The use of equivalent (aftermarket) or sub-industry parts instead of original parts in vehicle repair after a traffic accident results in a concrete financial loss for vehicle owners. In this article, the “actual damage” principle, the legal nature of using original parts, insurance companies’ discount practices, and the Constitutional Court’s annulment decision on the matter are discussed in light of judicial decisions. For practical information on how to collect the underpaid amount, you can also refer to our article titled What is the Damage Difference Amount, How to Collect Underpaid Damage from Insurance?
The Principle of Actual Damage and the Obligation to Use Original Parts
In general, court decisions show that the principle of “actual damage” is fundamental in compensating for damages incurred during the operation of motor vehicles. According to this principle, it is considered a legal requirement that the repair necessary for the injured party to restore their vehicle to its pre-accident condition must be carried out entirely with original parts. In the judgment dated 18.09.2019, numbered 2018/828 E. and 2019/817 K., of the Istanbul 5th Civil Court of Commerce, with reference to the established precedents of the 17th Civil Chamber of the Court of Cassation, it was stated that “Actual damage can only be ensured by using entirely original parts in the repair of the vehicle.” Similarly, in the judgment dated 11.09.2025, numbered 2023/108 E. and 2025/1171 K., of the İzmir Regional Court of Justice 11th Civil Chamber, it was emphasized that the injured party cannot be expected to repair their vehicle with used or equivalent parts, and that actual damage can only be covered by the use of original parts.
Related content: Regarding the compensation being limited by the fault rate and the effect of fault determination on the process, you can review our article titled How is the Fault Rate Determined in Traffic Accidents?
Legal Nature of Using Equivalent Parts and Compensation Liability
Courts consider the use of equivalent or aftermarket parts instead of original parts in repairs as not fully compensating the actual damage. In the decision of Istanbul 14th Civil Court of Commerce dated 30.01.2023, numbered 2020/620 (Docket) and 2023/57 (Decision), it was stated that repairs made without using original parts are not in compliance with policy conditions and that this means the vehicle’s damage was not properly remedied. In this context, it was ruled that the difference in cost between original parts and equivalent parts must be compensated. In the decision of Samsun Civil Court of Commerce dated 14.09.2023, numbered 2022/1358 (Docket) and 2023/929 (Decision), it was also stated that the damaged party cannot be expected to accept repair with equivalent parts, and repair costs must be calculated based on original part prices.
Insurance Companies’ Discount and Rebate Practices
It is a common view in many decisions that discounts applied by insurance companies on spare part and labor costs through contracted services cannot be taken into account when calculating the actual damage incurred by the injured party. In the decision of İzmir Regional Court of Justice 11th Civil Chamber dated 09.04.2026, numbered 2023/1906 (Docket) and 2026/586 (Decision), it was ruled that discounts made due to agreements between the insurance company and the service do not reflect the actual damage, and the cost of damage must be determined without applying these discounts. In the file of Istanbul 5th Civil Court of Commerce, numbered 2018/840 (Docket) and 2019/829 (Decision), it was also stated that the insurer is obliged to compensate the actual damage pursuant to Article 1283 of the Turkish Commercial Code (TTK) no. 6762, and therefore, it is not correct to apply a discount based on fair market value.
Constitutional Court Decision and Legislation Assessment
In the decision of the Insurance Arbitration Commission dated 28.12.2023 and numbered 2023/452520, it was stated that after the annulment decision of the Constitutional Court numbered 2019/40 (Main) and 2020/40 (Decision), it is not possible to apply the “calculation method by discount and equivalent part” introduced by the general conditions of Article 90 of the Highway Traffic Law. This situation strengthens the legal basis of the principle of actual damage and the use of original parts.
Exceptional Circumstances and Burden of Proof
In some court decisions, it is observed that the request for the use of original parts is rejected or made conditional on proof. In the judgment of Kayseri 2nd Civil Court of Commerce dated 30.01.2026, numbered 2025/218 (Main) and 2026/104 (Decision), the claim for damage difference was rejected on the grounds that it could not be determined that an equivalent part was used instead of an original part in the repair, and the plaintiff did not provide evidence of having incurred expenses for an original part. Furthermore, in the judgment of Diyarbakır Civil Court of Commerce dated 05.11.2025, numbered 2024/737 (Main) and 2025/1093 (Decision), the case was dismissed after it was determined as a result of expert examination that the parts used in the repair were already original.
