Commercial Property Insurance

Coinsurance Penalty
Estimator

Find out exactly what your insurer will pay on a partial claim — and how much the coinsurance penalty cuts that number when you're underinsured.

🛡️ Coinsurance Estimator

🛡️

Coinsurance Penalty Estimator

Commercial property — partial loss payout with underinsurance penalty

Property Values

Actual Replacement Value at Time of Loss ($) What it would cost to rebuild the structure from the ground up today, using current labor and material costs.

Policy Coinsurance Requirement (%) The minimum coverage-to-value ratio required by your policy to avoid a penalty. Check your declarations page.

Actual Insurance Limit Carried ($) The coverage limit shown on your current policy declarations — not the premium, the limit of insurance.

Amount of Partial Loss / Damage ($) The contractor's estimated repair cost for this specific loss event (fire, storm, water damage, etc.).

About Coinsurance

What is the coinsurance clause?

A coinsurance clause is a provision in most commercial property insurance policies requiring the policyholder to maintain coverage equal to a specified percentage (commonly 80% or 90%) of the building's full replacement cost. If you carry less than that minimum, the insurer treats you as a co-insurer on every partial loss claim — they only pay their proportional share. The clause does not apply to total loss claims up to the policy limit.

What is the "did/should" formula?

The coinsurance penalty is calculated using the ratio of what you did insure versus what you should have insured. The formula is: (Coverage Carried ÷ Required Minimum Coverage) × Loss Amount. If you carried $1.4M when you should have carried $1.6M, your ratio is 0.875 — meaning the insurer pays only 87.5% of any partial loss. The remaining 12.5% falls on you as the effective self-insured co-insurer.

Does the coinsurance penalty apply to total losses?

Not in the traditional sense. On a total loss, the insurer pays up to the policy limit. If your policy limit is $1.4M and the building burns to the ground, they pay $1.4M — you simply absorb the gap between that and the true $2M replacement cost. The coinsurance penalty formula specifically governs partial loss claims where the loss is less than the policy limit, which is by far the more common scenario.

How do I avoid a coinsurance penalty?

Get a current replacement cost appraisal. Building costs have risen substantially since 2020 — labor and material inflation means many properties insured three or four years ago are now significantly underinsured relative to their actual replacement cost. After any major renovation, addition, or significant market cost shift, update your policy limit. An Agreed Value endorsement eliminates the coinsurance clause entirely by having the insurer pre-agree that your limit is adequate — worth asking your broker about.

Commercial Property Insurance Guide

The Coinsurance Trap: Why Partial Claims Get Slashed and What You Can Do About It

You paid your premiums every year. You had a fire. Your contractor quoted $300,000 in repairs. So why is your insurance company only writing you a check for $262,500?

The answer is buried in a clause most business owners never read — and most insurance agents never explain in plain terms. It's called the coinsurance clause, and it operates as a built-in penalty system that kicks in whenever your coverage limit falls below a threshold tied to your property's actual replacement cost.

How the Clause Actually Works

Nearly every commercial property policy includes a coinsurance requirement — typically 80%, 90%, or 100%. The number tells you the minimum ratio of coverage to replacement value that you must maintain to collect a full claim payment on a partial loss.

If your building would cost $2,000,000 to rebuild today and your policy has an 80% coinsurance clause, you need to carry at least $1,600,000 in coverage. Carry less than that, and the insurer applies what's called the "did/should" formula to every partial loss:

Payout = (Coverage Carried ÷ Required Minimum) × Loss Amount Example: Replacement Value: $2,000,000 Coinsurance Req.: 80% → $1,600,000 required Coverage Carried: $1,400,000 Partial Loss: $300,000 Ratio = $1,400,000 ÷ $1,600,000 = 0.875 Payout = 0.875 × $300,000 = $262,500 Penalty = $300,000 - $262,500 = $37,500

That $37,500 comes out of your pocket — not the insurer's. You're effectively self-insuring the gap, whether you intended to or not.

Critical Point: The penalty applies on every partial loss claim, not just catastrophic ones. A $40,000 roof claim, a $75,000 water damage event, a $120,000 fire in one wing — each gets the same penalty ratio applied. These are the claims businesses file most frequently.

Why Buildings Are Underinsured More Than You'd Think

Most underinsurance isn't intentional. It happens quietly, over time, through a combination of factors that are easy to miss.

Construction Cost Inflation

Building material and labor costs have climbed dramatically since 2020. A property insured to 80% of replacement cost in 2019 may be carrying coverage equivalent to 55% or 60% of its actual replacement cost today — deep inside penalty territory — without any change to the policy itself.

Unreported Improvements

Adding a new HVAC system, expanding a warehouse, finishing a commercial kitchen, or updating electrical systems all increase replacement cost. Owners who don't notify their broker after improvements are often unknowingly underinsured within weeks of completing the work.

Original Coverage Based on Purchase Price

A property bought for $800,000 is not necessarily a property that costs $800,000 to rebuild. Market value and replacement cost are fundamentally different numbers. A building on expensive commercial land may carry a $1.2M market value with a $900,000 replacement cost — or vice versa. Insuring to market value rather than replacement cost is one of the most common underinsurance errors brokers encounter.

The Three Numbers That Matter

Number	What It Is	Where to Find It
Replacement Value	What it costs to rebuild today	Current appraisal or contractor estimate
Required Minimum	Coinsurance % × Replacement Value	Calculated — not on your policy
Carried Limit	Your policy's limit of insurance	Declarations page, "Limit of Insurance" line

If your carried limit is below the required minimum, the penalty ratio is already set. You simply don't know how expensive it is until you file a claim.

Practical Fixes Before Your Next Renewal

Order a replacement cost appraisal. A Marshall & Swift or similar commercial replacement cost estimator gives you a defensible number tied to current material and labor costs. Many insurers offer this at no cost through their underwriting departments.
Request an Agreed Value endorsement. This eliminates the coinsurance clause entirely. The insurer pre-agrees that your stated limit is adequate — no penalty applies, period. It typically requires a current appraisal and carries a modest premium increase, but it removes all ambiguity.
Review your limits after any renovation. Set a calendar reminder tied to your policy anniversary and any significant project completion. The replacement cost conversation should happen before the work is finished, not after the loss.
Separate insurable value from market value. Instruct your broker to quote based on replacement cost, not assessed value or purchase price. These numbers can differ by 30–50% on older commercial properties.

The Agreed Value Endorsement is the cleanest solution available. Ask your broker whether your current policy qualifies. Properties that carry one are not subject to the coinsurance formula under any partial loss scenario — you file the claim, they pay the claim up to the limit.

What the Insurer Won't Tell You

Insurers are not required to notify you that you're underinsured. The coinsurance clause is buried in the policy language — your declarations page shows a limit, a premium, and a coinsurance percentage, but not the calculation that determines whether you're in compliance with it.

That's why claims come as a shock. A business owner who consciously decided to carry $1.4M in coverage on a $2M building didn't necessarily realize they were accepting a 12.5% deductible on every partial loss. They were thinking about the premium, not the penalty math.

Run this calculator before your next renewal. If the required minimum exceeds your carried limit by even 5%, you have a coverage gap worth addressing — and the conversation with your broker costs nothing.

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