Debtor Days In Construction: How To Calculate Them And What They Tell You
In construction, an unpaid invoice is rarely just an invoice. It might be an application awaiting certification, a valuation under query, a final account in dispute, or a retention that isn't due for another year. That makes it harder to know how long customers really take to pay, and easier for a cash flow problem to build up unnoticed. Debtor days is one of the simplest ways to bring that into focus.
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 contract payment terms, 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 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 the contract says. Debtor days is what actually happens. 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
A worked example: a contractor 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 the contracts say 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 Figure In Construction?
Construction is usually quoted higher than most sectors because of longer project cycles and staged payments. Published benchmarks vary widely depending on the source, from around the 50s to as high as 90 days, so a generic number is less useful than a comparison with your own contract terms. If your terms are 30 days and your figure is 60, that gap is the thing to investigate, whatever the sector average says.
Retentions, Disputes And Applications
Three things are particular to construction and can distort the figure:
Retentions. These are held back by design until the end of a defects period, which can be 12 months or more. If they're included in trade debtors, they can make debtor days look worse than customers' actual payment behaviour. Many businesses track retentions separately so the main figure reflects day-to-day payment performance.
Disputed applications. A query on an application can leave a sum sitting in debtors for weeks. It helps to flag disputed amounts separately from undisputed ones, so you can see which delays are genuine disputes and which are simply slow payment.
Long payment chains. A delay further up the chain can show up in your numbers a few weeks later, so a rising figure isn't always a problem with your own customer.
What Debtor Days Can't Tell You
It's a useful measure, but it has limits. It looks backwards, so by the time the figure rises, the late payment has already happened. Averages can also hide outliers, with one large overdue account distorting the number. And it doesn't show who is 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 within a range you'd normally accept, is a signal that something has changed in how customers are paying. Pair it with a customer-level view to see 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, including retentions that have fallen due.
Check a customer's credit position before taking on more work, particularly if their payment behaviour has changed.
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 or main contractors have gone quiet, specialist construction debt recovery can help you recover what you're owed.
This article provides general information only.
FAQs
What are debtor days in construction? The average number of days it takes your customers to pay. In construction it's usually higher than in many sectors because of staged payments, long projects and retentions.
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 typical debtor days figure for a construction business? Published figures vary widely by source, from around 50 to 90 days. The most useful comparison is with your own contract payment terms.
Should retentions be included in debtor days? Many businesses track them separately, because retentions are held back by design and can make the main figure look worse than customers' actual payment behaviour.
How can I reduce my debtor days? Chase invoices promptly, check customers' credit before taking on more work, flag disputed sums separately, and escalate stubborn accounts early.
