Most disputes between landlords and tenants at renewal come down to one confusion: which CPI figure?
This guide sets out where to find the right rate, how to apply it, and what is invalid.
The legal cap: 12-month average CPI
Under the Turkish Code of Obligations, the maximum rent increase is the rate of change in the consumer price index according to twelve-month averages.
Every word in that definition matters:
- Twelve-month average — the average over the past year.
- Not annual inflation. Change against the same month last year is a different, usually higher, figure.
- Not monthly inflation. Change against the previous month is different again.
TÜİK publishes all three together every month. Only the first applies to rent increases.
Why there is no number in this article
Because the rate changes every month. A figure printed here would be wrong within one — and an increase applied on a wrong figure is invalid as to the excess.
To find the correct rate:
- Look at TÜİK's CPI bulletin (published at the start of each month).
- Take the line "rate of change according to twelve-month averages".
- Use the value published in the month before your agreement renews.
The third step is the most skipped. For an agreement renewing in September, the rate to use is the one published in August.
The calculation
Increase = Current rent × (Rate ÷ 100)
New rent = Current rent + Increase
Or in one step:
New rent = Current rent × (1 + Rate ÷ 100)
Example (assuming a rate of 30%): Current rent ₺20,000 → 20,000 × 1.30 = ₺26,000
Find the actual rate with the three steps above; the 30% here only illustrates the formula.
The five-year rule
When a tenancy passes five years, the position changes. At the renewal at the end of the fifth year the increase is no longer capped by CPI; either party may apply to court to have the rent redetermined on a fair and equitable basis.
Most long-term tenants do not know about this clause, and it works both ways:
- For a landlord: a chance to update a rent that has fallen behind the market over five years.
- For a tenant: a chance to seek a reduction if the market has fallen — rarely invoked, but it is your right.
The five-year rule is not automatic; it requires an application to court.
Six common mistakes
1. Using the wrong CPI line. An increase based on annual inflation usually exceeds the legal cap, and the excess is invalid.
2. Using the wrong month's rate. It is the rate published in the preceding month, not the renewal month itself.
3. Applying a fixed contractual rate above the cap. Even if the agreement says "60% annually", anything above the legal cap is invalid. A contract cannot override the statute.
4. Assuming no increase is possible without a clause. If the agreement is silent, the statutory cap applies and an increase can still be made.
5. Increasing mid-term. The increase falls due when the rental year completes. An increase demanded mid-year is not binding.
6. Not giving written notice. The demand should be made in writing; a verbal one creates an evidential problem later.
Commercial tenancies
The same twelve-month average CPI cap applies to commercial leases. In practice, though, bargaining power and freedom of contract play out differently; long commercial leases sometimes use foreign-currency or turnover-based arrangements.
For detail on the commercial side, see our commercial letting guide.
Practical advice
For landlords: give notice in writing a reasonable time before the renewal date, stating the source of the rate ("TÜİK, month X, change by twelve-month averages: Y%"). A notice that cites its source is not argued with.
For tenants: verify the demanded rate against the TÜİK bulletin. If it exceeds the legal cap you are not obliged to pay the excess — but say so in writing and cite the source.
When both sides look at the same figure, this stops being a dispute. Almost every disagreement here comes from the two parties reading different lines of the same table.