How Can Sales Growth Create a Working-Capital Gap?
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TL;DR
Sales growth can create a working-capital gap when suppliers and stock must be paid before customers pay. In our 12-month illustration, sales rise from £100,000 to £210,000 a month and generate £318,000 of simplified operating profit. Yet £40,000 of opening cash is not enough: the month-end balance falls to minus £17,000 in month 6 because customer cash arrives 60 days after sale while stock is paid for one month before sale.
Profit can rise while the bank balance falls
Profit records revenue and costs when they are earned or incurred. Cash records when money actually reaches or leaves the bank. Growth pulls those two measures apart when a business pays for stock, labour or delivery before its customers pay.
Our illustration uses a UK wholesaler with £40,000 in opening cash. Monthly sales rise from £100,000 to £210,000 over a year. The business earns a 30% gross margin and pays £20,000 of fixed operating costs each month. It is profitable in every month.
The awkward part is timing. Customers pay 60 days after sale. Stock is ordered two months before sale and paid for 30 days after ordering, so the supplier cash leaves one month before the related sale. The business therefore pays for month 6 stock in month 5 and collects the month 6 sale in month 8.
That lag produces £318,000 of simplified operating profit over the year, but cash falls below zero in month 3 and reaches a low of minus £17,000 in month 6. The business needs £57,000 of opening cash to keep every month-end balance at or above zero: £17,000 more than it has.
Every figure is an editorial assumption in pounds sterling, excluding VAT. This is a worked model, not a sector average, forecast or claim about a real company.
Download the 12 monthly rows as CSV.
The assumptions behind the £17,000 gap
The model starts with an established sales pipeline rather than pretending a trading business appears from nowhere in month 1.
| Input | Assumption |
|---|---|
| Opening cash | £40,000 |
| Sales | £100,000 in month 1, rising by £10,000 a month to £210,000 |
| Sales before the model starts | £80,000 two months earlier; £90,000 one month earlier |
| Month 13 sales used for the final stock payment | £220,000 |
| Gross margin | 30% |
| Cost of stock | 70% of the related sale |
| Fixed operating costs | £20,000 a month |
| Customer payment timing | 60 days after sale |
| Stock timing | Ordered two months before sale |
| Supplier payment timing | 30 days after order, one month before sale |
The sales path is deliberately brisk: annual revenue is £1.86 million, and the monthly run rate more than doubles. That is useful for exposing the working-capital effect. It is not presented as typical growth.
The 30% gross margin means a £100,000 sale carries £70,000 of stock cost. If your margin is quoted as markup instead, convert it before using the model. A 30% margin is not a 30% markup; the margin and markup calculator shows the difference.
The simplified monthly profit calculation is:
Operating profit = sales × 30% − £20,000
The monthly cash calculation is:
Net cash flow = customer receipts − supplier payments − £20,000
Those formulas use the same trading activity. They place it in different months.
The month-by-month result
| Month | Sales | Simplified profit | Customer receipts | Supplier payment | Net cash flow | Closing cash |
|---|---|---|---|---|---|---|
| 1 | £100,000 | £10,000 | £80,000 | £77,000 | −£17,000 | £23,000 |
| 2 | £110,000 | £13,000 | £90,000 | £84,000 | −£14,000 | £9,000 |
| 3 | £120,000 | £16,000 | £100,000 | £91,000 | −£11,000 | −£2,000 |
| 4 | £130,000 | £19,000 | £110,000 | £98,000 | −£8,000 | −£10,000 |
| 5 | £140,000 | £22,000 | £120,000 | £105,000 | −£5,000 | −£15,000 |
| 6 | £150,000 | £25,000 | £130,000 | £112,000 | −£2,000 | −£17,000 |
| 7 | £160,000 | £28,000 | £140,000 | £119,000 | £1,000 | −£16,000 |
| 8 | £170,000 | £31,000 | £150,000 | £126,000 | £4,000 | −£12,000 |
| 9 | £180,000 | £34,000 | £160,000 | £133,000 | £7,000 | −£5,000 |
| 10 | £190,000 | £37,000 | £170,000 | £140,000 | £10,000 | £5,000 |
| 11 | £200,000 | £40,000 | £180,000 | £147,000 | £13,000 | £18,000 |
| 12 | £210,000 | £43,000 | £190,000 | £154,000 | £16,000 | £34,000 |
| Total | £1,860,000 | £318,000 | £1,620,000 | £1,386,000 | −£6,000 | £34,000 |
Fixed operating costs of £20,000 a month are included in net cash flow but not repeated in the table. Supplier payments relate to the following month's sales. The month 12 payment therefore funds stock for the assumed £220,000 of month 13 sales.
