Here's a scenario that surprises property owners every year: a business has a small fire — $50,000 in damage, well under its policy limit — and the insurer pays only $30,000 of it. Nothing was excluded. The claim was covered. The owner just got hit with a coinsurance penalty for being underinsured. It's one of the most common and least understood ways a covered loss turns into a partially paid one.
What is a coinsurance clause?
It's a condition in most commercial property policies that requires you to insure your building and contents to a set percentage of their full value — usually 80%, 90%, or 100%. The logic is a trade: insurers charge a lower rate when you insure close to full value, because they collect premium proportional to the real risk. In return, you promise to carry a limit at or above that percentage.
The catch is in the penalty for breaking that promise.
How the coinsurance penalty works
If a loss happens and you were insured below the required percentage, the insurer doesn't just quietly pay your limit — it reduces the payment on every loss by the same proportion you were underinsured. The formula is:
(Amount of insurance you carried ÷ Amount you should have carried) × the loss − deductible
An example makes it concrete. Say your building is worth $1,250,000 and your policy has an 80% coinsurance clause — so you're required to carry at least $1,000,000. You only carried $500,000. That's half the requirement. Now a $200,000 fire happens:
- $500,000 carried ÷ $1,000,000 required = 0.5
- 0.5 × $200,000 = $100,000 (minus your deductible)
Even though your $500,000 limit was more than enough to pay a $200,000 loss, you collect only about $100,000 — because you satisfied only half the coinsurance requirement. The penalty applies to partial losses too, which is exactly why it blindsides people: you don't have to have a total loss to feel it.
Why owners end up underinsured
The value the penalty is measured against is usually replacement cost — and it drifts upward over time while policy limits often don't:
- Construction costs rise year over year, so a building insured to value five years ago may be well under today.
- Improvements and additions increase value but don't automatically increase the limit.
- Lowball limits to save premium — intentionally insuring to less than value to cut the bill — set up the exact penalty that bites at claim time.
This is the practical side of insurance-to-value: the limit on your policy has to track what it would actually cost to rebuild, not what you paid or what it's worth on the market. (It's closely tied to the actual cash value vs. replacement cost question — how the loss is valued in the first place.)
How to avoid a coinsurance penalty
1. Insure to the correct replacement value and review it regularly, especially after improvements or in a high-inflation construction market. See commercial property insurance basics and how much does commercial property insurance cost. 2. Ask about an agreed value option. This suspends the coinsurance clause for the policy term when you and the insurer agree on the property's value up front — removing the penalty risk entirely for that period. 3. Add inflation guard, which automatically increases your limit over the policy term to keep pace with rising costs. 4. Don't underinsure to save premium. The savings are small; the penalty on a real loss can be enormous — and it also affects your business interruption recovery if income limits are understated.
Our approach
At Cory Washington & Co., we take insurance-to-value seriously because the coinsurance penalty is one of the few ways a *covered* loss still leaves you paying out of pocket. We help you set property limits to real replacement cost, use agreed value or inflation-guard where it makes sense to take the penalty risk off the table, and revisit your values as costs and your property change — so a claim is paid in full, not pro-rated. See our commercial property insurance overview for more.
Not sure whether your property is insured to value? Request a quote or a policy review and we'll check your limits and coinsurance terms with you.
Frequently Asked
What is a coinsurance clause in commercial property insurance?
It's a condition that requires you to insure your property to at least a set percentage of its value — commonly 80%, 90%, or 100%. In exchange for insuring close to full value, you get a better rate. But if you're underinsured below that percentage when a loss happens, the insurer applies a coinsurance penalty and pays only a portion of the claim — even if the loss was far smaller than your limit.
How does the coinsurance penalty work?
The insurer divides the amount you did carry by the amount you should have carried (the required percentage of value), and pays the claim by that same ratio, minus your deductible. For example, if you should have carried $1,000,000 (at 80% coinsurance on a $1,250,000 building) but only carried $500,000, you satisfied half the requirement — so the insurer pays only about half of a covered loss, and you absorb the rest. The penalty applies to every loss, not just a total loss.
How do I avoid a coinsurance penalty?
Insure your property to its correct replacement value and keep that value updated as construction costs rise and as you add or improve property. Two tools help: an agreed value option, which suspends the coinsurance clause when you and the insurer agree on the value up front, and inflation-guard, which automatically increases your limit over time. The core fix is accurate insurance-to-value — reviewing your limits regularly so you're never caught underinsured.
This article is general information for business owners, not insurance or legal advice, and does not bind or alter coverage. Policy terms, eligibility, and pricing vary by carrier and state — confirm specifics with our licensed team before making decisions.