What business income coverage actually insures
Business income coverage pays the earnings you would have made and the operating expenses you keep paying while the doors are shut. Under the ISO CP 00 30 form, the insured quantity is net income plus continuing operating expenses. That definition is the whole subject: everything hard about sizing this coverage comes from deciding which expenses continue.
The easier way to reach the same number is from the top of the income statement. Take revenue and subtract only the expenses that genuinely stop — the goods you would not buy, the freight you would not pay, the commissions you would not owe. What is left is business income, because it is exactly net income plus everything that keeps running. Rent keeps running. Debt service keeps running. Insurance, property taxes, management salaries and, in most cases, the key employees you cannot afford to lose all keep running.
This is where most worksheets go wrong. Classifying all payroll as non-continuing is the classic error, and it can cut the calculated business income value by a third or more. If you would keep a machinist on the books through a nine-month rebuild rather than lose them to a competitor, that payroll continues and belongs inside the covered figure.
Property damage and business income are two halves of one loss. Size the building and contents side with the commercial property blanket limit calculator, and understand the coinsurance mechanics in isolation with the insurance-to-value calculator.
Why the period of restoration, not the calendar year, sets the limit
A common shortcut is to buy twelve months of business income and stop thinking. That is right only by coincidence. The policy pays from the date of loss until the property should be repaired or replaced with reasonable speed — the period of restoration — and that period has nothing to do with your policy year. A single-tenant warehouse with commodity racking might be back in ninety days. A food plant with a custom production line, a state licence and a USDA inspection to re-earn might be eighteen months out, and the equipment lead time alone can be most of it.
So the limit is projected business income scaled by m ÷ 12. Above twelve months you need an extended period of indemnity endorsement, because the base form's period of restoration ends when the property is restored, not when your customers come back. Below twelve months you can buy less, but the coinsurance clause will punish you for it, and that is the second half of the arithmetic.
The coinsurance requirement is tested against twelve months of business income no matter what your restoration period is. Carry 80% coinsurance and you must carry a limit of at least 80% of a full year's business income, or every claim — including a small one — is reduced by the ratio of what you carried to what you should have carried. Nothing about that reduction is capped at the size of the shortfall; a limit at half the requirement halves the payment on a $50,000 loss just as surely as on a $5,000,000 one.
Extra expense is added on top. It is the money you spend to shorten the shutdown — renting temporary premises, expediting a replacement machine, paying overtime to rebuild inventory — and it is worth buying because a dollar of extra expense often saves several dollars of lost income.
Worked example: a $5,000,000 distributor with a 12-month restoration
A distributor budgets $5,000,000 of revenue for the coming year. Purchases of merchandise and inbound freight, which stop entirely if the warehouse burns, come to $2,000,000. Sales commissions and utilities that also stop come to $300,000. Payroll, rent, insurance and the owner's salary all continue. Coinsurance on the declarations page is 80%, the waiting period is 72 hours, and the current limit is $3,000,000.
- Business income value. $5,000,000 − $2,000,000 − $300,000 = $2,700,000.
- Project it forward. With no growth assumed, projected business income stays at $2,700,000. At 10% growth it would be $2,970,000.
- Scale to the period of restoration. Twelve months, so $2,700,000 × 12 ÷ 12 = $2,700,000 of business income exposure.
- Test coinsurance. Requirement = $2,700,000 × 80% = $2,160,000. The $3,000,000 carried is $3,000,000 ÷ $2,160,000 = 138.9% of the requirement, so no penalty applies.
- Price the waiting period. $2,700,000 ÷ 365 = $7,397 a day. Seventy-two hours is three days, so $22,192 falls inside the time deductible and is yours.
Now change one input. Stretch the restoration period to eighteen months and grow revenue 10%: the exposure becomes $2,970,000 × 1.5 = $4,455,000, plus a $100,000 extra expense allowance, so $4,555,000. Against that, a $2,000,000 limit is only $2,000,000 ÷ $2,376,000 = 84.2% of the coinsurance requirement, so a claim would settle at 84.2 cents on the dollar and exhaust at $2,000,000 less than halfway through the shutdown. Both failures come from the same missing conversation about how long recovery really takes.
