Most UK small business failures are profitable on paper. The thing that ends them is cash. Cash and profit aren’t the same, and the gap between them is where new businesses get caught. This guide walks through what cash flow actually means in practical terms, why it diverges from profit, and the small habits that prevent the most common cash crises in your first 24 months.
Profit vs cash — the basic distinction
Profit is revenue minus expenses, calculated when invoiced or incurred – the accruals basis. Cash is actual money in your bank account, calculated when received or paid – the cash basis. A business can be profitable on paper and still run out of cash. The most common reason is timing: customers pay slowly, suppliers must be paid quickly, and the working capital gap between the two has to come from somewhere.
The cash flow gap
A worked example. Customer A signs a £20,000 contract on Day 1. You incur costs of £8,000 delivering it across Days 1–30. You invoice on Day 30, payment terms net-30. Customer pays on Day 60. Across Days 1–60 you’ve spent £8,000 cash and received £0. That £8,000 gap has to come from somewhere – your savings, a director’s loan, an overdraft, or supplier credit. The bigger you grow, the bigger the gap, even though each contract is profitable.
The hidden tax cash drains
VAT collected from customers is not yours – it’s HMRC’s in transit through your business. Keep it separate. Corporation Tax accrues during the year and is payable 9 months and 1 day after the period end . PAYE and NIC for employees due monthly. Set aside cash for these as you go, not at year-end – the VAT bill at 20% of turnover will absorb every penny of margin if you spent it like income.
The 13-week rolling cash flow
The single most useful tool for a small business. Forecast cash in and cash out, week by week, for the next 13 weeks. Update weekly with actuals. The 13-week window is long enough to see meaningful issues and short enough to be accurate. You spot cash crunches 4–8 weeks ahead, with time to act – chase debtors, defer suppliers, raise finance – rather than discovering them on payday.
Habits that protect cash
Invoice the day work is delivered. Take 30–50% deposits on new client work. Net-14 or net-30 payment terms, not net-60+. Direct debit retainer clients where possible. Hold a tax savings account for VAT, Corporation Tax and payments on account. Hold a buffer account with 1–3 months of operating costs. None of this is exotic; the discipline of doing them all consistently is what separates founders who sleep well from founders who don’t.
Common cash mistakes new founders make
Treating revenue as cash (it isn’t, until paid). Forgetting VAT is collected, not earned. Drawing too much salary or dividend too early in the company’s life. Spending future revenue – a signed contract isn’t paid revenue. No buffer for late-paying clients. Not separating tax money from operating money. Each of these is a textbook recipe for the “profitable on paper, broke in the bank” failure mode.
When you run short of cash — options
In rough order of preference. Chase outstanding invoices aggressively (see our late-paying clients guide). Negotiate longer terms with suppliers (B2B almost always possible). Defer non-essential costs. Bridging finance: invoice factoring, business overdraft, business credit card. Time to Pay arrangements with HMRC for tax bills. Director’s loan to the company with proper paperwork. The first three are free; the rest cost interest, fees, or relationship goodwill.
Cash forecasting tools
For under 5 employees, a 13-week rolling spreadsheet template is usually enough. Above that, accounting software with cash flow features pays back quickly – FasCash, Xero, FreeAgent, QuickBooks. Direct bank-feed integration via Open Banking is essential; manual entry doesn’t get done, which means the forecast is permanently a week stale and stops being trustworthy.
A simple monthly cash routine
On the 1st of every month, 30 minutes. Download last month’s bank statement and reconcile. Update the 13-week forecast with actuals. Identify any crunches in the next 8 weeks. Set aside tax money to the savings account. Review aged debtors – chase any over 14 days late. That’s the rhythm. Once it’s habitual, cash management stops being a fire-fighting exercise.
Frequently asked questions
The questions UK small businesses ask most often about cash flow.
How much cash buffer should a small business hold?
Industry rule of thumb: 1-3 months of operating expenses in a separate buffer account. New service businesses can sometimes get by with less; product or stock-heavy businesses need more. The goal is enough that a single late-paying customer or surprise expense doesn't trigger a panic.
I'm registered for VAT. How should I handle the VAT money?
Open a separate savings account and transfer 20% (or your appropriate VAT rate) of every customer payment into it the day it lands. When the VAT return is due, the money is sitting there. Do NOT spend VAT money as if it were your own — it's HMRC's, in transit through your business.
What's a 13-week rolling cash forecast?
A spreadsheet (or report in your accounting software) showing expected cash in and cash out for each of the next 13 weeks. Updated weekly with actuals. The 13-week window is short enough to be accurate and long enough to spot crunches with time to act. The single most useful tool for small business cash management.
My profit and loss says I made £30k profit. Why is my bank balance £5k?
Cash and profit diverge for several reasons: (a) customers haven't paid yet (debtors), (b) you've paid suppliers but not yet invoiced clients (work in progress), (c) you've taken director's drawings, (d) tax hasn't been paid yet but is accrued, (e) you've bought equipment (capital expense, not P&L expense). Sit down with your accountant or bookkeeping software and reconcile.
Should I pay my director's salary or dividend monthly or quarterly?
Monthly for salary if it gives the appearance of a 'real' employer (helps with mortgage applications). Quarterly or even annually for dividends — only pay them when the company has the cash. Salary is contractual; dividends are discretionary.
Can I take more salary than the company is making in a month?
For limited companies, you can take a salary regardless of monthly profit (it's a deductible expense), but if it persistently exceeds the cash you're generating, you'll deplete the bank balance. For dividends, you must pay them out of distributable profits — if the company hasn't accumulated enough, you can't legally declare them.
What's the difference between an invoice and cash collected?
Invoice = you've billed the client; cash collected = they've paid. The gap between the two is your 'debtor days' — the average time between invoicing and getting paid. Most UK small businesses run 30-45 debtor days. Less is better; more is a cash flow problem.
When should I worry about cash flow vs ignore it?
Always have a cursory monthly view (15 minutes — bank balance, recent invoices, upcoming payments). Worry actively when the 13-week forecast shows a negative cash position, when debtors days are climbing, or when you're consistently funding the business from your personal account. Never let it become a year-end surprise.
