Commercial rent indexation calculator
Compute an indexed French commercial rent from your two index values, the one in your lease and the latest published quarter. The tool applies the indexation, caps it when a symmetrical ILC tunnel clause exists, and tells you which index the law attaches to your lease.
Compute the revised rent from the reference index and the revision index.
Cap the variation when the lease carries a symmetrical ILC tunnel clause.
Check that the index written into the lease is the one the law retains.
The arithmetic is trivial, the difficulty is elsewhere
The calculation is one line: current rent multiplied by the ratio of the two index values. What is actually argued is the index retained, the period compared and the drafting of the clause. That is where this tool stops you, rather than letting you compute on an index that has no business being in your lease.
ILC, ILAT or ICC
For a lease signed or renewed since 1 September 2014, the capping of the three-yearly review and of the renewed rent is measured on the ILC or the ILAT, never on the ICC.
- ILC: commercial and craft activities.
- ILAT: other tertiary activities, including liberal professions.
- The activity carried on in the premises decides, not the floor area or the rent.
Tunnel clause, since 28 May 2026
Article L. 145-38-1 of the French commercial code, created by law no. 2026-403 of 26 May 2026, expressly allows a clause capping the annual ILC variation used for the rent review.
- The cap must bear on the ILC.
- It must work in the same proportions upwards and downwards.
- A clause that caps only increases is deemed unwritten.
Why no index series is stored here
INSEE publishes a new quarter every three months. A series frozen into a tool goes stale silently, and a wrong index produces a wrong rent that nobody notices.
- You enter both values: they are in your lease and in the INSEE publication.
- Reference for the quarter published on 23 September 2026: ILC 137.16, ILAT 138.01, ICC 2,103.
- The full series and their history stay on our construction cost index page.
Before applying a revision
A correct calculation on a fragile clause is worthless: the indexation clause is the first document to re-read.
- Check which index is stipulated, and whether it matches the activity actually carried on.
- Check that the period between the two index values is the one the clause provides for.
- Check that any cap works both upwards and downwards.
- Keep the INSEE publication for the quarter retained: it is what counts if the figure is challenged.
What we look at first
On a rent review, the calculation comes last. We start with the clause: the index stipulated, the reference period, the symmetry of any cap and the effective date. A clause comparing two periods of different lengths, or capping only increases, weakens the whole indexation, including the years already applied.
The underestimated risk
Applying indexation on the wrong index for several years. The correction then runs both ways, with a catch-up or a refund, and a limitation-period discussion neither party had anticipated.
FAQ on French commercial rent indexation
Which index applies to a French commercial lease in 2026?
For a lease signed or renewed since 1 September 2014, capping is measured on the ILC for commercial and craft activities, and on the ILAT for other tertiary activities including liberal professions. The ICC no longer appears there since the law of 18 June 2014, although it remains a lawful escalation index in an agreement relating to a built property.
How is an indexed rent computed?
Revised rent = current rent multiplied by the revision index divided by the reference index. Both values are read from the lease and from the INSEE publication for the relevant quarter. The result then applies according to the clause, on the date it provides for.
What is a tunnel clause, and is it lawful?
It caps the annual variation of the index, for instance between minus 3% and plus 3%. Since 28 May 2026, article L. 145-38-1 of the commercial code expressly allows it for the ILC, provided it works in the same proportions upwards and downwards. A clause capping only increases is deemed unwritten.
Does the tool replace reading the lease?
No, deliberately. It applies an indexation and flags the rules that govern the choice of index, but the exact drafting of your clause decides the period retained, the effective date and how the cap works. A badly drafted clause can be deemed unwritten, in which case there is no indexation at all.
Sources
Rules up to date as at 14 August 2026. Index values are not stored in the tool: the latest published quarter as at 23 October 2026 is Q2 2026, published on 23 September 2026; the next one is announced for late December 2026.
Going further
Need an indexation clause reviewed?
We re-read the clause, recompute the revisions already applied and quantify the gap, before any discussion with the landlord or the tenant.