Summary: rent increases in 2026 after the end of the 25% cap, calculating the CPI limit, the five-year rent determination lawsuit, the equity reduction and the mediation process. Turkish tenancy law entered a new phase when the 25% cap on rent increases for residential leases was lifted on 1 July 2024. As of 2026, the dispute that landlords and tenants face most often is bringing the rent in line with market rates. With high inflation, setting the rent is not only a calculation: it is a legal process that requires close attention to statutory time limits and to the Court of Cassation's equity criteria. This article explains, based on the current 2026 CPI rates, the five-year rent determination lawsuit, rent adaptation disputes and the new cost items at the mandatory mediation stage.
1. The statutory limit on rent increases: the CPI rule
Under Article 344 of the Turkish Code of Obligations No. 6098 (TBK), the increase rate the parties agree in the lease cannot exceed the change in the twelve-month average of the consumer price index (CPI, TÜFE) over the previous lease year.
1.1 The CPI in 2026
The twelve-month average CPI announced in January 2026 is about 34.88%. This is the statutory ceiling for tenants whose lease renews.
- Commercial premises: the 25% cap never applied to commercial premises; their increase has always been limited to the twelve-month average CPI.
- Residential premises: there is no longer a 25% cap. An increase imposed above the CPI rate is legally invalid (TBK art. 344/1).
1.2 If the lease sets no rate
If the lease contains no clause on increases and the parties cannot agree, the judge sets the rent in line with equity, taking into account the condition of the leased property (TBK art. 344/2). Even then, the increase cannot exceed the CPI rate.
2. The five-year rule and the rent determination lawsuit
One of the most important institutions of tenancy law is the rent determination lawsuit (TBK art. 344/3). It allows the rent to be balanced not only against the index (CPI) but also against comparable rent increases in the area.
2.1 Conditions for setting the rent by comparable rents
- Five-year period: five years must have passed since the start of the lease; this determination can then be requested again at the end of every further five years. A rent determination lawsuit can also be filed before five years have passed (TBK art. 345), but in that case the new rent is set within the CPI limit, not by comparable rents.
- Mediation as a prec since 1 September 2023, applying to a mediator is mandatory before a rent determination lawsuit is filed.
2.2 Setting the rent (market value)
Under art. 344/3, the court takes the following criteria into account when setting the rent:
- CPI rate: the increase in the index.
- Condition of the property: upkeep of the flat, its frontage, whether there is a lift, and similar features.
- Comparable rents: the rents of similar properties in the area that have recently been let.
- Equity reduction: after an expert has established the market rent, the court reduces that figure by between 10% and 20% because the tenant is an existing tenant. This is called the equity reduction.
3. Rent adaptation lawsuit (without waiting five years)
Sometimes the market changes so sharply that waiting five years becomes unbearable for one of the parties. In that case an adaptation lawsuit for excessive hardship of performance can be filed under TBK art. 138. | Criterion | Rent determination lawsuit | Rent adaptation lawsuit | | --- | --- | --- | | Time condition | At least five years must have passed for setting the rent by comparable rents | No time condition | | Ground | Expiry of the period and the gap to market rent | An extraordinary, unforeseeable change | | Burden of proof | Comparable rents | Excessive hardship of performance (crisis, war and similar events) | | Outcome | The rent for the new period is set | The lease is adapted to current conditions | Important note: the Court of Cassation regards ordinary inflation as foreseeable and tends to reject adaptation lawsuits. However, extreme jumps in exchange rates or sudden zoning changes in the area may be a ground for adaptation.
4. The notice period and the effect of the lawsuit (TBK art. 345)
A rent determination lawsuit can be filed at any time. The lease period from which the rent set by the court applies depends on when the lawsuit is filed and when written notice is given.
- 30 days before the period begins: if the lawsuit is filed at least 30 days before the new lease period begins, or if the landlord gives the tenant written notice within that time and files the lawsuit by the end of the new period, the rent set applies from the start of that new period.
- If the lease provides for an increase: if the lease contains a clause that the rent will be increased, a judgment in a lawsuit filed by the end of the new period also applies from the start of that period.
- If the time limit is missed: if these conditions are not met, the new rent set by the court applies only from the following lease period.
5. Mediation and litigation costs in 2026
5.1 The 2026 mediation tariff
If agreement is reached at mediation, the fee is calculated at 6% of the annual rent difference established, shared equally by the parties. For 2026, the mediation fee starts from a minimum of TRY 9,000.
5.2 Court fees and expert costs
- Court fee: in rent determination lawsuits the court fee is proportional. It is charged at 68.31 per thousand of the rent difference claimed (the amount for one year).
- Expert: the court usually obtains a report from a real estate valuation expert and a legal expert (costs in 2026 are around TRY 4,000 to 6,000).
6. Frequently asked questions
Can I file a lawsuit for the market rent before five years have passed?
No. TBK art. 344/3 expressly requires five years. Before five years have passed, the landlord can only increase the rent by the CPI rate. If the tenant does not pay this increase, an eviction process for underpaid rent may be started, but the market rent cannot be set.
What is the equity reduction, and why does the judge make it?
According to the settled case law of the Court of Cassation's Assembly of Civil Chambers, the tenant is an existing tenant who pays no estate agent's commission, knows the property and pays regularly, so equity requires a reduction of 10% to 20% from the rent a new tenant would pay on the market.
How much should the tenant pay while the lawsuit is pending?
While the lawsuit continues, the tenant should keep paying with at least the statutory CPI increase. When the lawsuit ends, the difference set by the court (for example, a difference covering the previous ten months) is collected in one sum together with interest.
Is there a 25% cap on commercial rents?
No. The 25% cap never applied to commercial rents. Commercial premises have always been limited to the twelve-month average CPI.
7. Conclusion and legal notice
Rent increase disputes are one of the areas where the right of property and the principle of the social state collide most strongly. Under 2026 market conditions, missing the notice period (the 30-day rule) can delay by a year the landlord's right to have the increase applied from the start of the period. Likewise, tenants who do not pay even the minimum CPI increase because "the lawsuit will take long anyway" expose themselves directly to the risk of an eviction lawsuit. Working with a tenancy law lawyer, so that the process runs without errors, the comparable flats in expert reports are analysed correctly and the right strategy is followed at mediation, helps reduce the risk of lost time and lost rights. Legal notice: this article is for general information and is not legal advice. Every case has its own facts. Please consult a lawyer about your own situation.