Why do invoices go unpaid?

Late payments cost UK small businesses billions every year. Common reasons invoices go unpaid include the client simply forgetting, cash flow problems on their end, disputes over the work, or administrative issues in their accounts payable process. Understanding the cause helps you choose the right approach.

Step 1: Send a friendly reminder

On or just after the due date, send a polite email reminder. Keep the tone friendly — assume it is an oversight rather than deliberate non-payment. Include the invoice number, amount and due date. Attach a copy of the original invoice.

Example subject line: Friendly reminder — Invoice INV-2025-041 due [date]

Step 2: Follow up by phone

If there is no response to your email within 3–5 working days, call the client directly. Speaking to someone personally is far more effective than email alone. Be professional and matter-of-fact — simply confirm they received the invoice and ask when payment will be made.

Step 3: Send a formal overdue notice

If the invoice is more than 14 days overdue, send a formal written notice stating the amount owed, the original due date and that you intend to apply statutory interest under the Late Payment of Commercial Debts (Interest) Act 1998.

UK law entitles you to charge:

  • Statutory interest at 8% above the Bank of England base rate
  • Fixed debt recovery costs (£40 for debts under £1,000, £70 for £1,000–£9,999, £100 for £10,000+)

Step 4: Consider a payment plan

If the client has genuine cash flow problems, offering a structured payment plan can help you recover the money while preserving the relationship. Get any agreement in writing.

Step 5: Escalate if necessary

If all else fails, your options include:

  • Small Claims Court — for debts up to £10,000, this is a relatively straightforward process
  • Debt collection agency — they take a percentage but handle the process for you
  • Statutory demand — a formal legal notice that can lead to insolvency proceedings for amounts over £750

Prevention is better than cure

The best way to deal with late payments is to prevent them. Always send invoices promptly, set clear payment terms upfront, follow up on the due date automatically, and consider requiring deposits for larger projects.

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