How to reduce debtor days and protect working capital

If you want to improve your working capital position in the next 60 days, the single most effective lever is your debtor days — the average time it takes your customers to pay you. Every day you take off that number releases cash that was previously tied up in invoices.

This is a practical playbook for reducing UK SME debtor days by 7-14 days — typically worth £15k-£60k of freed-up cash for a business turning over £500k-£2m — without damaging customer relationships.

First, measure where you actually are

Debtor days = (trade receivables ÷ annual revenue) × 365. Pull it from your current accounting software today. Compare it to:

• Your stated terms. If your terms are net-30 and your debtor days are 54, your customers are on average paying 24 days late.
• This time last year. Direction matters more than absolute number.
• Sector benchmarks. UK B2B services typically run 40-60 days. Distribution 35-55. Construction 55-80.

Any gap between stated terms and actual days is your opportunity.

Second, fix the invoice itself

Most invoice delays are caused by the invoice, not the customer. Fix these basics before anything else:

• Send the invoice immediately. Not weekly, not monthly. Same day as delivery or service completion. Every day of delay in sending is a day added to payment.
• Correct recipient. Confirmed name and email of the person who actually processes payments. Not the buyer, not the project manager — accounts payable.
• Clear due date on the invoice. Not just 'terms: net-30'. An actual date. 'Payment due by 15 May 2026.'
• Purchase order number prominently shown. If your customer uses PO numbers and yours is missing, the invoice goes to the bottom of the pile.
• Payment methods clearly listed. Bank details, sort code, account number, reference to use. No ambiguity.
• Proof of delivery or timesheet attached. If your invoice needs supporting documentation, include it first time — do not wait to be asked.

These fixes alone often cut 5-7 days off average debtor days within 90 days.

Third, chase early and systematically

Most SMEs chase late. Meaning: after the due date. By then it is too late — the invoice is already embedded in the customer's backlog.

Better pattern:

• Day -3 from due date: polite reminder email. 'Invoice 12345 is due in 3 days, payable by bank transfer to the details below. Please confirm everything is in order.' Non-confrontational, and surfaces any problem before it becomes a payment delay.
• Day +1 overdue: phone call, not email. Every day of email silence is a day of additional delay.
• Day +7 overdue: escalation to a named director on your side, reaching out to the customer's finance director. The relationship has stepped up.
• Day +14 overdue: formal notice, potentially with reference to statutory interest under the Late Payment of Commercial Debts Act.

This looks aggressive in print. In practice, it is the discipline that most established SMEs follow — and the discipline that most younger SMEs are too nervous to use. Customers expect it. Many respect it.

Fourth, offer early-payment incentives selectively

A 2% discount for payment within 10 days (instead of net-30) costs you 2% of the invoice but gains 20 days of cash. Annualised, that is a cost of capital of roughly 36% — which is expensive compared to an overdraft but cheaper than factoring and vastly cheaper than running out of cash.

Use this selectively:

• Offer it to customers who genuinely have cash and would take it — typically larger corporates with treasury functions
• Do not offer it to slow-payers who would pay you in 45 days anyway. They won't speed up for 2% — they'll just take the 2% and still pay late.
• Test it on one or two customers before rolling it out across the board.

Fifth, restructure terms on new business

Existing customers are hard to reset. New customers are not. When onboarding a new customer:

• Ask for a deposit. 10-30% upfront is standard for most sectors. Customers who push back hard on deposits are signalling cashflow problems of their own.
• Milestone billing, not end-loading. For services or longer projects, bill at milestones — not one big invoice at the end.
• Shorter terms. Net-14 is a perfectly reasonable B2B term in 2026. You do not have to default to net-30 just because it's the industry convention.
• Direct debit or card-on-file. For recurring clients, this removes the payment friction entirely.

Sixth, know when to walk away

Some customers are structurally slow. They pay eventually, but they cost you 50-70 days of cashflow drag on every invoice. At a cost of capital of even 8%, a customer paying 40 days late on £10k/month invoices costs you £90-£100 per month in real finance cost.

If a chronic slow-payer is also low-margin, the true profitability of that relationship is usually negative once you factor finance cost.

Track the biggest slow-payers by finance-cost burden. Some of them are worth the cost (big-name reference clients, strategic accounts). Most are not.

Action: annually, rank your top 20 customers by (margin − finance cost of their payment pattern). The ones at the bottom get a difficult conversation or a graceful exit.

Common questions