The cash low occurs before the largest profit months. By month 10, customer receipts have caught up enough for the balance to turn positive again. That recovery does not make the month 3 to month 9 shortfall imaginary. Wages and suppliers still need paying while the spreadsheet waits for month 10.
The British Business Bank says that an otherwise profitable, high-growth company may run out of cash as inventory and receivables increase. Its working-capital guidance also links the capital needed to the time between incurring costs and getting paid.
Where the £324,000 profit-to-cash difference goes
The model's annual profit is £318,000. Its annual net cash flow is minus £6,000. The £324,000 gap is explained by the increase in stock and customer balances created by growth.
Receivables at the start are £170,000: the £80,000 and £90,000 sales waiting to be collected. At the end, the final two months of sales are still unpaid, totalling £410,000. Receivables have increased by £240,000.
Paid-for inventory rises from £70,000 for month 1 sales to £154,000 for the assumed month 13 sales. That is another £84,000 tied up.
| Working-capital movement | Increase |
|---|---|
| Customer receivables | £240,000 |
| Paid-for inventory | £84,000 |
| Total additional cash tied up | £324,000 |
Subtract £324,000 of additional working capital from £318,000 of simplified profit and the result is the model's £6,000 cash outflow. No mystery, and no missing bag of money. The sales are profitable; the cash attached to them has not completed the trip.
The British Business Bank's separate cash-flow guide defines profit and cash flow differently and notes that growth can require stock and customer credit. That supports the mechanism. The £324,000 result is our calculation from the disclosed assumptions, not a figure taken from the guide.
Payment terms change the answer sharply
We reran the same growth path with customers paying in 30 days. We also tested flat monthly sales of £100,000 with 60-day customer terms. Margin, fixed costs, supplier timing and opening cash stayed unchanged.
| Scenario | Annual profit | Annual net cash flow | Minimum opening cash | Lowest balance with £40,000 opening cash |
|---|---|---|---|---|
| Flat £100,000 monthly sales; customers pay in 60 days | £120,000 | £120,000 | £0 | £50,000 |
| Growth; customers pay in 30 days | £318,000 | £114,000 | £12,000 | £28,000 |
| Growth; customers pay in 60 days | £318,000 | −£6,000 | £57,000 | −£17,000 |
Cutting the assumed customer wait from 60 days to 30 reduces the minimum opening cash from £57,000 to £12,000. The £40,000 opening balance then remains positive throughout.
That comparison is not an instruction to impose 30-day terms on every customer. Commercial bargaining power, customer quality and actual payment behaviour vary. It shows why a sales forecast without collection dates is only half a forecast. Business.gov.uk recommends including outgoing spend, incoming revenue and expected payment dates when assessing whether funding will cover a gap; its cash-flow guidance is written for exporters, but the timing principle is broader.
If customers miss the agreed date, the gap widens again. Our UK late-payment cost analysis deals with the financing and administrative cost of overdue invoices. This model sticks to the stated 60-day term and assumes every customer pays on time.
Build your own growth cash-flow model
Start with dates, not annual totals.
- Put each month's sales in the month when the sale is earned.
- Move the cash receipt to the month when customers are expected to pay. Use actual collection history where you have it.
