You have found bigger premises, the landlord wants a five-year lease, and your sales forecast says you will hit £500,000 in year one. The lease looks affordable on paper. But what happens if sales come in 20 per cent lower than forecast? Will you still be able to cover the rent, the business rates, and the extra staff you have hired for the bigger space? This is the exact moment sensitivity analysis earns its keep. It will not tell you whether to sign the lease — but it will tell you exactly how much room for error you have, and whether that room is big enough to sleep at night.
What Sensitivity Analysis Actually Means
Strip away the jargon and sensitivity analysis is simply this: you take a forecast built on assumptions, and you ask ‘what if one of those assumptions is wrong?’. Your £500,000 sales figure is not a fact — it is a guess, dressed up in a spreadsheet. Sensitivity analysis forces you to test that guess by deliberately plugging in worse numbers and seeing what happens to profit and cash. It is the financial equivalent of asking ‘what is the worst that could realistically happen, and can I survive it?’ before you sign anything with a five-year commitment attached.
The reason this matters so much with a lease is that rent is a fixed cost. Unlike stock or casual labour, you cannot turn it off if sales disappoint. Sensitivity analysis shines a light on exactly where your fixed costs stop being affordable, so you negotiate the lease terms — length, break clauses, rent-free periods — with your eyes open rather than hoping for the best.
The Scenario: A New Premises and a £500,000 Sales Forecast
Let us put real numbers around this. A retail business currently trades from a small unit, turning over £350,000 a year. A larger unit has become available, and the owner believes the extra space and footfall will push sales up to £500,000. The new lease is £48,000 a year (£4,000 a month), on a five-year term with no break clause. Combined with the extra business rates, utilities, and one additional part-time member of staff, total fixed costs in the new premises rise to £165,000 a year, up from £120,000 in the old unit. Gross margin on sales is a steady 45 per cent across both locations, meaning cost of sales runs at 55 per cent of revenue.
Building the Base Case
Before stress-testing anything, we need the base case — the profit the business expects if the £500,000 forecast is accurate.
| Forecast sales revenue | £500,000 |
| Cost of sales (55% of revenue) | £275,000 |
| Gross profit (45% margin) | £225,000 |
| Fixed costs in new premises (incl. lease of £48,000) | £165,000 |
| Net profit (base case) | £60,000 |
On the face of it, £60,000 of profit looks like a healthy return and plenty of cushion to cover a five-year lease. But that number only holds if the £500,000 sales forecast is correct. The real question is: what does profit look like if the forecast is optimistic — which most sales forecasts, if we are honest, tend to be?
Stress-Testing the Forecast: Three Scenarios
Sensitivity analysis means running the same calculation again, but with sales 10 per cent, 20 per cent, and 30 per cent lower than forecast, while fixed costs stay the same — because the lease, rates, and extra staff cost the same whether or not customers walk through the door.
| Scenario | Sales revenue | Gross profit (45%) | Fixed costs | Net profit / (loss) |
|---|---|---|---|---|
| Base case (forecast) | £500,000 | £225,000 | £165,000 | £60,000 |
| 10% below forecast | £450,000 | £202,500 | £165,000 | £37,500 |
| 20% below forecast | £400,000 | £180,000 | £165,000 | £15,000 |
| 30% below forecast | £350,000 | £157,500 | £165,000 | (£7,500) |
Notice something important here. The ‘30 per cent below forecast’ scenario is not a far-fetched disaster — it is simply the business achieving the same £350,000 of sales it already generates in its current premises. In other words, if the move to bigger premises does not actually grow sales at all, the business tips into a loss of £7,500 a year, purely because fixed costs have risen by £45,000 to pay for space it is not using productively.
What This Means for the Lease Decision
Sensitivity analysis also lets us calculate the breakeven sales figure — the exact revenue needed to cover the new fixed costs, with nothing left over. That is fixed costs divided by gross margin: £165,000 ÷ 45% = £366,667. Below that figure, the business loses money every month it stays in the new unit.
The breakeven point for this lease is £366,667 in annual sales. Current trading is £350,000. That means the business needs sales to grow by at least 4.8 per cent just to break even in the new premises — and the forecast assumes growth of 42.9 per cent. The gap between ‘just surviving’ and ‘the forecast’ is enormous, and that gap is exactly what sensitivity analysis exposes before the lease is signed.
This does not automatically mean the lease is a bad idea. Bigger premises might genuinely drive the footfall and sales growth the owner expects. But it does mean the decision should not rest on the single £500,000 figure. It should rest on an honest view of how likely the business is to clear £366,667 even in a slow year, and what the owner will do if sales stall closer to current levels for the first twelve months while the new location beds in.
Watch out for three common mistakes when stress-testing a forecast like this. First, do not assume costs stay perfectly fixed — stock purchases and part-time hours often flex a little with sales, so a pure worst-case scenario should also trim variable costs slightly. Second, do not sign a long lease without a break clause if your sensitivity analysis shows a loss scenario is plausible; a three-year break option, even at a slightly higher rent, buys you an exit if growth does not materialise. Third, remember rent is usually payable quarterly in advance, so cash flow can be tighter than the annual profit figure suggests, even in a profitable scenario.
On the tax side, there is a small silver lining. Rent paid under an operating lease is a normal deductible expense for corporation tax purposes, reducing taxable profit pound for pound, so the £48,000 annual rent genuinely lowers the tax bill as well as the pre-tax profit. If the business is VAT registered and the landlord has opted to tax the property, VAT will be charged on top of the rent, but this is normally recoverable in full if the premises are used for taxable trading activities — worth confirming before signing, as it affects the cash flow of each quarterly payment even though it does not affect profit.
Recording the Lease Once You Sign
Once the lease begins, the accounting entry for eligible micro-entities is straightforward. Under FRS 105 (the micro-entities regime, which businesses of this size qualify for), an operating lease is simply expensed as the rent falls due, rather than capitalised on the balance sheet. The first month’s payment is recorded like this:
| Account | Dr | Cr |
|---|---|---|
| Rent and rates (profit and loss account) | £4,000 | |
| Bank | £4,000 |
Recording the first month’s rent on the new lease, expensed as incurred under FRS 105 (micro-entities regime). No lease asset or liability is recognised on the balance sheet for a straightforward operating lease under this standard.
If the business instead reports under FRS 102 (including Section 1A for small entities) following the Periodic Review 2024 amendments, or under IFRS 16, this treatment changes. Under revised FRS 102 Section 20, lessees must recognise the lease on the balance sheet as a right-of-use asset and matching lease liability. For an eligible business reporting under FRS 105, however, the simple expense entry above remains applicable.
Key Takeaways
- Never commit to a fixed cost like a lease based on a single sales figure — always run the forecast at 10 per cent, 20 per cent, and 30 per cent below expectations to see where profit turns into loss.
- Calculate your breakeven sales figure (fixed costs divided by gross margin percentage) and compare it honestly to your current trading level, not just your optimistic forecast.
- Negotiate a break clause or shorter initial term if your stress test shows a realistic scenario tipping into a loss — flexibility is worth more than a slightly lower headline rent.
- Remember that rent is tax-deductible and VAT may be recoverable, but these reduce the pain rather than remove the risk, so build them into your cash flow planning, not just your profit forecast.
Want help stress-testing your own numbers before you sign?
Our team helps SME owners turn sales forecasts into realistic, tested plans before major commitments like leases, hires, or new sites. We will build the scenarios, check the breakeven point, and explain what it means for your business in plain English.
