An annual increase in maintenance and default interest are different matters. An annual increase changes the monthly amount payable on the date set by the decision. Interest, by contrast, is calculated on a money debt that was not paid when due, from the starting point the law requires. For an accurate result, the operative part of the decision, the monthly due dates, the basis of the increase, the payment records and the statutory interest rate in force for each period must be read together. [1; 2]
As of October 14, 2026, there is also an important legislative change: the amendment that entered into force on July 31, 2026 tied statutory interest to the rediscount rate of the Central Bank of the Republic of Türkiye (TCMB). For this reason, in a maintenance calculation that also covers earlier periods, it is not correct to apply the former 24 percent rate to all dates. This article explains the calculation logic for Turkish lira (TL) maintenance claims; foreign-currency maintenance should be assessed separately. [2; 8; 9]
Which information should be taken from the decision before starting the calculation?
First, the monthly principal and the start date of maintenance are determined. Then the payment day, the time of the first increase and the index to which the increase is tied are identified. “Increases every year” and “increases every January” do not describe the same date pattern. If the judgment contains only a starting amount, the calculation should not be upgraded by choosing a CPI or PPI rate on one's own initiative; instead, the scope of the judgment and the increase request should be assessed. [1; 5]
If the text of the divorce protocol differs from the judgment approved by the court, it must be clarified which provision is binding for the calculation. A sentence in the protocol that has no clear connection to the judgment may create a dispute if it is applied automatically. The index preferred by the person performing the calculation does not replace the criterion set by the court.
| Information to take from the decision | Why is it needed? |
|---|---|
| Initial monthly amount | Shows the principal on which the increase is applied |
| Start date and due dates | Separates the period in which the debt arose from the delay |
| First increase date | Prevents the first year from being increased incorrectly |
| Index and comparison basis | Separates the year-on-year change from the average change |
| Interest provision | Prevents going beyond the express terms of the provision |
Are CPI (TÜFE), PPI (ÜFE) and the twelve-month average the same thing?
No. The name of the index matters as much as the period against which the change is measured. A change compared with the same month of the previous year, a change based on twelve-month averages and a ratio between two index values produce different calculations. The method stated in the decision must be followed. The presence of a “TÜFE” option in a calculation tool does not prove that the data entered matches the criterion in the decision. [6]
The Court of Cassation's approach to index calculation
In the decision of the 8th Civil Chamber of the Court of Cassation (Yargıtay 8. Hukuk Dairesi) dated December 23, 2015, numbered E.2015/17356, K.2015/23067, an index calculation in line with a judgment providing for a six-monthly increase was examined. At the request-for-correction stage (karar düzeltme), the earlier reversal was lifted and the judgment was affirmed on different reasoning. For this reason, the earlier reversal explanation in the text must not be used as if it were a final result. The lesson of the decision is to preserve the period and method set by the judgment; it does not mean that a six-monthly increase applies to all maintenance. [6]
Deciding on a request for an annual increase
In the decision of the 2nd Civil Chamber of the Court of Cassation (Yargıtay 2. Hukuk Dairesi) dated March 24, 2026, numbered E.2025/5610, K.2026/3072, the failure to decide, either positively or negatively, on a request for an annual increase was among the grounds for reversal. The decision does not say that every maintenance amount is increased automatically by the PPI rate by operation of law. It shows that the court must address the request and that the judgment must be clear. [5]
How is an annual increase calculated?
Where the judgment provides for a percentage-based annual increase, the basic operation is to multiply the amount in force by one plus the rate. The figures below are hypothetical rates chosen only to explain the method; they are not real Turkish Statistical Institute (TÜİK) data or the result of a particular file.
| Period | Hypothetical calculation | New monthly amount |
|---|---|---|
| Starting point | Amount set by the court | 10,000 TL |
| First increase | 10,000 × 1.20 | 12,000 TL |
| Second increase | 12,000 × 1.10 | 13,200 TL |
In this example, recalculating the second increase from the initial 10,000 TL leads to a shortfall of 200 TL per month. If the judgment sets a different calculation method, that method applies. In a file where index values must be compared as ratios, adding the percentage change again may count the same increase twice.