- Put stock, subcontractor and delivery payments in the months when cash leaves the bank. Do not automatically align them with the sale.
- Add payroll, rent, software, insurance, tax, debt payments, capital expenditure and owner withdrawals on their expected dates.
- Calculate the running cash balance and find the lowest point.
- Repeat the model with slower collections, weaker margin, faster growth and a missed sales target.
The minimum opening cash is the amount required to lift the lowest cumulative balance to zero. Zero is not a sensible operational target. Add room for within-month timing, forecast error and costs the model does not contain.
Our cash-buffer analysis shows how three different trading patterns change the reserve needed under a shock. The cash runway calculator is useful for a flat monthly burn. It deliberately assumes stable revenue and expenses, so it cannot see the rising stock and receivables in this growth case.
What the model leaves out
The figures exclude VAT, corporation tax, payroll taxes, bad debts, discounts, returns, financing costs, capital expenditure, depreciation and dividends. All movements are placed at month-end, so the model can miss a within-month shortage. Its simplified profit is gross profit less one fixed operating-cost line, not a set of statutory accounts.
Supplier credit is represented by the stated payment date rather than a separate accounts-payable balance. The model assumes stock is sold as planned, customers pay exactly on time and the 30% margin holds as volume rises. A discount used to win growth would reduce both profit and cash.
It also assumes the business can order exactly the stock needed. Minimum order quantities, safety stock and slow-moving inventory could increase the requirement. A service business with little inventory would have a different pattern, although payroll paid before customer collection can create the same sort of gap.
If the forecast shows a shortfall, first check whether the growth is genuinely profitable and whether collections, purchasing or supplier timing can improve. If finance still has a job to do, model its repayments in the same cash forecast. The £50,000 business-loan cost analysis explains how rate and fee treatment change the cash received and repaid, while the business loan calculator can test the terms in an actual offer. Borrowing can bridge a timing gap. It cannot rescue a sale that loses money each time it repeats.
Frequently asked questions
Can a profitable business run out of cash because it grows too quickly?
Yes. If each new sale requires stock, labour or delivery cash before the customer pays, faster growth can increase the funding gap. Profitability helps only after enough of that cash has completed the cycle.
How much working capital does growth require?
There is no reliable percentage of sales that works for every business. Build a dated cash forecast, find its lowest cumulative balance and test slower customer payments, inventory changes and supplier terms. The result is a minimum for those assumptions, not a guarantee.
Is gross margin the same as cash available to pay overheads?
No. Gross margin measures sales less the direct cost assigned to those sales. Cash may still be tied up in unpaid invoices or stock, and overheads, tax, debt payments and capital spending can leave separately.
What happens if customers pay in 30 days instead of 60?
In this illustration, the minimum opening cash falls from £57,000 to £12,000. That is a model result, not a promise: the effect in your business depends on sales, margin, stock timing and whether customers meet the terms.
Should a business borrow to fund growth?
Possibly, but only after checking the margin, the cash cycle and the downside case. Compare the amount actually advanced, fees, security, repayment dates and total cost. Put every repayment into the forecast before accepting the facility.
Test a business-loan repayment
ContinueSources and methodology
Illustrative 12-month GBP model for an established wholesaler. Monthly sales rise from £100,000 to £210,000, gross margin is 30%, fixed operating costs are £20,000 a month, customers pay 60 days after sale, and stock is ordered two months before sale and paid for 30 days later. The model compares simplified operating profit with month-end cash, then reruns the growth path with 30-day customer terms and a flat-sales baseline. All figures are editorial assumptions excluding VAT, not observed business averages or advice.
- British Business Bank. Working capital: why it’s important to your business - checked 26 October 2026
- British Business Bank. What is cash flow and how do you manage it? - checked 26 October 2026
- Department for Business and Trade / Business.gov.uk. Avoid cashflow challenges when exporting - checked 26 October 2026
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