2.4 Coinsurance and Insurance to Value
Key Takeaways
- Coinsurance requires the insured to carry coverage equal to a stated percentage (commonly 80%) of property value; falling short makes the insured a co-insurer who shares every loss.
- Coinsurance formula: (Amount Carried ÷ Amount Required) × Loss = Claim, where Amount Required = Value × Coinsurance %.
- The penalty applies to PARTIAL losses, not just total losses, and the payment can never exceed the lesser of the actual loss or the policy limit.
- Agreed Value, inflation-guard endorsements, and annual value reviews are the practical defenses against a coinsurance penalty.
- Insurance-to-Value (ITV) = Amount of Insurance ÷ Property Value; reaching the coinsurance percentage (e.g., 80%) avoids the penalty.
Why Coinsurance Exists
Most property losses are partial, not total. If underinsurance carried no penalty, owners would insure a $500,000 building for only $100,000, pay a small premium, and still recover most partial losses — starving the insurer of premium for the real exposure. The coinsurance clause corrects this by penalizing underinsurance on every loss, encouraging owners to insure to value.
Common coinsurance percentages: 80% (most common), 90%, and 100%.
The Coinsurance Formula
Claim Payment = (Amount Carried / Amount Required) x Loss
| Term | Meaning |
|---|---|
| Amount Carried | The policy limit actually purchased |
| Amount Required | Property Value × Coinsurance % |
| Loss | The actual damage amount |
Two caps always apply: the payment can never exceed the actual loss or the policy limit, whichever is less. The deductible is then subtracted from the result.
Example 1 — Requirement Met
- Building value: $500,000; coinsurance 80%; policy limit $400,000; loss $100,000.
- Amount Required = $500,000 × 80% = $400,000.
- Ratio = $400,000 ÷ $400,000 = 100%.
- Claim = 100% × $100,000 = $100,000 — the full loss is paid.
Example 2 — Coinsurance Penalty
- Same building, but the owner carries only $300,000.
- Amount Required = $400,000; Amount Carried = $300,000.
- Ratio = $300,000 ÷ $400,000 = 75%.
- Claim = 75% × $100,000 = $75,000.
The insured eats a $25,000 penalty on a $100,000 loss because they were a co-insurer for 25% of the exposure.
Example 3 — Loss Exceeds the Limit
- Building value $1,000,000; coinsurance 80%; policy limit $700,000; loss $900,000.
- Amount Required = $1,000,000 × 80% = $800,000.
- Ratio = $700,000 ÷ $800,000 = 87.5%.
- Formula result = 87.5% × $900,000 = $787,500.
- But the payment cannot exceed the $700,000 policy limit, so the insurer pays $700,000.
This is the most common exam trap: students apply the formula and forget the policy-limit cap.
Avoiding the Coinsurance Penalty
| Method | How it helps | Caveat |
|---|---|---|
| Carry adequate limits | Insure to at least the required % of value | Values drift; review annually |
| Agreed Value clause | Suspends coinsurance entirely | Needs appraisal / statement of values |
| Inflation guard endorsement | Auto-increases limits 4-8%/yr | Does not guarantee compliance |
Insurance to Value (ITV)
ITV Ratio = Amount of Insurance / Property Value
| ITV ratio | Status | Consequence |
|---|---|---|
| 100%+ | Fully insured | Full loss recovery |
| 80-99% | Meets typical 80% coinsurance | No penalty |
| Below 80% | Underinsured | Coinsurance penalty applies |
Worked ITV: $400,000 of coverage on a $500,000 building gives ITV = $400,000 ÷ $500,000 = 80%, exactly meeting an 80% requirement.
Key Exam Points
- Coinsurance bites on partial losses, not only total losses.
- Payment is the lesser of the formula result, the actual loss, or the policy limit.
- 80% is the most common requirement; the deductible comes off after the coinsurance math.
- Agreed Value is the clean way to eliminate the penalty.
- The shortfall is borne by the insured, who becomes a co-insurer.
Quick check: A $640,000 requirement met with $500,000 of coverage pays only $500,000/$640,000 = 78.125% of any loss — short of the 80% target and penalized.
Step-by-Step Method for Any Coinsurance Question
Work every coinsurance problem in the same four steps and you will not miss the cap or the deductible:
- Compute Amount Required = property value × coinsurance percentage.
- Form the ratio = amount carried ÷ amount required. If the ratio is 100% or more, treat it as 100% (you never collect a bonus for over-insuring).
- Apply the ratio to the loss to get the formula result.
- Cap and net — take the lesser of the formula result, the actual loss, and the policy limit, then subtract the deductible.
Fully worked: value $500,000; coinsurance 80% (required $400,000); carried $360,000; loss $50,000; deductible $1,000. Ratio = $360,000 ÷ $400,000 = 90%. Formula = 90% × $50,000 = $45,000. It is below both the loss and the limit, so subtract the deductible: $45,000 − $1,000 = $44,000 paid. The $5,000 gap is the coinsurance penalty plus the deductible.
Coinsurance on Business Income
Coinsurance is not limited to buildings. Business income coverage uses a coinsurance percentage (commonly 50%, 60%, 70%, 80%, or higher) applied to the 12-month net income plus continuing expenses the business would have earned had no loss occurred. If an insured selects a 50% business-income coinsurance percentage, they must carry a limit equal to at least half of projected annual net income plus continuing operating expenses; otherwise the same proportional penalty applies to a business-interruption claim.
The business income report/worksheet is how the insured supports the figure, and an agreed value option (or the monthly limit of indemnity and maximum period of indemnity options) can be used to sidestep the coinsurance test on time-element coverage.
Why Insurers Use 80% Rather Than 100%
A common exam reasoning question asks why the standard requirement is 80% rather than 100%. The answer: most losses are partial, so requiring 80% gives the insurer adequate premium relative to true exposure while building in a margin for ordinary fluctuations in property value — owners are not penalized for a small valuation drift, but gross underinsurance is discouraged. Setting the bar at 100% would penalize honest insureds for minor inflation between renewals; 80% balances fair pricing against ease of compliance, which is exactly the policy rationale the exam wants you to recognize.
A building is worth $800,000 with an 80% coinsurance requirement. The owner carries $500,000 in coverage and suffers a $200,000 fire loss. What is the claim payment?
Which of the following eliminates the coinsurance penalty?
An insured has $200,000 coverage on a building worth $400,000 with 80% coinsurance. A total loss occurs. What does the insurer pay?