In Conclusion, Judicial Trend
The vast majority of the reviewed decisions (e.g., Istanbul 1st Commercial Court of First Instance 2025/12 E. , Istanbul 11th Commercial Court of First Instance 2021/836 E. , Bursa 3rd Commercial Court of First Instance 2023/868 E. , Gaziantep 2nd Commercial Court of First Instance 2022/426 E. etc.) consistently emphasize that the use of equivalent parts in vehicle repair is not lawful, that the actual damage can only be compensated with original parts, and that insurance companies must pay the damage amount based on original part values without any discount. Although data regarding the judgment of İzmir 3rd Commercial Court of First Instance dated 26.09.2024, numbered 2024/2 Docket and 2024/723 Decision, mentioned in the question, is stated to not be recorded in some of the reviewed documents (İzmir 1st Commercial Court of First Instance, Insurance Arbitration, İzmir Regional Court of Justice 11th Civil Chamber), the general legal approach shows parallelism with the content of this decision.
In addition to the original part damage difference, it should not be forgotten that different damage items such as vehicle deprivation (downtime) compensation and replacement vehicle cost for the period the vehicle remained in service due to the accident can also be claimed in the same file.
Frequently Asked Questions (FAQ)
What can I do if the insurance uses an equivalent part instead of an original part?
In cases where an equivalent or aftermarket part is used instead of an original part without the vehicle owner’s explicit consent, the price difference between the two parts can be claimed as “damage difference cost.” Court decisions acknowledge that the insurance company is responsible for this difference, based on the principle of full compensation (actual damage).
What does the “actual damage” principle mean?
Actual damage is the cost required for the injured party to restore their vehicle to its pre-accident condition. According to established case law, this is generally considered fully covered only when exclusively original parts are used in the repair and no discounts are applied.
Is the insurance company’s agreed-upon service discount deducted from the damage amount?
No. Discounts arising from agreements between the insurance company and the service provider are not taken into account in the damage calculation, as they do not reflect the actual damage incurred by the injured party. The damage amount should be determined based on market rates without applying these discounts.
Is the “equivalent part and discount” method in Article 90 of the KTK still applied?
Following the Constitutional Court’s annulment decision, the calculation method involving discounts and equivalent parts introduced by general conditions is no longer considered applicable. This also strengthens the legal basis for the actual damage principle and the use of original parts.
Can I claim the damage difference even if I don’t repair my vehicle or provide an invoice?
According to judicial decisions, the insurance company is responsible for the actual damage incurred by the vehicle, regardless of whether the vehicle has been physically repaired or an invoice has been submitted. However, in specific disputes, an expert report suitable for review and any repair documents, if available, can be crucial for proving the claim.
What procedure should I follow for the damage difference?
First, a written application is made to the insurance company; if no result is obtained, after the mandatory mediation process, a lawsuit can be filed in the Civil Court of Commerce or an application can be made to the Insurance Arbitration Commission. Since a definitive decision rendered in one of these avenues is binding on the other, the choice of path carries strategic importance.
Why is Expert Lawyer Support Necessary?
Claims for original part damage difference and actual loss are complex processes that require meticulous adherence to both the technical provisions of insurance law and procedural rules. Failure to carry out the stages of application to the insurance company, mandatory mediation, and lawsuit/arbitration in the correct order, or signing a release form that waives rights, can lead to serious loss of rights. The examination of expert reports, which are the most critical evidence in litigation, to determine whether they accurately reflect original part costs, market prices without discounts, and actual loss, and to object when necessary, also requires expertise.
Especially in cases seen in regions such as Tuzla, Pendik, Kartal, Maltepe, Aydınlı, Orhanlı, Tepeören in Istanbul and Gebze, Darıca, Çayırova in Kocaeli, the support of a lawyer who is intimately familiar with the practices of local Civil Courts of Commerce and their pools of experts directly contributes to the course of the lawsuit. Based in Tuzla, 2M Hukuk Law Office, provides effective legal struggle and litigation services against unjust discounts and equivalent part impositions by insurance companies in disputes related to damage difference, diminished value, loss of use, and replacement vehicle compensation arising from traffic accidents.
