What Are Debtor Days? How To Calculate Them And What They Tell You
You can know exactly which invoices you've sent and still have no idea how long your customers really take to pay them. Debtor days gives you a single number that answers that question, and it's one of the quickest ways to spot a cash flow problem before it becomes a crisis.
In short: debtor days measures the average number of days it takes your customers to pay you. The standard formula is trade debtors ÷ annual credit sales × 365. If the answer is higher than your payment terms, your customers are paying late on average. It looks backwards at what has already happened, so it's most useful when tracked over time.
What Debtor Days Measure
Debtor days is the UK term for what's often called days sales outstanding (DSO) elsewhere. It's the same calculation, and it shows how long, on average, your cash is tied up in unpaid invoices.
It isn't the same as your payment terms. Payment terms are what you agreed with the customer, such as 30 days. Debtor days is what actually happens in practice. The gap between the two is where late payment shows up.
How To Calculate Debtor Days
The standard formula is:
Debtor days = (trade debtors ÷ annual credit sales) × 365
Trade debtors is the total currently owed to you by customers. Credit sales are sales made on credit terms, so cash sales are left out.
A worked example: a business has £60,000 owed by customers and £480,000 of annual credit sales. £60,000 ÷ £480,000 = 0.125, and × 365 = 45.6 days. If its payment terms are 30 days, customers are taking about 15 days longer than agreed on average.
If you want a faster read on recent trends, you can use a monthly version: (trade debtors ÷ monthly credit sales) × 30. Whichever method you choose, use the same one every time so the figures are comparable.
What's A Good Debtor Days Figure?
It depends on your payment terms and your sector. A figure of 30 to 45 days is commonly cited as healthy for many small businesses, but a better test is to compare it with your own terms. If you sell on 30-day terms, a figure in the 30s is solid. A figure that's much higher means customers are stretching you further than you agreed.
What Debtor Days Can't Tell You
It's a useful measure, but it has limits:
It looks backwards. By the time the figure rises, the late payment has already happened.
Averages hide outliers. One large overdue account can distort the number, and a handful of small late payers can be masked by lots of on-time ones.
It doesn't show who. The figure alone won't tell you which customers are slipping, so use it alongside an aged debtors report.
Using Debtor Days As An Early Warning
The most useful thing you can do with debtor days is track it every month. A rising trend, even while it's within a range you'd consider acceptable, is a signal that something has changed in how customers are paying. Pair the trend with a customer-level view to see exactly where the slippage is coming from.
What To Do When Your Debtor Days Start Rising
A few practical steps are worth taking early:
Review your aged debtors to see which accounts are driving the increase.
Chase promptly and consistently, rather than waiting for an invoice to become seriously overdue.
Check a customer's credit position before extending further credit, particularly if their payment behaviour has changed.
Consider tighter terms for customers who regularly pay late.
Escalate stubborn accounts sooner. The longer an invoice sits, the harder it tends to be to recover.
If your debtor days are climbing because certain customers have gone quiet, specialist commercial debt recovery can help you recover what you're owed.
This article provides general information only.
FAQs
What are debtor days? The average number of days it takes your customers to pay their invoices. It's the UK term for days sales outstanding (DSO).
How do you calculate debtor days? Divide trade debtors by annual credit sales, then multiply by 365. For example, £60,000 ÷ £480,000 × 365 = 45.6 days.
What is a good debtor days figure? It depends on your terms and sector. A figure of 30 to 45 days is commonly cited as healthy for many small businesses, but the best comparison is with your own payment terms.
What's the difference between debtor days and payment terms? Payment terms are what you agreed with the customer. Debtor days is how long customers actually take to pay on average.
How can I reduce my debtor days? Chase invoices promptly, check customers' credit before extending more credit, tighten terms for habitual late payers, and escalate stubborn accounts early.
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