How to read the result
The limit-carried percentage is the number to look at first. At or above 100% of the requirement, claims settle without a coinsurance reduction. Below it, every claim is multiplied by that percentage, which is why the figure is shown to one decimal place rather than rounded — 99.4% is a penalty, and it is a penalty on a total loss as well as on a small one.
The recommended limit and the coinsurance requirement answer different questions and will usually differ. The requirement is the minimum the policy language demands. The recommended limit is what you would actually need to survive a shutdown of the length you estimated. Where the restoration period is under twelve months the requirement is the binding constraint; where it is over twelve months the recommended limit is. Buy the larger of the two.
Treat the waiting-period figure as information, not as a problem to solve. Shorter waiting periods cost premium, and a 72-hour period on a business of this size costs about three days of gross earnings. That is normally a cheap retention. It matters far more for a business with high daily earnings and a genuine risk of short interruptions — a data centre, say — where a 24-hour period may be worth the extra premium.
Finally, sanity-check the growth assumption against the limit you already carry. Business income limits are frequently set once and left, so a business growing 10% a year drifts out of coinsurance compliance in about two years without anything visible changing.
How the coinsurance penalty scales with the shortfall
| Limit as % of requirement | Recovery factor | Paid on a $500,000 loss | Reduction |
|---|---|---|---|
| 100% or more | 1.000 | $500,000 | $0 |
| 95% | 0.950 | $475,000 | $25,000 |
| 90% | 0.900 | $450,000 | $50,000 |
| 80% | 0.800 | $400,000 | $100,000 |
| 70% | 0.700 | $350,000 | $150,000 |
| 50% | 0.500 | $250,000 | $250,000 |
Each row is loss × min(1, limit ÷ requirement), the same expression the calculator uses. The reduction applies to losses of every size, not only to large ones.
The form this calculator follows
The arithmetic here follows the ISO CP 00 30 Business Income (and Extra Expense) Coverage Form and the CP 15 15 Business Income Report/Worksheet that underwriters use to set the limit. Two options on that form change the answer materially. Maximum Period of Indemnity caps recovery at 120 days and deletes coinsurance entirely. Monthly Limit of Indemnity replaces coinsurance with a fraction — one third, one quarter or one sixth — of the limit available in any one month. Both are common on smaller accounts and neither is modelled here; if either appears on your declarations page, the coinsurance output does not apply to your policy.
Mistakes that make a business income limit wrong
- Treating all payroll as non-continuing. If you would keep skilled staff through the rebuild, that payroll continues and belongs in the covered figure. This single misclassification underinsures more accounts than anything else on the worksheet.
- Using last year's revenue. The worksheet is a forward projection for the coming policy year. A growing business that reports historical figures is underinsured on the day the policy incepts.
- Estimating the period of restoration from the builder's quote. Demolition, debris removal, permitting, equipment lead times, re-inspection and rehiring all sit outside the construction schedule. Ask what the longest single lead time is on the plant floor.
- Forgetting that customers do not return on day one. The base form stops paying when the property is restored. An extended period of indemnity endorsement continues coverage while sales recover, and it is inexpensive relative to what it protects.
- Ignoring dependent property exposure. If a single supplier or a single major customer going down would stop your revenue, that is contingent business income coverage and it is not included in the limit calculated here.
- Assuming the deductible is money. Business income deductibles are usually time. Seventy-two hours of a business earning $7,400 a day is a $22,000 retention that never shows up as a dollar figure on the declarations page.
Where this fits in a commercial insurance programme
Business income sits between property and liability, and it is consistently the coverage where insureds are most surprised by their own limits. Property values can be appraised; liability limits are bought against a market norm; business income requires an honest internal estimate of how long a recovery would take, which is a question nobody in the business has an incentive to answer pessimistically.
Two adjacent covers do work this one will not. Contingent business income responds when a supplier or customer, not you, suffers the physical damage. Cyber business interruption responds when the cause is a network event rather than physical damage — a distinction that matters because the standard property form requires direct physical loss, which a ransomware event generally is not. Size that exposure separately with the cyber liability coverage limit calculator.
Revisit the worksheet annually alongside your other rated exposures. Payroll drives workers compensation premium through the workers comp premium calculator and loss history drives it further through the experience modifier calculator; the same payroll figure that moves those numbers is the one that decides how much of your operating cost continues during a shutdown. Getting it right once serves several purposes.