Every year, as the renewal month approaches, landlords ask the same question: "How much can I raise the rent this year?" The answer hides in a single number — and which number that is gets mixed up constantly. It is not annual inflation, and it is certainly not monthly inflation. What the law looks for is the change in CPI according to twelve-month averages.
This guide walks through where to find the correct rate, how to run the calculation, and why the 25% cap era of 2022–2024 is still being felt in Istanbul rents today. If you own from abroad and a manager handles your renewals, this is also the arithmetic they should be showing you every year.
The legal basis: TBK 344 and the twelve-month average
Article 344 of the Turkish Code of Obligations sets the upper limit for renewal-period increases in residential and roofed workplace tenancies: the parties may agree an increase freely, provided it does not exceed the change in the consumer price index according to twelve-month averages for the previous rental year.
Three points worth underlining:
- This is a ceiling. Agreeing a lower increase is always possible.
- Even if the contract states a higher rate, the legal cap is what applies; the excess cannot be demanded.
- If the contract has no increase clause at all and the parties cannot agree, a judge sets the rent equitably — again without exceeding this cap.
Which rate is the right one? Reading the TurkStat data
TurkStat publishes the previous month's inflation figures at the start of each month, and the table shows two different rates:
| Rate | What it means | Used for rent increases? |
|---|---|---|
| Annual change | Total price growth over the last 12 months | No |
| Change on twelve-month averages | The average of the last 12 months against the average of the previous 12 | Yes |
In the June 2026 release, for example, annual CPI was announced at 32.11% — but the legal cap applying to contracts renewing in July 2026 was the twelve-month average: 32.03%. Even when the two look close, using the right one matters; in periods when inflation is falling or rising quickly, the gap between them opens up seriously.
Which month's data do you use? Whatever month your contract renews in, the applicable rate is the published twelve-month average for the month before it. An August renewal uses the July figure (published in early August); a July renewal uses June's, and so on.
The calculation, step by step
The formula is simple:
New rent = current rent × (1 + rate / 100)
Take a contract renewing in July 2026:
- Current monthly rent: TL 20,000
- Applicable rate: 32.03%
- Increase: 20,000 × 0.3203 = TL 6,406
- New rent: TL 26,406
On an annual basis, the tenant's total payment rises from TL 240,000 to TL 316,872. Rounding is purely a courtesy between the parties: if the legal cap lands at TL 26,406 you cannot ask TL 26,500 — but you can agree on TL 26,400.
If you would rather not do this by hand, our rent increase calculator applies the current rate and gives the result in seconds.
The 25% cap era and its long shadow
A temporary measure introduced in June 2022 capped residential rent increases at 25%, regardless of CPI. Extended twice, the cap ended in July 2024; contracts renewing on or after 2 July 2024 returned to the twelve-month average CPI rule.
While the cap held, inflation ran in the 60–80% band and increases stayed at 25% — so a large share of apartments let in that period ended up with rents visibly below market. This is the main reason you see rent differences of up to double between two similar apartments in the same Istanbul building today.
The practical consequence for a landlord: a CPI increase on its own will not carry a lagging rent back to market level — it only preserves the purchasing power of the existing rent. Closing that gap has a legal route of its own, which brings us to the five-year rule.
After five years: the rent determination lawsuit
Once a tenancy has completed five years, either party may file a rent determination lawsuit to have the rent set afresh. In that case the judge is not bound by the CPI ceiling; the new rent is set with regard to comparable rents, the condition of the property and equity. In practice, courts work from comparable evidence and apply a fairness discount to reach the figure.
Because this route is unavailable before the five-year mark, tracking contract anniversaries matters — especially for rents that fell behind during the cap era. For owners abroad this is exactly the kind of deadline a manager should be watching; our guide to property management for remote owners covers how renewals and these milestones are handled at a distance. Before going anywhere near a court, know your apartment's realistic market rent — a claim without comparable evidence wastes everyone's time; a free valuation is the place to start.
The three mistakes we see most often
Using the wrong rate. Running the numbers with the headline annual inflation figure is the most common error. The law asks for the twelve-month average.
Using the wrong month's data. The basis is the published figure for the month before the renewal — not the renewal month itself. A contract renewing in October uses September's data.
Claiming the increase retroactively. The increase applies from the month the new rental year begins. Even if you notified late, demanding back-payment for past months usually just creates a dispute; written notice a few weeks before the renewal date is the clean path.
How to give notice — and what if the tenant refuses?
The law does not prescribe a rigid form for the increase notice, but proof is everything. The healthiest method is written notice at least 15–30 days before the renewal date: a notary notice is the strongest, while registered mail — or even a dated message exchange with replies — works in practice. State the old rent, the applied rate and the new amount explicitly; vague wording like "I'm increasing by CPI" invites argument.
A tenant must accept an increase within the legal cap; a contractual increase clause operates automatically anyway. If they keep paying the old rent regardless, the difference counts as underpayment. The remedy is a written warning covering the shortfall — and a tenant who causes two justified warnings within one rental year opens the door to an eviction case, a process we walk through in evicting a tenant in Turkey. The same twelve-month average CPI cap applies to workplace tenancies; higher rates or alternative indexes written into a contract cannot exceed it.
One exception to note: where rent has been agreed in foreign currency (which has its own separate conditions), no increase at all can be applied before five years have passed — the CPI mechanism belongs to TL contracts.
Sitting down with the tenant
The legal cap is a right — but demanding the full cap every year is not always the most profitable strategy. Losing a reliable, punctual tenant over a few percentage points usually costs more than it earns once you price in a month or two of vacancy, refurbishment and the search for a new tenant. Conversely, if the rent has fallen far below market, even a full-cap increase may not be enough — that is when the five-year rule and comparable evidence belong on the table.
At Turc Global we strike this balance together with the owner at every renewal in the tenancies we manage. If your own renewal is approaching, check your legal ceiling with the calculator — and if you want to know your apartment's current market rent, we are one valuation request away.