Working capital explained (the money your business needs to breathe)

What working capital actually is

Working capital is the everyday money tied up in keeping your business running day to day.

It's not the same as the cash in your bank account, and it's not your profit. It's the pool of short-term money your business needs sloshing around just to operate — to buy stock, wait for customers to pay, and settle your own bills on time. Get this pool right and the business runs smoothly. Get it wrong and a profitable business can find itself gasping for air.

Here's the metaphor that makes it click: working capital is your business's breathing room. Air comes in, air goes out, and as long as there's enough in your lungs at any moment, you're fine. Working capital is the financial equivalent — money flowing in from customers, money flowing out to suppliers, and enough in the system at all times that you never find yourself short of breath when a bill lands. A business with healthy working capital breathes easily. One that's run it too tight is permanently a little winded, always one slow payment away from a panic.

What's in the pool (and what comes out)

Working capital is made of short-term things — money and stuff that turns into cash, or has to be paid out, within roughly the next year. There are three pieces.

What you're owed. The money customers have promised but haven't paid yet — your accounts receivable (money owed to you). It's yours, it's coming, but it's not in your account today. It's air on its way in.

Your stock. If you sell physical things, the goods sitting in your cupboard or warehouse are part of your working capital, because they'll soon turn into sales and then into cash. (Service and software businesses often have little or no stock, so they can skip this one.)

What you owe. The bills, supplier invoices, VAT and short-term debts you'll have to pay soon — your accounts payable (money owed by you). This is air on its way out.

Put them together and you get the whole picture:

Working capital = (what you're owed + your stock) − what you owe.

In plain English: take everything that's about to turn into cash, subtract everything that's about to demand cash, and what's left is your breathing room.

A simple example

Let's make it real. Say you run a small business that sells and fits flooring.

What's about to turn into cash:

• £12,000 that customers owe you for jobs already done
• £8,000 of flooring stock sitting in your storeroom

That's £20,000 heading towards becoming cash.

What's about to demand cash:

• £6,000 you owe suppliers for materials
• £2,000 of VAT due to HMRC soon

That's £8,000 going out.

Your working capital is:

£20,000 − £8,000 = £12,000.

That £12,000 is positive, which is the comfortable place to be — you've got more coming in than going out in the short term, so you can breathe. If the sum had come out negative — more owed than owned in the short term — that's the warning sign that you might struggle to cover your bills as they fall due, even if the business is profitable overall.

Positive, negative, and why it's not always bad to be tight

Positive working capital means you've got a cushion: more short-term assets than short-term bills. For most small businesses, that's what you want — room to absorb a late-paying customer or an unexpected cost without scrambling.

Negative working capital sounds alarming, and often it is a red flag — it can mean you're heading for a cash squeeze. But not always. Some businesses run on negative working capital perfectly happily because their customers pay before they have to pay their own suppliers — think a busy café that takes cash at the till today but pays its food supplier next month. For them, customers' money funds the business.

The point isn't to chase a particular number. It's to know yours, understand which side of the line you're on, and make sure it's deliberate rather than a nasty surprise. A founder who knows their working capital knows whether the business can breathe through a slow month. A founder who doesn't is holding their breath and hoping.

Why working capital catches profitable founders out

This is the part worth burning into memory: you can be profitable and still run out of breath.

It happens like this. You win great work, you invoice for it, your profit on paper looks healthy. But the customers haven't paid yet, your suppliers want their money now, and the VAT bill is due. On paper you're winning. In the bank, you're suffocating. That gap — profit you've earned but can't yet touch — is a working-capital problem, and it's one of the most common ways a growing, healthy-looking business gets into trouble.

In fact, growth itself eats working capital. The faster you grow, the more stock you buy and the more work you deliver upfront before customers pay — so the more money gets tied up in the pool, and the tighter your breathing gets, even as the business booms. It's the cruel twist that surprises founders: success can starve you of cash if you're not watching your working capital. (See: Profit vs cash — why you can be profitable and still broke.)

This is exactly why working capital lives on your balance sheet alongside everything you own and owe — it's one of the clearest signals of whether the business can actually keep operating, not just whether it's profitable on paper. (See: What is a balance sheet?)

How to keep your breathing easy

You don't manage working capital with a spreadsheet and a furrowed brow. You manage it with a few simple habits.

Get paid faster. The biggest lever is usually your accounts receivable. Invoice promptly, set short payment terms, chase overdue invoices politely but persistently, and ask for deposits on big jobs. Every invoice you turn into cash sooner is more air in your lungs.

Don't over-stock. Money sitting as stock is money you can't use. Buy what you'll actually sell soon, rather than tying up your breathing room in a cupboard full of goods.

Use your supplier terms sensibly. If a supplier gives you 30 days to pay, there's no need to pay on day one. Holding onto your cash a little longer (without ever paying late) keeps more in the pool.

None of this requires accounting skill. It's just keeping an eye on what's coming in versus what's going out — the same calm glance you'd give any of your key numbers.

The short version

Working capital is the everyday money tied up keeping your business running — what you're owed plus your stock, minus what you owe in the short term. Positive means breathing room; negative is usually a warning, though some businesses run on it deliberately. It's how a profitable business can still gasp for cash, especially while growing. Know yours, get paid faster, and you'll keep breathing easily.

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Ready to stop holding your breath? In Ledgers, the money owed to you, the bills you owe and your overall position are tracked automatically from your bank feed and invoices — so you can see your breathing room at a glance, without building a spreadsheet or learning accounting. See your numbers without learning accounting → start free.

To see where working capital fits in the bigger picture: What is a balance sheet? →

And the number that tells you how long your cash lasts: What is runway and how do I work out mine? →

Frequently asked questions

What is working capital in simple terms?

It's the short-term money your business needs to keep running — what customers owe you plus your stock, minus what you owe suppliers and HMRC soon. It's your breathing room: enough flowing through the system to cover bills as they fall due.

How do I calculate working capital?

Add up your short-term assets (money owed to you plus stock) and subtract your short-term liabilities (bills, supplier invoices and tax due soon). If you're owed £20,000 and owe £8,000, your working capital is £12,000.

Is negative working capital always bad?

Not always. It can signal a cash squeeze, but some businesses — like cafés or shops paid at the till before they pay suppliers — run on negative working capital deliberately. The key is to know your position and make sure it's intentional.

Why can a profitable business run out of cash?

Because profit on paper isn't cash in the bank. If customers haven't paid but your bills are due, you can be profitable and still short of money — a classic working-capital squeeze, made worse by fast growth tying up cash in stock and unpaid invoices.

See your numbers without learning accounting

Ledgers does the bookkeeping — bank feeds, VAT, year-end — and keeps your accountant in the loop. Free for pre-revenue founders.

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