Working capital is current assets minus current liabilities. It is the short-term financial cushion that funds your day-to-day operations: paying suppliers, staff, and tax while you wait for customers to pay you. Positive working capital is the norm for healthy businesses; negative working capital can be a warning sign or, occasionally, a deliberate strategy. The cash conversion cycle (days inventory + days receivables - days payables) tells you how long your money is tied up before it returns as cash.

This guide covers the formula, the components of working capital, the cash conversion cycle, healthy ratios, ways to improve working capital, and when negative working capital is actually a strategy rather than a problem.

The formula and why it matters

Working capital = Current assets − Current liabilities

Current means within 12 months. Current assets are things you expect to convert to cash in the next year (inventory, customer receivables, cash). Current liabilities are things you expect to pay in the next year (supplier payables, tax due, short-term debt).

Working capital matters because it tells you whether you have enough short-term resources to keep operating. A business with £200,000 of current assets and £100,000 of current liabilities has £100,000 of working capital — a comfortable buffer. A business with £200,000 of current assets and £250,000 of current liabilities has negative £50,000 working capital — a warning sign that obligations are coming due faster than cash is coming in.

Components of working capital

The five main components:

Inventory (stock)

Raw materials, work in progress, and finished goods. Inventory ties up cash from purchase until sale plus the customer payment cycle. High inventory levels protect against stockouts but lock up cash.

Trade receivables (debtors)

Money customers owe you for goods or services already delivered. Receivables are your largest working-capital absorption for most service and B2B businesses. The faster customers pay, the less working capital you need.

Trade payables (creditors)

Money you owe suppliers for goods or services already received. Payables are essentially free finance from suppliers. The longer you take to pay (within agreed terms), the less working capital you need.

Cash

Bank balances and short-term liquid investments. Cash is part of current assets but is also the buffer that absorbs unexpected timing mismatches.

Short-term loans

Overdrafts, invoice finance drawdowns, and any debt due within 12 months. These count as current liabilities and reduce working capital.

The working capital cycle

Three operational metrics measure how long working capital is tied up:

Days inventory outstanding (DIO)

How many days of cost-of-sales the inventory represents.

DIO = (Inventory ÷ Cost of sales) × 365

A retail business holding £100,000 of inventory against £1 million annual cost of sales has DIO of 36.5 days — about five weeks of stock.

Days sales outstanding (DSO)

How many days of revenue the receivables represent.

DSO = (Receivables ÷ Revenue) × 365

A B2B business with £200,000 of receivables on £1 million annual revenue has DSO of 73 days — customers are taking over two months on average to pay.

Days payable outstanding (DPO)

How many days of cost-of-sales the payables represent.

DPO = (Payables ÷ Cost of sales) × 365

A business with £100,000 of payables on £1 million cost of sales has DPO of 36.5 days — paying suppliers in about five weeks on average.

Cash conversion cycle (CCC)

The cumulative effect of all three:

CCC = DIO + DSO − DPO

For our example business: 36.5 + 73 − 36.5 = 73 days. Cash is tied up for 73 days from the moment you commit to inventory or work in progress until you receive payment from the customer.

A short CCC means cash recycles fast and you need less working capital to fund the business. A long CCC means you need substantial working capital. Service businesses with no inventory and quick customer payment can have CCC near zero or even negative; manufacturing businesses with long lead times and slow B2B payment can have CCC of 100+ days.

For more on how working capital sits within the broader balance sheet, see how to read a balance sheet UK.

Healthy ratios

Two key working-capital ratios:

Current ratio

Current assets ÷ current liabilities. Measures liquidity.

A current ratio of 1.5 to 2.0 is generally considered healthy for SMEs. Below 1.0 means current liabilities exceed current assets — short-term solvency strain. Above 3.0 may indicate inefficient use of working capital (too much cash sitting idle, too much inventory, slow customer collection).

Quick ratio (acid test)

(Current assets − inventory) ÷ current liabilities. Stricter than current ratio because it excludes inventory.

