Your biggest customer may be your slowest payer

By Jason Sibley

A big customer feels like security. The orders come regularly, the name looks good on your client list, and there's a finance department that surely knows what it's doing. The latest payment figures suggest you should look again.

This is general information, not financial, legal or tax advice. Speak to your accountant about your own credit exposure and a solicitor about anything contractual.

What D&B's figures show

Dun & Bradstreet (D&B) sells business credit data and risk analytics. These are its figures and comments, so read them with that in mind.

In a pre-Budget comment published by Business Money on 26 October 2026, John Payne, a senior economist at D&B, set out the latest figures. D&B says the share of payments running more than 30 days late fell to 12.4% over the 12 months to September, down from 14.7% a year earlier.

Who pays slowly is less encouraging. D&B says larger firms pay suppliers much more slowly than smaller businesses. Almost 19% of payments from larger firms are running more than 30 days late, compared with under 12% for SMEs.

D&B also says UK company failures are still almost 30% above pre-pandemic levels, though lower than a year ago.

The figures come from the D&B UK Active Universe Trade Payment Report (12 months to September 2026) and the D&B UK Failures By Industry, Q3 2026 Update (12 October 2026). I've used the Business Money write-up rather than the full reports, so check the reports if you need the detail.

These are averages across the economy. Your biggest customer might pay like clockwork, but you shouldn't assume it does.

Why big customers feel safe and aren't always

This section is my opinion, so weigh it accordingly.

A large customer is less likely to vanish overnight than a start-up. That's reassuring, but staying solvent and paying on time are different things. A customer can stay solvent for decades and still take 60 days to settle an invoice you were counting on in 30. The delay hurts a small supplier's bank balance.

Then there's concentration. If one customer accounts for a big slice of your sales, it's usually an even bigger slice of what you're owed. When their payment slips, wages and your own suppliers feel it first. It's hard to push back when you don't want to upset the account that keeps the lights on.

Some large organisations work to fixed payment runs and strict purchase order rules. If yours does, a missing PO number or a missed cut-off can mean waiting for the next run. Check whether that applies to you.

D&B's advice is to reassess three things:

• who you trade with
• how quickly customers are actually paying
• where your credit exposure is concentrated

It adds that changes in payment behaviour can be an early signal of financial stress. A customer who used to pay in 30 days and now takes 45 is telling you something, even if nobody has said a word.

That advice mostly concerns existing customers. For new ones, our guide to a Companies House check before agreeing 30-day terms covers the check to run before you start.

Find out where your cash is tied up

Start with the aged receivables report, sometimes called aged debtors. It lists every unpaid invoice by customer and how overdue it is. Your accounting software can usually produce it. If it can't, your bookkeeper can.

An AI tool can sort the export and do the sums. Strip out anything you don't need to share, and use a tool your business is comfortable with for customer data. Then paste in something like this:

I run a small UK business. Below is an aged debtors export from my accounts. Today's date is [OWNER: add today's date].

Please:
1. Rank my customers by the total amount they currently owe me, largest first.
2. For each customer, show how many days overdue their oldest unpaid invoice is, and the average days overdue across their unpaid invoices.
3. Show each customer's share of the total owed, as a percentage.
4. Flag any single customer who owes more than a quarter (25%) of the total.
5. Finish with a short plain-English summary of what stands out.

Use only the figures I have pasted. Do not invent invoices, dates, amounts or customers. If a column is missing or unclear, or you have to make an assumption, say so and mark it [OWNER TO CHECK]. Do not give financial advice. Write in British English and show your sums so I can check them.

[Paste the aged debtors export here]

The quarter threshold is my own rule of thumb, not a figure from D&B or anyone else. Pick a number that suits your business. Check a few of its sums against the original report before you rely on it.

A weekly cashflow sheet is a simple way to keep track from there.

Four things to change for your biggest payer

Again, these are my opinions. Run any of them past your accountant first.

• Find out their payment run dates and how their purchase order process works. Work backwards so your invoice arrives before the cut-off with the right PO number.
• Ask for their payment terms in writing. If you assumed 30 days and they work to 60, find out now. Our piece on small suppliers accepting bad payment terms is a useful read here.
• Stage payments on big jobs. A deposit up front and milestone payments as work progresses mean you're not funding the whole project yourself.
• Set a credit limit for them. Choose the most you're willing to be owed at any one time, and agree in advance what happens when you reach it. That might mean a conversation or payment before the next piece of work starts.

If payments are already slipping, read our note on fixing terms with slower-paying customers before Christmas.

Know your rights

Small suppliers don't have to put up with late payment. We've written up the late payment rights you already have, and there's a separate piece on the Commercial Payments Bill and late payment. Read them before you send a firm chaser. If a dispute looks likely, speak to a solicitor before you act.

One last thing

At My AI Apprentice we run AI sessions for small businesses, if you'd like to go through a report like this together. No pressure either way.