Rounding must also be recorded. Small differences that are rounded differently each month can create disputes over the calculation in the long run. The index bulletin used, the relevant month, the rate or index value and the result of the calculation should be kept in the file. In this way the opposing party and the expert can reproduce the calculation.
From which date does maintenance interest run?
Stating the start of interest in a single phrase, such as “the filing date” or “the date the decision became final”, is insufficient in most files. It is examined whether the judgment contains an express interest provision, what the nature of the debt is, and when the relevant installment became due. Future monthly payments that have not yet fallen due are not charged interest as overdue debt from the date of the first decision. [3; 4]
Accumulated maintenance differences
In the decision of the 12th Civil Chamber of the Court of Cassation (Yargıtay 12. Hukuk Dairesi) dated April 12, 2007, numbered E.2007/4303, K.2007/7101, accumulated maintenance differences for which the judgment specified no interest start date were examined. Without accepting that the obligor was in default in respect of these differences before the decision, interest was calculated from the decision date. This assessment must not be generalized into a rule that interest on every maintenance installment always starts from the decision date. [3]
Installments that fall due later
In the decision of the 2nd Civil Chamber of the Court of Cassation dated December 12, 2023, numbered E.2023/8000, K.2023/6132, the date on which installments fall due was emphasized for the start of interest on poverty maintenance (yoksulluk nafakası). The other grounds for reversal in that decision concern the amount of maintenance and procedure. In practical terms, for interest purposes the due dates of the installments must be separated, and not all monthly payments may be charged from a single finality date. [4]
The 2026 change: how is statutory interest now determined?
Article 1 of Law No. 3095, as amended by Law No. 7589, takes as its basis 80 percent of the short-term rediscount rate of the Central Bank of the Republic of Türkiye (TCMB) on December 31 of the previous year. If the difference between the June 30 rate and the previous December 31 rate is five points or more, 80 percent of the June 30 rate applies in the second half of the year. The amendment entered into force on July 31, 2026. [2; 8]
On the review date, the official TCMB table shows a rediscount rate of 38.75 percent from December 20, 2025. The 80 percent calculation under the law gives 38.75 × 0.80 = 31 percent. This result is the outcome of the October 14, 2026 check; it is not a promise of a fixed rate for future years. The official table and the effective date information must be checked again on the day of the calculation. [9]
The new rate does not convert all interest already accrued for the earlier period into 31 percent with retroactive effect. For the same principal, the interest period is split on the date the change takes effect, and the rate for the earlier period is determined under the regulation in force on that date. Because maintenance is not a commercial debt, it is not correct to choose the commercial advance interest rate simply because it is higher. [2; 8]
Worked example of late interest
To show only the arithmetic, let us assume that interest is due on a principal of 10,000 TL which is 30 days late, at simple interest of 31 percent per year, and that a 365-day year is used. The calculation 10,000 × 0.31 × 30 / 365 gives approximately 254.79 TL. This example does not determine the date on which the right to interest arose; the due date, the claim, the payment and the applicable day count must be verified separately.
Under Article 3 of Law No. 3095, compound interest may not, as a rule, be applied in statutory interest calculations. Adding the interest calculated each month to the principal and charging interest on it again the following month is not the same as the annual increase of maintenance. The effect of the increase on the principal and the calculation of late-payment interest must be kept in separate columns. [2]
How are underpayments and irregular payments handled?
Payment is first matched with the debt to which it relates. An explained bank transfer, an enforcement collection record and the payment notice made by the parties are assessed together. Because of the set-off rules in Articles 100–102 of the Turkish Code of Obligations (TBK), it must not be assumed that every incoming amount is deducted directly from that month's principal. Costs, interest and multiple debts may affect the result, and the explanation given for a payment also matters. [7]
In particular, where deductions are made from salary and a separate bank transfer has also been sent, the possibility of double collection must be checked. When the payment date is posted to the account, the amount concerned stops generating interest for later days. Where there is a dispute, a calculation prepared by one party is not accepted as final; a verifiable breakdown supported by the underlying documents is presented.
Conclusion
A maintenance calculation must answer three separate questions: how much principal arose in each month, how much of it has been paid, and what interest applied to the remaining portion between which dates? Keeping the increase condition in the decision, the current statutory interest system and payment set-offs apart reduces both excessive claims and under-collection. The date distinction is mandatory, especially in long-term calculations covering the change of July 31, 2026.
