Complete Guide to CPI in Rental Contracts 2026

The Consumer Price Index has been for decades the main reference for updating rental prices in Spain, allowing landlords to adjust prices according to cost of living evolution. However, recent years have brought significant changes to the regulatory framework that every landlord and tenant must know to correctly exercise their rights.

Understanding the CPI and its alternatives

The general CPI measures price variation of a representative basket of goods and services consumed by an average Spanish family. This measurement includes volatile products like energy and fresh food, which can cause significant fluctuations from one month to another. The underlying CPI excludes these volatile elements, offering a more stable measure of structural inflation.

From 2025, legislators introduced the Competitiveness Guarantee Index as the recommended reference for rental contracts. This index, which cannot exceed two percent annually nor be below zero in case of deflation, provides greater predictability for both landlords and tenants. Its calculation is based on a moving average of underlying inflation, eliminating sharp fluctuations.

The current legal framework

The Urban Leases Law establishes that rent updates can only be made when at least one year of contract validity has passed, must be expressly agreed in the document, are applied using the index agreed between parties, and require prior notification to the tenant.

Recent years have seen the imposition of extraordinary limits on increases. In 2022 and 2023 the cap was set at two percent, in 2024 it rose to three percent, and from 2025 the new IGC framework or freely agreed index applies for small landlords, while large landlords—those with more than ten properties in stressed areas—maintain the three percent limit in any case.

How to calculate the update

The calculation follows a simple formula: the new rent results from multiplying the current rent by one plus the index variation divided by one hundred. For example, with a rent of 850 euros and an interannual CPI of 3.5 percent, the calculation would give 879.75 euros. However, if the current legal limit is three percent, only an increase up to 875.50 euros could be applied.

When the index is negative, rent can effectively be reduced. A rent of 900 euros with a CPI of minus 0.5 percent would result in 895.50 euros. However, many contracts include "no reduction" clauses that prevent decreases even if the index is negative.

Example	Current rent	Index	Limit	New rent
High CPI	850€	3.5%	3%	875.50€
Normal IGC	750€	1.8%	-	763.50€
Negative CPI	900€	-0.5%	-	895.50€

The update clause in the contract

Without a specific clause authorizing the update, the landlord has no right to modify rent during the lease term. A well-drafted clause must specify the review periodicity—normally annual coinciding with the contract anniversary—, the applicable reference index, the specific month that will serve for calculation, the notification procedure, and an alternative index in case the main one stops being published.

Standard clause: The rent will be updated annually on the date of each contract anniversary, applying the percentage variation of the Competitiveness Guarantee Index published by the National Statistics Institute, corresponding to the month immediately prior to the update date.

Formal notification to the tenant

The update notification must be in writing, including the communication date, contract identification with its date and property address, current rent, index applied with its exact value, calculated new rent, and the date from which it will be effective. It's recommended to send this communication at least thirty days in advance to give the tenant time to adjust their forecasts.

If the landlord doesn't notify in time, the new rent will only take effect from the notification date, without the possibility of applying retroactivity. Missing a year's deadline means permanently losing that increase.

Special situations

Contracts that don't include an update clause don't allow modifying rent, unless a new agreement is reached with the tenant. The rent remains unchanged throughout the contract term.

In areas declared as stressed, stricter limits than general ones may apply, and even specific reference indices established by regional regulations. It's advisable to check the particular situation of each location.

The first year of the contract doesn't allow any update. Regardless of when the document was signed, the first review can only be applied upon completing twelve months from the start. At the beginning of each extension, parties have the opportunity to review conditions, including the applicable reference index and deposit update.

The tenant's right to challenge

If the tenant considers that the update doesn't comply with law, they can challenge it when there's no update clause in the contract, the applicable legal limit is exceeded, the calculation contains errors, or proper notification hasn't been given. The procedure begins with written communication of the discrepancy, followed by a request for detailed justification. If disagreement persists, mediation offers a resolution path before going to courts as a last resort.

Tools like Inquly automate this entire process: alerts that warn when the update date approaches, automatic calculation with updated official indices, generation of personalized notifications compliant with regulations, historical record of all applied updates, automatic verification that legal limits are respected, and storage of all supporting documentation. Automation eliminates errors and ensures strict compliance with deadlines and procedures.