A quick ratio of 1.0 or above is generally healthy. Below 1.0 means you would struggle to meet current liabilities if inventory could not be quickly sold.

Industry context matters. Retail businesses can run lower current and quick ratios because they have predictable customer cash flow. Project-based businesses often need higher ratios because their cash flow is lumpier.

Improving working capital

Five practical tactics:

Faster customer collection

Reducing DSO is the highest-impact lever for most businesses. Tactics:

  • Issue invoices on the day work is delivered
  • Tighten payment terms in contracts
  • Set automatic payment reminders (most accounting software does this)
  • Offer 1–2% early payment discount
  • Charge interest on late payments where appropriate

Inventory tightening

Reducing DIO releases cash. Tactics:

  • Just-in-time ordering for predictable demand
  • ABC analysis (focus stock control on high-value items)
  • Sell off slow-moving stock at a discount
  • Renegotiate vendor lead times to reduce safety stock

Negotiated supplier terms

Increasing DPO funds your working capital from suppliers. Tactics:

  • Negotiate longer payment terms (45 or 60 days from 30)
  • Use supplier-credit programmes
  • Pay early only where the discount exceeds your cost of capital

Invoice finance

Convert receivables to cash within 24 hours. Effective annualised cost of 5.5–8.25% on drawn balances for established businesses (2026 industry data). Reasonable when you cannot reduce DSO through customer-side tactics alone.

Right-size the credit line

A revolving credit facility or business overdraft sized to handle peak working-capital need provides resilience without excess borrowing in calm periods.

Negative working capital — when it’s a strategy

Persistently negative working capital is usually a warning sign, but in three business models it can be the deliberate operating norm:

Subscription businesses

Customers pay annually upfront. The business operates on cash collected before services are delivered. Working capital is structurally negative because deferred revenue dwarfs receivables. Software-as-a-service, magazine, and gym businesses commonly run this way.

Supermarkets and high-velocity retail

Customers pay cash at point of sale; suppliers are paid weeks later on credit terms. The result is negative working capital — cash from customers arrives before suppliers are paid. Tesco, Sainsbury’s, and equivalents operate this way structurally.

Construction and project businesses with stage payments

Customers pay milestones in advance, and suppliers are paid on standard credit. Working capital can flip negative depending on the project stage.

For most owner-managed SMEs, none of these models apply, and persistent negative working capital should be addressed.

Key takeaways

  • Working capital = current assets − current liabilities
  • Cash conversion cycle = DIO + DSO − DPO
  • Healthy current ratio is 1.5–2.0; healthy quick ratio is 1.0+
  • Reducing DSO (faster customer collection) is usually the highest-impact lever
  • Increasing DPO (longer supplier terms) funds working capital from suppliers
  • Negative working capital is a strategy in subscription, retail, and stage-paid construction; usually a warning otherwise

Frequently asked questions

What is working capital? Current assets minus current liabilities. It is the short-term financial cushion that funds day-to-day operations between paying suppliers and being paid by customers.

What is a healthy current ratio? Generally 1.5 to 2.0 for UK SMEs. Below 1.0 indicates short-term liquidity strain; above 3.0 may indicate inefficient use of working capital.

What is the cash conversion cycle? Days inventory outstanding plus days sales outstanding minus days payable outstanding. The cumulative time cash is tied up from initial inventory commitment until customer payment lands.

Is negative working capital always bad? No. Subscription businesses, supermarkets, and construction businesses with stage payments can run structurally negative working capital as a deliberate operating model. For most owner-managed SMEs, persistent negative working capital is a warning sign.

How do I improve working capital fast? Tighten customer payment terms and chase aggressively (reduce DSO), negotiate longer supplier terms (increase DPO), reduce inventory (reduce DIO), and use invoice finance for unpaid receivables. Faster customer collection is usually the highest-impact lever.

Useful resources

Financial Reporting Council — FRS 102 https://www.frc.org.uk/

Bank of England — Business finance and credit https://www.bankofengland.co.uk/

GOV.UK — Late payment legislation https://www.gov.uk/late-commercial-payments-interest-debt-recovery