Nov 4
A business interruption claim calculation under a typical UK gross profit policy works out the turnover you lost during the indemnity period, applies your rate of gross profit to that shortfall, adds the reasonable extra costs you incurred to keep trading, and deducts any costs you saved. The policy definitions decide almost every number in that sum, and they rarely match your statutory accounts. The insurer’s loss adjuster will build their own version from your records. If you build yours first, with evidence behind every adjustment, you negotiate from your figures instead of theirs.
That’s the core of it. The rest of this guide walks through each stage, the clauses that quietly move the numbers, and where independent forensic work tends to make the biggest difference.
Most UK policies calculate the claim as: shortfall in turnover during the indemnity period × rate of gross profit, plus increased cost of working, minus savings. Each term has a policy definition. The rate comes from your last financial year. Standard turnover comes from the same months a year earlier, adjusted for trends. The result is then capped by your sum insured and reduced if you were underinsured.
Policy wordings vary, but the standard UK gross profit form is remarkably consistent across insurers. Reduction in turnover is the rate of gross profit applied to the amount by which turnover during the indemnity period falls short of standard turnover. Increase in cost of working is a separate item with its own limit.
The formula looks simple. The arguments sit inside the definitions.
Before any calculation, you need to know what each term means in your own wording. These are the ones that matter most:
| Term | What it usually means | Why it causes disputes |
|---|---|---|
| Insured gross profit | Turnover less uninsured working expenses, adjusted for stock | It is not the gross profit in your accounts |
| Rate of gross profit | Insured gross profit as a percentage of turnover for the last financial year | Year-end adjustments and one-off items can distort it |
| Standard turnover | Turnover in the matching months of the previous 12 months | Growth, seasonality and lost contracts all need adjusting |
| Indemnity period | From the incident until results stop being affected, capped by the maximum indemnity period | Many owners assume it ends when repairs finish |
| Increased cost of working | Extra spend necessarily and reasonably incurred to reduce the turnover loss | Capped by the gross profit it saves |
| Savings | Insured costs that stop or reduce because of the interruption | Often overlooked by claimants, rarely by adjusters |
| Sum insured and average | The policy limit, with a proportionate cut if you were underinsured | Can reduce a valid claim significantly |
Insured gross profit is usually turnover minus only the costs your policy treats as uninsured, typically purchases of materials and other genuinely variable costs. Wages, rent and overheads normally stay inside insured gross profit. That is why it is often much higher than the gross profit shown in your accounts, and why so many businesses are underinsured.
This is the single most misunderstood part of business interruption cover. Your accountant’s profit and loss account might show a gross margin of 35% after cost of sales and direct labour. The policy might define insured gross profit as turnover less purchases only, which could give a rate of 60% or more.
If your broker set the sum insured using the accounts figure, the gap only shows up when you claim. By then it’s too late to fix.
Standard turnover is only the starting point. Most wordings include an adjustments clause, often called the trends clause or other circumstances clause, which allows the figures to be adjusted so they reflect what would have happened had the incident not occurred.
This is where forensic analysis earns its keep. The question is not what you turned over last year. It is what you would have turned over this year, but for the damage. A credible “but for” projection might consider:
Adjustments work both ways. If a major customer gave notice the month before your fire, the insurer will argue standard turnover should come down. A fair projection has to deal with that honestly, or it loses credibility on everything else.
The courts have also limited how far insurers can use trends clauses. In the COVID-19 test case, the Supreme Court held in FCA v Arch Insurance that trends clauses should not be read so as to strip out the effects of the very circumstances that caused the insured loss. The case concerned disease and denial of access cover, but the reasoning still shapes how trend arguments are framed.
The indemnity period starts on the date of the incident and runs until your trading results stop being affected by it, up to the maximum indemnity period in your schedule. Reopening the doors is not the end. If customers drifted to competitors while you were closed, the lost turnover in the months after reopening can still be claimable.
We often see business owners stop collecting evidence once repairs are complete. That’s usually a mistake. Recovery tends to be gradual. A manufacturer may be back in production within weeks but take months to win back the orders that were placed elsewhere. A hospitality business may reopen in spring but miss the summer bookings that would normally have been made months earlier.
The maximum indemnity period matters here too. A 12-month limit can look generous until you factor in planning permission, specialist equipment lead times and the time it takes to rebuild a customer base.
Increased cost of working covers extra spending that is necessary and reasonable to reduce the loss of turnover, such as temporary premises, overtime, hired equipment or outsourcing production. It is usually capped by the gross profit that spending saved, known as the economic limit. Some policies add a separate additional increased cost of working item for spending beyond that limit.
This is where good records make a real difference. Each cost needs to show why it was incurred, what it achieved and how it was approved. “We hired a unit because we had to keep going” is not enough. A forensic accountant will link each cost to the turnover it protected and test it against the economic limit before the adjuster does.
Savings work the other way. If your business rates were reduced, staff were furloughed or utility bills fell while the premises were closed, those savings come off the claim. Leaving them out does not make them disappear. It just hands the adjuster an easy reason to question the rest of your figures.
