To calculate a business interruption loss, project the revenue you would have earned during the shutdown, subtract the expenses you didn’t have to pay because you weren’t operating, and add any extra costs you incurred to speed up the recovery or keep serving customers. Expressed from the bottom up, the same number equals the net profit you would have earned, plus the fixed expenses that kept arriving while you were closed, plus those extra costs. Every figure in that equation depends on your historical financials, the length of time your property reasonably takes to repair, and the specific coverage mechanics inside your policy.
The Core Formula
Two paths lead to the same number, and knowing both keeps you from double-counting or leaving money out.
The top-down version: projected revenue during the shutdown, minus non-continuing expenses, plus extra expenses. The bottom-up version: projected net income, plus continuing fixed expenses, plus extra expenses. Retail and service businesses that track daily sales often find the top-down approach easier. Manufacturers and businesses with complex cost structures tend to work more cleanly from the bottom up.
The key phrase in both versions is “would have.” You are not measuring what actually happened during the shutdown. You are projecting what should have happened based on your track record, then comparing that projection against the reduced reality. The gap is your loss.
The Period of Restoration
Every dollar in the calculation is tied to a specific window of time called the period of restoration. Under standard ISO policy language, this period begins on the date of the physical damage and ends on the date the property should be repaired, rebuilt, or replaced with reasonable speed and similar quality.1Property Insurance Coverage Law. ISO Form CP 00 30 – Business Income Coverage Form The word “should” is doing heavy work. The policy does not measure how long repairs actually took if you dragged your feet. It measures how long they reasonably should have taken.
The end date is where most disputes land. Your insurer will argue the building could have been repaired faster. You will argue the timeline was reasonable given permit delays, material shortages, or contractor availability. Document everything: permit applications, inspection results, backorder notices. Delays caused by code upgrades required under local ordinances are typically excluded from the standard form unless you purchased a separate law-and-ordinance endorsement.
The Extended Period After Reopening
The standard business income form includes a built-in extension that covers lost income for up to 60 days after repairs are finished or should have been finished.2International Risk Management Institute. Extended Period of Indemnity Endorsement or Option Reopening the doors does not instantly restore your customer base. A restaurant closed for four months loses regulars to other places, and winning them back takes time. If 60 days is not enough for your business, an optional endorsement can push the window further.
Projecting Lost Net Income
Net income projection starts with historical revenue, adjusted for trends. If your sales were growing 8% year over year before the loss, the projection should reflect that growth during the restoration period. Seasonal variation matters too. A beachside hotel that suffers hurricane damage in September has a very different loss profile than one hit in February. The projection should mirror what that specific stretch of months looked like historically, not just an annual average divided by twelve.
Continuing Expenses vs. Non-Continuing Expenses
Continuing expenses are the bills that kept arriving while you were shut down: rent or mortgage payments, property taxes, loan interest, insurance premiums, alarm monitoring, management salaries. These costs do not pause because your revenue stopped, and the policy reimburses them because without coverage you would burn through reserves just keeping the lights on at a business that cannot earn.
Non-continuing expenses get subtracted out. Raw materials you did not purchase, hourly wages you did not pay, variable utility costs that dropped to near zero. Reimbursing you for costs you never incurred would be a windfall, and insurance is designed to make you whole rather than put you ahead.
The Ordinary Payroll Trap
Many policies contain an endorsement that limits or excludes coverage for “ordinary payroll,” meaning wages for rank-and-file employees who are not officers, executives, department managers, or workers under contract.3Property Insurance Coverage Law. ISO Form CP 15 10 – Ordinary Payroll Limitation or Exclusion If your policy includes this endorsement, it may cover ordinary payroll for only a set number of days, or it may exclude it entirely.
For a business that depends on skilled hourly workers who are hard to rehire, this limitation can be devastating. Check your declarations page before a loss happens. If ordinary payroll is limited to 60 or 90 days and your realistic restoration timeline is longer, talk to your agent about removing the limitation.
Extra Expenses
On top of lost income and continuing costs, most business income policies cover extra expenses you incur to reduce the duration or severity of the interruption. Common examples include renting temporary space, leasing replacement equipment, paying overtime to contractors for faster rebuilding, and notifying customers about a temporary location. The standard business income and extra expense form, ISO CP 00 30, bundles this coverage alongside the income loss provisions.4International Risk Management Institute. Whats New in the 2000 Edition ISO Commercial Property Forms CP 00 30
The critical qualifier is that extra expenses are reimbursable only if they reduce the overall business income loss. Renting a pop-up shop that generates $20,000 in revenue during a month when it costs you $5,000 clearly passes the test. Renting a luxury temporary office that costs more than the income it preserves does not. Keep separate ledgers for extra expenses so they do not blur into your regular continuing costs, and save every invoice.
Some policies also include a sub-limit for claim preparation costs, covering fees for forensic accountants or loss consultants you hire to build your claim. Check that language before assuming you have to pay those fees out of pocket.
Gathering the Records to Build the Projection
Before you can run the formula, you need the raw data. Start with profit and loss statements and federal tax returns for the past two to three years. These establish your revenue baseline and seasonal patterns. Payroll records, purchase journals, and daily sales data from your accounting software fill in the granular detail that tax returns alone cannot provide.
Most commercial property policies require you to complete a Business Income Report/Worksheet, designated as ISO Form CP 15 15, either at policy inception or as part of your claim. The worksheet walks you through gross sales, cost of goods sold, operating expenses, and projected net income to arrive at your total business income exposure for a twelve-month period.5BSR Insurance. Business Income Report/Work Sheet – ISO Form CP 15 15 Completing it accurately matters beyond the claim itself: the worksheet also feeds into your coinsurance calculation.