Related articles: Coercive Imprisonment for Unpaid Maintenance: Conditions, Service, Complaint Deadlines and Objection; Can Overpaid Maintenance Be Recovered? Action for Recovery, Refunds in Enforcement Files and Time Limits; Where and How Is a Maintenance Case Filed? Competent Court, Jurisdiction, Mediation and Legal Aid.
Frequently Asked Questions
Does maintenance increase automatically every year?
Whether the judgment or an applicable rule contains an annual increase condition is examined. The same index is not applied automatically in every file. [1; 5]
Can I use PPI instead of CPI?
The criterion chosen by the judgment cannot be changed at the preference of the person calculating. Where there is uncertainty, the legal interpretation and the necessary application route are assessed. [6]
Are the twelve-month average and the annual change the same?
No. They are different comparison methods. The data entered into the calculation must match the criterion in the judgment. [6]
Is the second year's increase made on the initial amount?
In an ordinary percentage-based cumulative increase, the amount in force is the base. However, if the judgment contains a different method, that method is followed.
Does interest on all monthly payments start on the date of finality?
No. The due dates of later monthly payments are separated, and the interest provision of the judgment is read separately. [4]
Does interest on a maintenance difference always run from the filing date?
No general rule can be laid down. For the difference claim explained in the 2007 decision, the decision date was taken as the basis. [3]
Is statutory interest in October 2026 24 percent?
On the review date, the rate calculated under the new system is 31 percent. The period before July 31, 2026 is not calculated retroactively at the same rate. [2; 8; 9]
Can an increase and interest be calculated together?
Yes, where the conditions are met: one concerns the monthly amount and the other concerns the delay. The same increase or payment must not be counted twice. [1; 2]
Is accruing interest added to the principal the following month?
The prohibition on compound interest must be observed in statutory interest calculations. Continuously adding interest to the principal differs from the annual increase of maintenance. [2]
Are cash payments taken into account in the calculation?
Proof of the payment and of the debt to which it relates is required. A signed receipt and other evidence are assessed together with the set-off rules. [7]
Sources and legal bases
- Turkish Civil Code No. 4721 (Türk Medeni Kanunu), Articles 176, 330, 365. <https://www.mevzuat.gov.tr/mevzuatmetin/1.5.4721.pdf>
- Law No. 3095 on Statutory Interest and Default Interest (3095 sayılı Kanuni Faiz ve Temerrüt Faizine İlişkin Kanun), Articles 1–3 and the schedule of entry into force. <https://www.mevzuat.gov.tr/mevzuatmetin/1.5.3095.pdf>
- Court of Cassation 12th Civil Chamber (Yargıtay 12. Hukuk Dairesi), April 12, 2007, E.2007/4303, K.2007/7101. <https://mevzuat.adalet.gov.tr/ictihat/73081700>
- Court of Cassation 2nd Civil Chamber, December 12, 2023, E.2023/8000, K.2023/6132. <https://mevzuat.adalet.gov.tr/ictihat/997189900>
- Court of Cassation 2nd Civil Chamber, March 24, 2026, E.2025/5610, K.2026/3072. <https://mevzuat.adalet.gov.tr/ictihat/1217785000>
- Court of Cassation 8th Civil Chamber, December 23, 2015, E.2015/17356, K.2015/23067. <https://mevzuat.adalet.gov.tr/ictihat/193003400>
- Turkish Code of Obligations No. 6098 (Türk Borçlar Kanunu), Articles 100–102, 117–121. <https://www.mevzuat.gov.tr/mevzuatmetin/1.5.6098.pdf>
- Law No. 7589, Articles 10 and 26; Official Gazette (Resmî Gazete), July 31, 2026. <https://www.resmigazete.gov.tr/eskiler/2026/07/20260731-1.htm>
- Central Bank of the Republic of Türkiye (TCMB), Rediscount and Advance Interest Rates (Reeskont ve Avans Faiz Oranları); accessed October 14, 2026. <https://www.tcmb.gov.tr/wps/wcm/connect/TR/TCMB%2BTR/Main%2BMenu/Temel%2BFaaliyetler/Para%2BPolitikasi/Reeskont%2Bve%2BAvans%2BFaiz%2BOranlari>