Coinsurance indicates how an insurer and an insured will share the costs of a bill that exceeds the insurance policy's deductible up to the policy's stop loss. It is expressed as a percentage or pair of percentages generally with the insurer's portion stated first. The maximum percentage the insured will be responsible for is generally no more than 50%. Once the insured's out-of-pocket expenses equal the stop loss the insurer will assume responsibility for 100% of any additional costs.
Coinsurance is a penalty imposed on the insured by the insurance carrier for under reporting/declaring/insuring the value of tangible property or business income. The penalty is based on a percentage stated within the policy and the amount under reported. As an example:
''A building actually valued at $1,000,000 has an 80% coinsurance clause but is insured for only $750,000. Since its insured value is less than 80% of its actual value, when it suffers a loss, the insurance payout will be subject to the underreporting penalty. For example: It suffers a $200,000 loss. The insured would recover $750,000 ÷ (.80 × 1,000,000) × 200,000 = $187,500 (less any deductible).
In this example the underreporting penalty would be $12,500.
The most commonly issued coinsurance percentage would be 80% but can be as high as 100%. The latter [100%] would impose the greatest penalty for under reporting. For this reason, it is vital that values of property are accurately reported and updated annually to reflect inflation and other increases in cost.
Owner's title insurance policy forms of the American Land Title Association created between 1987 and late 2006, contain coinsurance clauses. For partial losses, they require the insured carry a percentage of the risk of loss in two circumstances. The first is if the insured did not insure its title for at least 80 percent of its market value at the time the policy was issued. In this case, the insurer will pay only 80 percent of the loss. The second is when improvements constructed on the property after the policy is issued increase the property's value by at least 20 percent above the amount of the policy. In this case, the insurer will pay a percentage of the claim equal to the ratio of 120 percent of the amount of insurance purchased divided by the sum of the amount of insurance and the cost of the improvements.
Coinsurance is also used among U.S. domestic title insurers in a manner similar to that described below for the international insurance market.
Coinsurance is generally widely used in the European insurance market. In this context, a common insurance contract is used and the risk is shared based on percentages between the insurance companies. Often, one insurance company will lead. When leading the insurance company will be responsible for administering various aspects of the insurance policy, such as premium, any claims and the insurance documents. In this situation, a charge is levied (termed Lead Office commission).