before that date — Q4 2025.

The monthly increase is €17.99, an adjustment of +2.40 %. Over a full year, that's roughly €216 of additional rent — money you'd have left on the table by forgetting the revision. Take Marie, an English landlord with a T3 in Lyon rented at €780. She skipped the IRL revision three years running because "the formula looked fiddly". Compounded losses by year four: just over €960. A fiddly formula it isn't.

Notifying the tenant correctly

The adjustment is not automatic: it requires written notice to the tenant (email, plain letter, or registered letter). If you fail to notify within the year following the anniversary date, the right to adjust for that year is lost — there is no retroactive recovery. Below is a minimal, legally compliant template:

How to automate this adjustment annually

The IRL revision is, by design, a yearly task. Isolated. Easy to forget. Almost impossible to track cleanly when you juggle several units with different anniversary dates from another time zone. It's exactly the kind of recurring operation a property management software should handle for you.

With FacturZen, you configure the indexation clause once when you create the lease (anniversary date, initial IRL value). As each anniversary approaches, the application pulls the correct reference quarter, runs the formula, checks the 3.5 % cap and the DPE class, then generates a notification letter ready to send to the tenant. The new rent is then propagated without further intervention to the automatic rent receipts issued every month. Everything is bundled in the €7-per-month plan.

Conclusion: stop leaving IRL revisions to chance

The annual IRL rent adjustment is neither complex nor optional for a landlord who wants to preserve the yield of a French rental. The formula is one line long, the legal framework is stable in 2026, and the tools exist to make sure you never think about it again. Over 10 years, the gap between a landlord who revises every year and one who forgets adds up to several thousand euros per unit.