What Is Gap Insurance? Why Is Value Assessment Important in Casco Insurance?

Insurance and Inspection
Author: Mustafa Odabaşı
Creation: 21 October 2026

The small amount gained from the premium is largely recovered from the compensation at the time of damage in underinsurance.

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Underinsurance means the insured amount stated in your comprehensive (casco) policy falls below your vehicle's actual value on the date of damage; in this case, the insurance company reduces the compensation it pays in the same proportion as the ratio of the policy amount to the actual value. In other words, if your vehicle's actual value is TL 1,000,000 while the policy states TL 800,000, one fifth of the payment is deducted no matter how large your loss is. In short, underinsurance is the small saving visible in the premium turning into a major loss at the moment of damage.

Highlights

The payment formula is simple: insured amount divided by actual value, multiplied by the loss amount, minus the deductible.
Casco values Türkiye Sigorta Birliği list; queryable for vehicles up to 15 model years old.
Stating a value below the market value in the policy is the direct cause of the proportional deduction applied at the time of damage.
Diminished value is, as a rule, an item not covered by casco; it can be added to the policy as additional coverage.

What Is Underinsurance and How Does It Affect Damage Payments?

Eksik sigortanın bedelini çoğu sürücü hasar günü öğrenir: sigortacı, üstlendiği değer kadarını öder, kalanını değil.

Let me say this as someone who has been following this industry from the inside for over thirty years: underinsurance is a situation most drivers only notice at the moment of damage. It does not come to mind when the policy is renewed; it becomes clear when the payment is seen as insufficient in the appraisal report record. Yet the logic is clear from the start. The insurer has undertaken not the whole but a part of the value covered, and bears responsibility only in proportion to that part of the loss.

Let's go with a concrete example. Suppose the vehicle's actual market value is TL 1,000,000 and the insured amount in the policy is TL 800,000. Your vehicle sustains a loss of TL 100,000. The insurance company does not pay the entire loss; 800,000 / 1,000,000 = 80% it applies the ratio; in other words, it pays TL 80,000. The remaining TL 20,000 comes out of your pocket because you took out the policy at a low value. The greater the proportion of the vehicle affected by the damage, the heavier the deduction; in a situation close to a total loss, this difference becomes a cost that is hard to bear.

The reverse of the same logic also applies and is called overinsurance: stating the insured amount above the actual value. Here the premium is unnecessarily high, but the payment is still limited to the vehicle's actual value. In other words, the extra premium paid finds no counterpart at the time of damage; the balanced point is always the actual value.

How is the compensation calculated?

In underinsurance, the net compensation is found with the following formula: (Insured Amount / Actual Value) x Loss - Deductible. If there is a deductible in the policy, this amount is first subtracted from the payment, then the proportion is applied. In addition, the amount to be paid also depends on the degree of fault in the accident and the coverage of the policy; even a driver with major fault can receive payment within the coverage and limits of the casco policy, but the proportional deduction applies in every case.

How Is the Casco Value Determined?

Kasko value is a reference amount indicating the approximate value of a vehicle that can be used as a basis in insurance transactions; in everyday language it is also called the market value. The policy is priced based on this value and determines the upper limit of the compensation to be paid. In Türkiye, this value is mostly taken from the Turkish Insurance Association's kasko value list. The list covers vehicles up to 15 model years old; prices for new vehicles are based on the prices announced by authorized distributors including VAT and SCT. The 2026 list is already in current use in the calculation tools of major insurance companies.

The list has one limitation you should know: it does not include mileage, damage history, or cosmetic condition breakdowns. It gives a single average value for all second-hand vehicles of the same model year. For this reason, a low-mileage, well-maintained vehicle may have a real value slightly above the average in the list. To make a query, the vehicle's brand, production year, and model information are sufficient.

TSB list or market value?

The list gives a general framework; the market value, on the other hand, can take vehicle-specific criteria into account. In determining the value, the vehicle's age, mileage, equipment level, general condition, and the current sale prices of similar vehicles are evaluated. For damaged or totaled vehicles, basing the policy on the market value gives a more accurate result. Obtaining an independent expert inspection report during the policy renewal period is also a practical way to find the correct value. The fact that insurance companies have started to determine the kasko value according to current market values instead of carrying it over from the previous policy as they used to has made this task somewhat easier.

How Does the Vehicle's Annual Depreciation Affect the Policy?

The most common mistake here is this: the driver renews the remaining policy at the same amount as it was written three years ago. Yet the vehicle loses value every year, and after a while the amount in the policy either exceeds the real value or, as is more often the case, falls below it. Exceeding it means paying unnecessary premiums, while falling below means underinsurance. Neither outcome is desirable.

