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Rent update calculator for Spain: CPI or IRAV
Enter the rent, the month the lease year is completed and the agreed index. The calculator applies the latest INE figure and the caps of Spain's Urban Leases Act, and drafts the notice for the tenant.
- IRAV for September 2026: 2.54%
- LAU caps applied
- No sign-up, no data sent
Work out the new rent
INE data up to September 2026. Results update as you type.
In FixrOS the system calculates the update and the tenant gets the notice in their portal
How to calculate a rent increase, step by step
The formula is simple: new rent = current rent × (1 + percentage / 100). What changes from one lease to another is which percentage can be applied. To find out, you need to answer four questions, which are the ones the calculator asks:
- Does the lease provide for an update? Without a clause, the rent is not updated (art. 18.1 LAU). If there is one but it names no index, the IRAV is used.
- Is it a home or commercial premises? For housing, the rise cannot exceed the IRAV result. For shops and offices, the agreement rules (art. 4.3 LAU).
- When is the lease year completed? You use the latest index published by INE on that day. Also, if the anniversary falls between 8 October 2026 and 31 December 2027, for housing and without a new agreement the maximum rise is 2%.
- Which index does the lease name? IRAV or headline CPI. If a residential lease says CPI and CPI is higher than the IRAV, the IRAV applies.
Which index month to use
Article 18.1 of the LAU takes as reference month the one matching the latest index published on the lease update date. INE usually publishes the previous month's figure around the middle of each month. So for an anniversary on the 1st, you normally use the index from two months earlier: for 1 December, October's. If the anniversary falls late in the month, the previous month's may already be out. The calculator picks the one from two months earlier by default and lets you change it.
What rise can be applied in each case
| Case | What applies | Rule |
|---|---|---|
| Home, no update clause | No update | Art. 18.1 LAU |
| Home, clause naming no index | Annual change in the IRAV | Art. 18.1 LAU |
| Home, CPI clause | CPI, without exceeding the IRAV | Art. 18.1 LAU |
| Home leased before Law 12/2023 | The agreed index, with the same IRAV cap | 4th TP of Law 12/2023 (as worded by RDL 29/2026) |
| Home with anniversary between 08/10/2026 and 31/12/2027 | New agreement or, without one, 2% at most. Nothing if the rent is above the reference price index | 6th FP RDL 29/2026 |
| Shop, office or other use | What the lease says | Art. 4.3 LAU |
Sources: LAU, consolidated text and Royal Decree-law 29/2026 (BOE).
How to notify the tenant of the update
Article 18.2 of the LAU sets the procedure: the updated rent is payable from the month after the interested party notifies the other in writing, stating the percentage applied and enclosing, if the tenant requires it, the INE certificate. A note on the previous month's receipt is also valid notice.
The calculator produces a template with those elements: the anniversary, the index and reference month, the percentage applied, the old and new rent, and the offer of the INE certificate. Fill in the details in square brackets and send it by a method that proves receipt, or to the email address agreed in the lease if there is one (art. 4.6 LAU).
Common mistakes when updating rent
- Applying CPI to a residential lease when the IRAV is lower.
- Forgetting the 2% cap for anniversaries between 8 October 2026 and 31 December 2027 when there is no new agreement.
- Using the index for the anniversary month, which is not published yet, instead of the latest available.
- Charging the new rent retroactively: it is only payable from the month after notice.
- Updating recharged costs with the same index: they follow their own rules (art. 20 LAU).
If you manage many leases
With ten leases you can do it by hand; with a hundred, the risk of getting the index or month wrong is real. In the FixrOS Portfolio module, the system spots upcoming anniversaries, calculates the CPI or IRAV update with the INE index and proposes it; the manager confirms it, the tenant gets the notice in their portal and the following rent bills go out with the new rent.
Frequently asked questions
How is a rent increase calculated with CPI?
Multiply the rent by the annual CPI change for the reference month and add it to the current rent. With €800 and CPI at 3%, the new rent is €824. For housing, the result cannot exceed the one obtained with the IRAV.
How much can a residential rent go up?
At most, the result of applying the IRAV for the reference month (art. 18.1 LAU). And if the anniversary falls between 8 October 2026 and 31 December 2027, without a new agreement with the tenant, 2% at most.
Can I update the rent if the lease says nothing?
No. Without an express agreement, no rent update applies (art. 18.1 LAU).
From when is the updated rent payable?
From the month after written notice is given to the tenant, stating the percentage applied (art. 18.2 LAU). A note on the previous month's receipt is valid.
Can the rent go down if the index is negative?
If the lease updates by an index and that index is negative, the update is negative too and the rent goes down. The calculator shows it and flags it.
Is the data I enter stored?
No. The calculation runs in your browser and nothing is sent to any server.
Information checked on 18 October 2026 against Law 29/1994 on Urban Leases, Royal Decree-law 29/2026 and INE data. The decree-law must be ratified by the Spanish Congress (art. 86 of the Constitution); an earlier one with the same change, 26/2026, was repealed. The calculator is a guide: check your lease and the rules in force. This is not a substitute for professional advice.
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