Non-financial records also help. Construction permits, contractor estimates, correspondence with your landlord, and photographs of the damage all establish the timeline and scope of your loss. Keep separate files for pre-loss financials, post-loss expenses, and rebuilding costs.
Policy Mechanics That Change the Number
Waiting Periods
Most business interruption policies impose a time-based deductible, commonly called a waiting period. Depending on your policy, the first 24, 48, or 72 hours after the damage occurs are not covered. Some policies make this a true deductible, meaning you absorb the loss for that initial period permanently. Others apply it retroactively once the waiting period expires, covering you back to the moment of the loss. Read your policy language carefully, because the difference can represent thousands of dollars.
Policy Limits
Your recovery can never exceed your policy’s limit of insurance, regardless of how large the calculated loss is. If your business income limit is $500,000 and your actual loss comes to $750,000, you collect $500,000. Underinsurance is rampant in business income coverage because most owners underestimate how long a restoration will take. A limit that assumes a three-month shutdown is dangerously thin if rebuilding actually takes nine months.6Chubb. My Business Income Consultation FAQs
Coinsurance Penalties
Coinsurance is the penalty clause that catches underinsured businesses off guard. If your policy has an 80% coinsurance requirement, you must carry a limit equal to at least 80% of your annual net income plus operating expenses. Fall short, and the insurer reduces your payout proportionally using this formula: the amount of insurance you carried, divided by the amount you should have carried, multiplied by your loss.
A concrete example makes the sting clear. Say your annual business income value is $2,870,000 and your policy requires 100% coinsurance. You should be carrying $2,870,000 in coverage, but you only purchased $1,800,000. Your ratio is roughly 63%. If you file a $500,000 claim, the insurer pays only about $315,000. You absorb the other $185,000. Coinsurance penalties do not apply to the extra expense portion of your coverage, only to business income loss.6Chubb. My Business Income Consultation FAQs This is why completing the CP 15 15 worksheet accurately at policy inception matters so much.
When the Shutdown Isn’t Caused by Damage to Your Property
The calculation above assumes damage to your own premises. Two coverage extensions use the same formula but have different triggers, and both have narrow requirements worth knowing before you start building a claim.
Civil authority coverage applies when a government order prohibits access to your premises due to physical damage within one mile of your location, caused by a peril your policy covers. The coverage period runs up to four weeks from the date of the order. Some policies extend the distance through endorsement. The order must actually prohibit access, not just discourage it, and the damage must be to property other than yours.
Contingent business interruption coverage protects you when physical damage at a supplier or key customer’s property disrupts your operations.7Casualty Actuarial Society. Contingent Business Interruption A supplier that cannot ship because of a power outage or evacuation order, without actual damage to its property, typically does not trigger CBI coverage. Policy wording also matters for depth: if the policy specifies “direct suppliers,” a problem at your supplier’s supplier may not be covered.
Your Duty to Mitigate
Insurance does not entitle you to sit idle during a shutdown. Policies require you to take reasonable steps to reduce your income loss, whether that means operating from a temporary location, filling orders through a competitor, or using existing inventory to keep serving customers. A business that could have partially reopened within weeks but waited three months for a perfect restoration will find its claim reduced accordingly.
The standard is reasonableness, not perfection. Nobody expects you to spend $100,000 on mitigation to save $50,000 in lost income. But if a viable temporary arrangement was available at modest cost, your insurer will argue you should have pursued it. Mitigation costs are usually covered as extra expenses, so spending money to reduce your downtime often costs you nothing out of pocket while preserving your claim.
Taxes on What You Collect
Business interruption proceeds that replace lost profits are taxable as ordinary income. If the income would have been taxable when you earned it through normal operations, the insurance payment that replaces it is equally taxable. The IRS defines gross income broadly as income from whatever source derived, and there is no specific exclusion for business interruption proceeds.8Office of the Law Revision Counsel. 26 USC 61 – Gross Income Defined
Proceeds that reimburse actual expenses you paid, like extra expense reimbursements, are generally tax-neutral because they offset a deductible cost. You spent the money (deduction) and got reimbursed (income), so they wash. The lost-profit component hits your return as ordinary business income. Factor this into your recovery planning. A $200,000 payout for lost profits is really more like $140,000 to $160,000 after federal and state taxes, depending on your bracket and entity structure.
Submitting the Number and Disputing It
Finalizing your claim means assembling the full calculation package and submitting it alongside a signed, sworn proof of loss. Most policies require the proof of loss to be given under oath, which typically means notarized. Courts have held that a proof of loss bearing a reused or transplanted notarization is invalid, so if you revise any figures, the entire document must be re-signed and re-notarized. Policy deadlines for submitting a proof of loss are enforceable, and missing them can jeopardize your entire claim.
Disputes over the dollar amount are common, and most commercial property policies include an appraisal clause designed to resolve them without litigation. Either you or the insurer can make a written demand for appraisal. Each side selects an independent appraiser, and the two appraisers choose an umpire. If the appraisers cannot agree on an umpire, either party can ask a court to appoint one.9Insurance Appraisal and Umpire Association. What Is Appraisal A decision agreed to by any two of the three is binding on the amount of loss. Each side pays its own appraiser, and both split the umpire’s costs equally.
Appraisal resolves only how much the loss is worth. It does not address whether the loss is covered in the first place. If the dispute is about coverage rather than valuation, appraisal will not help, and legal counsel becomes the next step.