Another separate point that really needs attention is the concept of depreciation itself. The sale price of a vehicle repaired after an accident drops compared to its accident-free equivalent; this is called vehicle depreciation. Kasko, as a rule, does not cover this item, because it is not a primary expense arising from the repair. If depreciation coverage is separately included in the policy, the depreciation arising from the accident can be claimed from the insurance company; if the coverage is not in the policy, it can mostly be purchased as additional coverage. According to legal practice, even the at-fault vehicle owner can claim depreciation from their own kasko if this coverage is in their policy; the claim of the not-at-fault party is covered in proportion to the other party's fault. The primary payer in the accident is the at-fault party's compulsory financial liability insurance. The deadline to remember: a depreciation claim must be made within 2 years must be done. For the claim, a written petition is submitted to the insurance company, an expert is appointed; in files where no expert has been assigned, appointments are made sequentially through EKSİST.

How to Avoid Underinsurance?

Some vehicle owners deliberately understate their vehicle's value to lower their premiums. The policy indeed comes cheap; but this is like hanging an empty fire extinguisher on the wall. When damage occurs, the proportional deduction takes back many times the short-term savings. The path to follow to avoid falling into this trap is clear:

Before renewing the policy, query your vehicle's current comprehensive insurance value using the current model year list.
Consider your vehicle's mileage, equipment, and condition; if necessary, obtain an independent inspection report.
Compare the insured amount in the policy with this real value; if there is a difference, have the amount updated.
If the premium difference bothers you, consider options such as comprehensive insurance with a deductible; sharing the risk instead of lowering the value is a much more predictable path.
Check from the policy text how situations such as theft, heavy damage, or total loss will be covered; in these scenarios, the vehicle's current value is directly decisive.

In short the only way to be protected from underinsurance is to keep the amount in the policy consistent with the vehicle's real value. Comprehensive insurance taken out with an adequate amount is the prerequisite for receiving full payment at the time of damage.

Comprehensive or Traffic Insurance: Which Covers What?

The underinsurance debate grows even larger among drivers who confuse the boundary between the two insurance types. Traffic insurance is mandatory in Türkiye and pays for the other party's damage; not your own vehicle's damage. Comprehensive insurance, on the other hand, is optional and secures your own vehicle. The party that is faultless in an accident or has at least a 25% share of fault can claim compensation from the other party's insurance company. The fault ratio is determined by evaluating the accident report, witness statements, security camera footage, and compliance with traffic rules; the sum of primary and secondary fault ratios reaches 100%.

Feature	Traffic Insurance	Comprehensive Insurance
Obligation	Mandatory	Optional
What it pays for	The other party's damage	Your own vehicle's damage
Value determination	Based on coverage limits	Based on comprehensive insurance value / market value
Underinsurance risk	Not applied	If the amount is below the real value, a proportional deduction is made

If the other party has no insurance, a direct claim can be made against the at-fault driver or vehicle owner; the Guarantee Fund offers a path for bodily injuries, but vehicle damage is not within the fund's scope. This table also clearly shows that securing your own vehicle is only possible with comprehensive insurance - and the strength of that protection depends on the amount in the policy being realistic.

Frequently Asked Questions

Why was a deduction made from my compensation at the time of damage?

This is the most likely reason: if the insured amount in the policy was below the vehicle's real value on the date of damage, the payment is reduced by the ratio of the amount to the value. It is enough to compare your policy with the current comprehensive insurance value.

Does comprehensive insurance cover depreciation?

As a rule, it does not. However, if your policy includes depreciation as additional coverage, the depreciation resulting from the accident can be claimed from your insurance company; even the at-fault driver can make a claim if this coverage exists in their own policy.

Will a claim be paid if I have not paid the premium installment?

It may not be paid. There are court rulings stating that the claim amount is not paid due to the non-payment of the premium installment; you need to follow the policy not only in terms of value but also in terms of the payment arrangement.

Final Word: A Cheap Policy Can Be an Expensive Lesson

In the past, insurers would transfer the comprehensive insurance value exactly as it was from the previous policy; the fact that current market values are now used shows that the system works correctly, at least on the value side. The rest is the driver's responsibility: at every renewal period, compare the amount in the policy with the vehicle's actual value. A five-minute check prevents encountering deductions worth thousands of lira at the time of a claim. The most expensive savings I have seen in this profession were always the few dozen lira cut from the premium.