Profitable businesses run out of money. It happens often enough that it should not surprise anyone, and yet it catches owners out every year, usually in the month they were feeling most pleased with the accounts. Profit is an opinion shaped by accounting rules. Cash is a fact you can check on your banking app.
The gap between them has two causes: timing, and the things that move cash without ever appearing in your profit figure. Understanding both is one of the highest-value things an owner can learn, because a business that fails while profitable has almost always failed on timing rather than on trading.
Why do profit and cash diverge?
Profit is recorded when you raise the invoice. Cash arrives when the customer decides to pay it, which might be sixty days later, or ninety, or after three phone calls. A business growing quickly invoices more, so its profit rises, while the cash for that work sits in someone else's bank account.
Then there are the things that consume cash but never touch the profit and loss: stock you have bought but not sold, a van bought outright, loan capital repayments where only the interest is an expense, VAT and PAYE you have collected on HMRC's behalf and are simply holding, and a corporation tax bill for a year that already feels like history. None of that appears as a cost in your profit figure. All of it takes cash out of the account.
Why growth is usually the culprit
This is the cruel part. The faster a business grows, the more cash it consumes. More work means more stock, more wages and more materials, all paid before the customer pays you. An owner who wins a large new contract can be more profitable and closer to running out of money in the same quarter.
Put numbers on it. Illustrative arithmetic: you win £100,000 of extra work at a 40 per cent gross margin. The £60,000 of materials and labour goes out over the first month or two. The customer pays sixty days after invoice. Profit says you made £40,000. The bank says you were £60,000 down for two months before any of it came back, and if you fund that from the current account rather than deliberately, the good news and the tight month arrive together.
The number that explains it
The cash conversion cycle is the honest measure: how many days pass between money leaving your business and coming back. Debtor days plus stock days, minus creditor days.
If customers take 60 days to pay, stock sits for 30 days, and you pay suppliers in 30 days, your cycle is 60 days. Every pound of growth needs funding for two months. Shorten that cycle and the business funds its own growth. Lengthen it and growth has to be borrowed for — which is a decision worth making deliberately rather than discovering.
How to use this model
Look at both numbers every month
Profit and closing cash, side by side, on the same page. When they move in opposite directions, find out why before it becomes a pattern.
Work out your cash conversion cycle
Debtor days plus stock days minus creditor days. Know the number, then set a target to cut it. Ten days off the cycle is real money released from the business without selling anything extra.
Attack debtor days first
It is usually the cheapest win. Invoice the day the work completes rather than at month end, state terms plainly on the invoice, and chase on a schedule rather than when it occurs to you.
Ring-fence the tax money
VAT and PAYE are not your money. A separate account removes the single most common cash shock in a small business, and it costs nothing but the discipline of a standing transfer.
Build a rolling 12-week cash forecast
Not an annual one. Twelve weeks is close enough to be accurate and far enough ahead to act, and it is the only forecast most owners will actually keep updated.
Model the growth before you take it
Before accepting a large contract, work out the cash it consumes before it pays, and where that funding comes from. Some good work is simply not affordable yet, and knowing that in advance is a commercial decision rather than a crisis.
The mistake most owners make
Reading the profit figure as a description of the bank balance. They answer different questions: profit tells you whether the trading model works, cash tells you whether the business survives the next eight weeks. Both are necessary and neither substitutes for the other.
The second mistake is treating a cash squeeze as a sales problem. Selling more into a long cash conversion cycle makes the squeeze worse before it makes it better, which is why owners sometimes work their hardest quarter and end it with less in the bank than they started.
Questions to ask yourself
- Out of 10, how confident are you that you could explain why your profit and your bank balance disagree this month?
- How many days does it take, on average, from paying for something to being paid for it?
- If your best customer paid 30 days later than usual, how long could the business carry that?
- What would change in how you run the business if you watched cash as closely as you watch sales?
The takeaway: most owners do not have a profit problem. They have a timing problem that only shows up as a cash problem, usually too late to fix calmly. Know your cash conversion cycle and the timing stops being a surprise.
Where this fits
This is the heart of Financial Coaching — regular sessions that build real confidence with the numbers, delivered with Buzz Accounting so the figures in front of you are current rather than remembered. Coaching is not regulated financial advice; it is help understanding and running your own numbers. Pair it with The Product Ladder, since continuity revenue is the cheapest cure for a lumpy month, and with Project Management and Scope, where job margin quietly leaks.
Get the next one in your inbox
One practical, plain-English guide for business owners each week. No spam, unsubscribe any time.
Common questions
How can a profitable business run out of money?
Because profit and cash answer different questions. Profit is recorded when you raise the invoice; cash arrives when the customer pays, which may be sixty or ninety days later. On top of that, several things drain cash without ever appearing as a cost in your profit figure: stock bought but not sold, equipment bought outright, the capital element of loan repayments, VAT and PAYE you are holding for HMRC, and last year's corporation tax bill. A business can therefore be trading well, showing a healthy profit, and still be unable to clear payroll in a particular week. That is a timing problem, not a trading one.
What is the cash conversion cycle and how do I work mine out?
It is the number of days between money leaving your business and coming back: debtor days plus stock days, minus creditor days. If your customers take sixty days to pay, stock sits for thirty, and you pay suppliers in thirty, your cycle is sixty days, which means every pound of growth needs funding for two months. Work it out from your own figures once, then set a target to reduce it. Debtor days are usually the cheapest to attack: invoice the day the work completes rather than at month end, state terms plainly, and chase on a schedule rather than when it occurs to you.
Should I keep VAT and PAYE in a separate bank account?
It is one of the simplest protections available to a small business, and it costs nothing but the discipline of a standing transfer. VAT and PAYE are collected on HMRC's behalf, so they were never your money, yet they sit in the current account looking like working capital and get spent on materials or wages in a tight month. A separate account removes the most common cash shock owners run into, because the quarterly bill stops competing with everything else for the same balance. Pair it with a rolling twelve-week cash forecast so the payment dates are visible before they arrive rather than after.