How to reduce your debtor days: a practical guide for UK SMEs

There is a number that every business owner should know, and most do not. It is called your debtor days figure — and it tells you, with quiet precision, how long your customers are actually taking to pay you.

For many growing businesses, that figure is higher than it should be. Research published by Aldermore found that over 73 per cent of UK SMEs have some form of outstanding late payment from customers, with businesses waiting an average of 34 days beyond agreed terms before an overdue invoice is settled. Nine hours of staff time, every month, spent chasing money that was already owed. Cash that belongs to your business, sitting in someone else's account.

Understanding your debtor days — and knowing how to bring them down — is one of the most impactful financial improvements you can make without spending a pound on marketing, new technology, or additional headcount.

What are debtor days, and how do you calculate them?

Debtor days — sometimes called days sales outstanding, or DSO — is a measure of how long it takes your business to collect payment after an invoice has been issued. The calculation is straightforward:

• Debtor days = (Trade debtors ÷ Annual credit sales) × 365

So if your business has £30,000 outstanding in unpaid invoices, and your annual credit sales are £200,000, your debtor days figure is 54.75 — meaning it takes, on average, nearly 55 days from the point of invoicing to receive payment. If you offer 30-day payment terms, that figure tells you customers are taking almost four weeks longer than agreed. That gap is where cash flow problems begin.

Why high debtor days matter more than many business owners realise

Late payments are rarely experienced as a single crisis. They accumulate gradually, each unpaid invoice quietly extending the time between completing work and being paid for it. A business with consistently high debtor days finds itself in a permanent state of underwriting its own customers' cash flow — completing work, absorbing the costs, and then waiting, sometimes for months, to receive money it has already earned.

Analysis of over two million invoices by accounting software company FreeAgent found that just over half — 54 per cent — were paid on time. That means for every invoice raised, there is almost a one-in-two chance it will arrive late. Multiplied across a sales ledger of any meaningful size, the cumulative effect on cash flow is substantial.

The good news is that debtor days is one of the most responsive financial metrics available to a business owner. With the right approach, most businesses can reduce their figure meaningfully within three to six months.

Five practical steps to reduce your debtor days

1. Invoice immediately — not eventually

The most common reason for delayed payment is delayed invoicing. Many business owners allow invoicing to drift — completing work, moving on to the next project, and circling back to raise the invoice days or even weeks later. Every day between completion and invoicing is a day added to your debtor days before your customer has even received the bill. Build the discipline of invoicing on the day the work is completed, or at a fixed point in your billing cycle.

2. State your payment terms clearly — every time

Payment terms should be visible on every invoice, in plain English. State the due date explicitly — not 'net 30' but 'payment due by [date]' — and include your bank details without requiring the customer to request them separately. Clear, unambiguous terms reduce the scope for confusion, delay, or the use of administrative queries as a reason to postpone payment.

3. Follow up at day 14 — not day 60

Most businesses follow up on overdue invoices far too late. A brief, professional, friendly follow-up at day 14 — before the invoice is overdue on 30-day terms — is not chasing. It is confirming receipt, checking that the invoice is approved, and keeping a line of communication open. Customers who know their supplier pays attention to invoicing tend to pay more promptly than those who believe an invoice can be left until it becomes pressing.

The tone of this contact matters enormously. A warm, professional reminder reinforces the relationship rather than straining it. This is, in fact, one of the primary reasons many business owners benefit from having credit control managed by a third party — the follow-up is consistent, professional, and entirely separate from the trading relationship.

4. Resolve disputes quickly and completely

Disputed invoices are a significant driver of extended debtor days, and many disputes could be resolved faster with earlier attention. Keep a clear record of all invoice queries, the date they were raised, the response provided, and the agreed resolution. Under the UK government's 2025 reforms, customers will be required to raise invoice disputes within 30 days of receipt — businesses that respond promptly to queries will be in the strongest possible position.

5. Have a clear escalation process — and follow it consistently

When a customer does not pay within agreed terms despite professional reminders, the response should follow a clear, predetermined sequence. A structured escalation process, applied consistently, demonstrates that your business takes its invoicing seriously. This process might include a formal overdue letter at day 35, a direct telephone conversation at day 45, and a written notice of statutory interest at day 60. The specific steps matter less than the consistency with which they are applied.

The honest case for outside support

Many business owners manage their credit control themselves — and many do so effectively. But honest reflection on the numbers suggests that a significant proportion do not. Not because they lack the ability or the intention, but because chasing overdue invoices competes, every day, with the demands of running the business itself.

An outsourced credit control service takes the follow-up process entirely off your plate. Invoices are monitored consistently, reminders are sent at the right intervals in the right tone, and escalation happens on schedule — without any of the social awkwardness that can make asking a valued customer for payment feel uncomfortable.

The cost of professional credit control is, for most small businesses, a fraction of the value of the time and cash flow it recovers. And unlike recruiting an in-house credit controller — where salaries typically range from £20,000 to £35,000 per annum before employment costs — outsourcing gives you access to experienced expertise on a simple monthly retainer, scaled to your needs.

In summary

Reducing your debtor days is not a complex undertaking — but it is a consistent one. It requires prompt invoicing, clear terms, proactive follow-up, fast resolution of queries, and a structured escalation process applied reliably each month. Businesses that build these habits — or work with someone who applies them on their behalf — tend to see their debtor days figure fall meaningfully within a quarter, and their cash flow improve accordingly.

The formula is simple. The discipline is the work. And for many business owners, the best investment they make in that discipline is deciding they do not have to carry it alone.

If you would like to understand how your debtor days compare with what is achievable, or to explore how outsourced credit control could help your business get paid faster, please contact that credit control today.