If you're an Italian tenant or landlord, every year you face the same question: the ISTAT adjustment of the rent. How much does the rent go up? How is it calculated? Can the landlord apply it automatically? This complete guide explains the ISTAT adjustment mechanism, the applicable rates by contract type, and how to calculate it correctly with practical 2026 examples.
What Is the ISTAT Rent Adjustment
The ISTAT adjustment is the mechanism that updates the rent according to the change in the cost of living, measured by the consumer price index published by ISTAT (Italian National Institute of Statistics). The goal is to protect the landlord's purchasing power: if inflation is 2%, a €500 rent today is "worth" less next year. The adjustment compensates this loss of value.
The adjustment is not automatic: it must be provided for in the lease agreement and, in most cases, the landlord must formally notify the tenant.
The FOI Index: The Reference Parameter
The index used for rent adjustment is the FOI (Consumer Price Index for Households of Workers and Employees), excluding tobacco. ISTAT publishes it monthly on the Official Gazette and on its website. Warning: there are several ISTAT indices (NIC, IPCA, FOI). For rents, only the FOI excluding tobacco is used.
The FOI percentage change is calculated by comparing the index of the reference month with that of the same month of the previous year. Example: if the FOI of January 2026 is 120.5 and that of January 2025 was 118.2, the change is: (120.5 − 118.2) / 118.2 × 100 = 1.94%.
75% or 100%: Which Rate Applies?
The applicable ISTAT adjustment percentage depends on the contract type:
| Contract type | Applicable ISTAT rate | Legal reference |
|---|---|---|
| Free 4+4 contract | 75% of FOI change | Art. 32 L. 392/1978 |
| Concordato 3+2 contract | 75% of FOI change | Art. 32 L. 392/1978 |
| Transitional contract | 75% of FOI change | Art. 32 L. 392/1978 |
| Commercial 6+6 contract | 75% of FOI change | Art. 32 L. 392/1978 |
| Contract with specific clause | Up to 100% | Agreement between parties |
The general rule for residential leases is 75%. 100% can only be applied if the contract contains an explicit clause providing for full adjustment. Without any clause, no adjustment is possible.
Worked example with 75%
Current monthly rent: €700. Annual FOI change: 2.40%. Applicable rate: 75%.
- Applicable change: 2.40% × 75% = 1.80%
- Monthly increase: 700 × 1.80% = €12.60
- New rent: 700 + 12.60 = €712.60/month
- Annual increase: 12.60 × 12 = €151.20 extra per year
Worked example with 100%
Same rent and change, but with 100% clause: change 2.40% → increase €16.80/month → new rent €716.80/month. Annual increase: €201.60. The difference between 75% and 100% in this case is €50.40 per year.
4+4 vs 3+2 Contracts: Adjustment Differences
Free rent contract (4+4)
The rent is freely agreed between the parties. ISTAT adjustment at 75% applies annually from the second year. The landlord sets the initial rent without constraints, and the adjustment keeps it in line with inflation.
Concordato 3+2 contract
The rent is determined based on territorial agreements between landlord and tenant associations. The initial rent is generally lower than the free market, but the landlord enjoys significant tax benefits: 30% IRPEF taxable income reduction (or 10% cedolare secca), IMU reduced to 75% (Law 160/2019, art. 1, paragraph 760), reduced registration tax. Adjustment also at 75%, unless otherwise stipulated.
When and How the Adjustment Applies
The adjustment applies starting from the contract anniversary. If signed April 1, 2024, the first possible adjustment is from April 1, 2025. The FOI index to use is generally the latest available before the anniversary date.
Notification to the tenant
The landlord must notify the tenant of the adjustment request. The notification must be in writing (registered letter A/R, PEC, or simple letter), indicate the FOI index used, the applied percentage and the new amount. It takes effect from the month following receipt. Important: if the landlord doesn't notify, the tenant doesn't have to pay it spontaneously. However, the landlord can claim arrears for the last 5 years (limitation period).
Compound or Year-by-Year Calculation?
The adjustment is always calculated on last year's rent (already adjusted), not on the original. This generates a compound effect.
Example over 3 years with initial rent €600 and FOI changes of 2%, 1.5% and 2.5%:
- Year 2: 600 + (600 × 2% × 75%) = €609
- Year 3: 609 + (609 × 1.5% × 75%) = €615.85
- Year 4: 615.85 + (615.85 × 2.5% × 75%) = €627.40
Cedolare Secca and ISTAT Adjustment
A key point: those who choose the cedolare secca regime (fixed rate of 21% for free contracts or 10% for concordati) waive ISTAT adjustment for the entire duration of the option. This means that if the landlord opts for cedolare secca, the rent stays unchanged for the entire contract term (4 or 3 years + renewal). It's a choice to weigh: does the tax saving from cedolare secca offset the loss of ISTAT adjustment?
What If Inflation Is Negative
In case of deflation (negative FOI change), the rent should theoretically decrease. However, many contracts contain a clause providing for adjustment "only in case of positive change". Without such a clause, the landlord should reduce the rent. In Italy, deflation occurred significantly only in 2014–2016, with very small negative changes (around −0.1% / −0.5%).
Frequently Asked Questions
Is the ISTAT adjustment mandatory?
No, it's not mandatory. It's a landlord's right that must be actively exercised with a written notification to the tenant. If the landlord doesn't request it, the tenant doesn't have to pay it. It must also be included in the contract.
Can the tenant refuse the adjustment?
If the adjustment clause is in the contract and the landlord has correctly notified the rent adjustment with references to the ISTAT indices, the tenant cannot refuse. In case of dispute, the landlord can take legal action to obtain unpaid differences.
Where do I find the updated FOI index?
The FOI index is published monthly on the ISTAT website (www.istat.it) in the "Prices" section. It's generally available around the 15th of the month following the reference month.
Can I apply the ISTAT adjustment with cedolare secca?
No. Choosing cedolare secca means explicit waiver of ISTAT adjustment for the entire duration of the option. If the landlord wants to apply the adjustment, he must return to the IRPEF regime, which is possible at the annual expiration of the cedolare option.