Here’s a simplified business interruption claim calculation for a manufacturer with a 12-month maximum indemnity period and a fire on 1 March:
| Step | Figure |
|---|---|
| Last financial year turnover | £1,200,000 |
| Uninsured working expenses (purchases) | £480,000 |
| Insured gross profit | £720,000 |
| Rate of gross profit | 60% |
| Standard turnover, March to August last year | £600,000 |
| Trend adjustment for 5% pre-incident growth | £30,000 |
| Adjusted standard turnover | £630,000 |
| Actual turnover, March to August this year | £210,000 |
| Shortfall in turnover | £420,000 |
| Loss of gross profit (£420,000 × 60%) | £252,000 |
| Add: increased cost of working within the economic limit | £40,000 |
| Less: savings in insured costs | (£8,000) |
| Calculated loss | £284,000 |
Now suppose the sum insured was set at £600,000, based on a lower accounts figure. The policy required at least £720,000, being the rate of gross profit applied to annual turnover. Under the average condition, the payment is reduced proportionately: £600,000 ÷ £720,000 = 83.3%.
The claim payment becomes roughly £236,700. That’s around £47,300 lost, not because the loss was overstated but because the sum insured was too low. Some policies use a declaration-linked basis that softens this, so check your schedule before you assume average applies.
The loss adjuster is often supported by their own forensic accountants. Their job is to establish what is properly payable under the policy. That’s not the same as making sure you recover everything you are entitled to.
In our experience, the arguments in a business interruption claim are rarely about the arithmetic. They are about assumptions. Which months are comparable? Was growth real or a one-off? Did a lost customer leave because of the fire or because of pricing? Whoever sets out those assumptions first, with evidence, tends to frame the negotiation.
An independent calculation typically involves:
Many policies include a professional accountants’ clause or claims preparation costs clause, which can cover the cost of producing the figures, usually up to a set limit. It often excludes fees for negotiating the claim, so read the wording carefully.
The strength of your claim depends on the quality of your numbers. Monthly management accounts, VAT returns, payroll reports, sales ledgers and bank statements form the core evidence. If your management accounts are patchy or produced months late, the projection becomes harder to defend. Our guide on how management accounts help SME owners explains what good monthly reporting looks like.
Turnover is normally measured net of VAT for VAT-registered businesses, and it should reconcile to your VAT returns. Any mismatch invites questions.
If your reporting needs strengthening, practical SME accounting and business support now can make a future claim far easier to prove. A review by our internal audit services team can also test whether your business continuity arrangements and records would stand up after a major incident.
Large business interruption claims can take months to settle, and your cash flow doesn’t wait. Request interim payments as soon as there is an agreed minimum loss, and keep a 13-week cash flow forecast running so you can show the insurer and your lender exactly when money is needed.
The law also gives you some leverage. Under section 13A of the Insurance Act 2015, insurers must pay sums due within a reasonable time, including a reasonable time to investigate and assess the claim. Insurers have a defence where there are reasonable grounds to dispute the claim, and business policies can contract out if transparency requirements are met. Damages for late payment must also be pursued within strict time limits.
If delays are pushing the business towards serious cash pressure, speak to our business recovery and restructuring team early. Decisions taken under pressure while waiting for an insurer can be difficult to reverse.
Business interruption proceeds that replace lost trading profit are generally treated as taxable trading income in the UK, so build that into your forecasts. Proceeds for damaged plant and machinery are a separate matter and can affect your capital allowances pools. Our capital allowances and specialist tax advice team can help you plan the tax treatment of replacement assets.
There’s also the question of when to recognise an insurance receivable in your accounts. That depends on how certain the recovery is at the balance sheet date, and it is something your external audit team will look at closely.
Most UK policies use gross profit as defined in the policy, which is usually turnover less uninsured working expenses such as purchases. Because wages and fixed overheads are normally included, insured gross profit is higher than accounting gross profit. Some policies use gross revenue or other bases instead, so check your schedule.
Usually yes, indirectly. Under a typical gross profit policy, wages are not treated as an uninsured working expense, so they sit within insured gross profit and the claim helps fund them. Some policies treat payroll differently or insure it separately, which can change the calculation significantly.
It depends on the length of the indemnity period, the complexity of the business and the quality of the records. Many claims cannot be finalised until the indemnity period ends, which can take a year or more. Interim payments can bridge part of the gap.
Yes. Your own accountant or an independent forensic accountant can prepare the figures, and many policies contribute towards those costs under a claims preparation clause. Independent forensic support is particularly useful where the loss is large or the trend adjustments are likely to be disputed.
A business interruption claim is won on evidence. The sooner your calculation is built properly, the less room there is for assumptions that cost you money.
SCC’s forensic team has more than 25 years of experience in loss quantification and financial disputes across Northern Ireland, Ireland and the UK. If you are preparing a claim, or think an offer undervalues your loss, speak to our forensic accounting services team for a confidential review of the policy, the figures and the assumptions behind them.
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