The Coinsurance Clause & Penalty Math
Key Takeaways
- Coinsurance requires the insured to carry a stated percentage (often 80%) of value or face a proportionate penalty on partial losses.
- Payment = (carried / required) x loss − deductible, capped at the limit; required = value x coinsurance percentage.
- If the carried-to-required ratio is 1.0 or more, there is no penalty and the loss is paid in full up to the limit.
- Coinsurance applies only to partial losses and is tested at the time of loss; agreed-value or inflation-guard provisions can suspend it.
Why Coinsurance Exists
Most property losses are partial, not total, so an insured tempted to under-insure could buy a small limit, pay a small premium, and still expect most partial claims paid in full. The coinsurance clause counters this by requiring the insured to carry insurance equal to a stated percentage of the property's value, usually 80, 90, or 100 percent. If the insured carries less, the insurer pays only a proportionate share of a partial loss and the insured becomes a co-insurer for the rest.
The Coinsurance Formula
The exam will give you four numbers, the limit carried, the coinsurance percentage, the property value, and the loss, and expect the formula:
Payment = (Insurance carried / Insurance required) x Loss − Deductible, capped at the policy limit.
Insurance required equals the property value multiplied by the coinsurance percentage. If the ratio is 1.0 or greater, there is no penalty and the loss is paid in full up to the limit.
| Step | Action |
|---|---|
| 1 | Insurance required = value x coinsurance % |
| 2 | Ratio = carried / required (cap at 1.0) |
| 3 | Payment = ratio x loss |
| 4 | Subtract the deductible |
| 5 | Cap at the policy limit |
Worked Penalty Example
A building is worth $500,000 and the policy has an 80 percent coinsurance clause, so the insured must carry at least $400,000. Suppose the insured carries only $300,000 and suffers a $100,000 loss with a $1,000 deductible.
- Insurance required = $500,000 x 0.80 = $400,000
- Ratio = $300,000 / $400,000 = 0.75
- Payment = 0.75 x $100,000 = $75,000
- Less deductible = $75,000 − $1,000 = $74,000
The insured absorbs the $25,000 coinsurance penalty plus the deductible because of under-insurance. Had the insured carried the required $400,000 or more, the ratio would be 1.0 and the policy would pay the full $100,000 loss (less the deductible), up to the limit.
Important Limits on the Penalty
Coinsurance applies only to partial losses. In a total loss, the penalty disappears because the most the policy ever pays is the limit, and a total loss to a property worth more than the limit simply pays the limit. Coinsurance is also tested at the time of loss, so values that rise during the policy term (inflation) can create a hidden penalty unless the insured raised the limit or carries an agreed-value or inflation-guard endorsement that suspends or offsets coinsurance.
Related Provisions
An agreed-value option waives coinsurance entirely when the insured files a statement of values and carries the agreed amount. A blanket limit covering several buildings or locations can soften coinsurance because the single limit is measured against the combined value. The exam frequently pairs a coinsurance computation with one of these provisions and asks how the settlement changes, so practice the formula until setup is automatic and watch for the words 'agreed value' or 'inflation guard' that switch the penalty off.
A building worth $1,000,000 has an 80% coinsurance clause. The insured carries $600,000 and suffers a $200,000 loss with no deductible. What does the policy pay?
Coinsurance penalties apply to which kind of loss, and what suspends the requirement?
Mastering the Coinsurance Calculation
Coinsurance problems are pure setup. Write the formula first, payment equals carried divided by required, times the loss, minus the deductible, and the arithmetic falls into place. Required insurance is the property value times the coinsurance percentage; if carried equals or exceeds required, the ratio is capped at 1.0 and there is no penalty. The most common error is dividing by the property value instead of by the required amount, which inflates the penalty.
A worked variation: a $250,000 building with 90 percent coinsurance requires $225,000. If the insured carries $180,000 and suffers a $60,000 loss with a $500 deductible, the ratio is $180,000 divided by $225,000, or 0.80, so the policy pays 0.80 times $60,000 less $500, which is $48,000 minus $500, or $47,500. The insured absorbs the $12,000 penalty plus the deductible.
| Variable | How to find it |
|---|---|
| Required | Value × coinsurance % |
| Ratio | Carried ÷ required (max 1.0) |
| Gross payment | Ratio × loss |
| Net payment | Gross − deductible (≤ limit) |
Two facts limit the penalty and are tested directly. First, coinsurance applies only to partial losses; in a total loss the policy simply pays the limit, so no penalty applies. Second, coinsurance is measured at the time of loss, so rising property values during the term can create a hidden penalty unless the insured raised the limit or carries an agreed-value or inflation-guard provision that suspends or offsets the requirement.
When a question mentions agreed value or inflation guard, recognize that the penalty is switched off, and when it gives a total loss, recognize that the limit, not the formula, governs.
The most common coinsurance error is dividing by the property value instead of by the required amount (value times the coinsurance percentage). Always compute required first, then the carried-to-required ratio (capped at 1.0), then multiply by the loss and subtract the deductible. Two facts limit the penalty: coinsurance never reduces a total loss (the limit is simply paid), and an agreed-value or properly maintained inflation-guard provision switches the penalty off.
When a problem mentions either provision, the penalty does not apply, and when it describes a total loss, the limit governs.