Debtor Days: The UK Term for DSO (and What It Actually Tells You)

What Are Debtor Days?

Debtor days measures how long, on average, it takes your customers to pay their invoices. It is the UK and Commonwealth equivalent of Days Sales Outstanding (DSO), calculated the same way, used for the same purpose: tracking how fast receivables convert to cash.

If your team already runs DSO reporting, debtor days is the same number with a different name. For companies trading internationally, or for UK-based teams benchmarking against peers, understanding the terminology matters.

The Debtor Days Formula

Debtor Days = (Trade Debtors / Revenue) × 365

For a shorter period:

Debtor Days = (Trade Debtors / Revenue) × Number of Days in Period

Where Trade Debtors = total outstanding accounts receivable at the end of the period.

Example: A company with £500,000 in outstanding receivables and £6M in annual revenue:

Debtor Days = (500,000 / 6,000,000) × 365 = 30.4 days

How Debtor Days Differs From DSO

It does not, really. The terms are interchangeable. DSO is standard in the United States. Debtor days is standard in the UK, Australia, and most of the Commonwealth. Both use the same formula and both appear on the same financial analysis reports.

The only meaningful difference: UK accounting standards refer to "trade debtors" where US standards say "accounts receivable." Same line item, different label.

If you are comparing your metrics against international benchmarks, confirm which term the source uses before drawing conclusions. A UK report citing "30 debtor days" and a US report citing "30 DSO" are measuring the same thing.

What Is a Good Debtor Days Number?

The benchmark varies significantly by industry. Manufacturing companies often run 45 to 60 debtor days. Software and SaaS companies typically sit at 30 to 45 days. Construction frequently runs 60 to 90 days because of longer project payment cycles.

For a detailed breakdown by sector, see the DSO by industry benchmarks post, which covers over 20 industries with 2024 to 2025 data.

The more useful question is not whether your debtor days figure is "good." It is whether it is getting better or worse, and why.

The Problem With Using Debtor Days as Your Primary Metric

Debtor days is a trailing metric. It tells you what already happened: the average payment behavior across your entire customer base, expressed as a single number. By the time debtor days deteriorates, the damage is usually absorbed.

Here is what debtor days will not tell you:

Which customers are the problem. An aggregate number masks the difference between a large customer running 75 days and the rest of the book running 28. Both blend into one figure. The real risk is concentrated in the outliers.

Why a customer slowed down. A jump in debtor days could mean cash flow problems, a back-office dispute, an invoice error, or a customer deliberately stretching terms because their own business deteriorated. The metric gives you no signal about cause.

Whether a slowdown is a leading indicator of default. Customers frequently slow payment before they stop paying entirely. But by the time debtor days moves, you have often missed the window to intervene.

Credit teams that run their program from a debtor days dashboard are reviewing the crime scene, not preventing the crime. The number is worth tracking for board reporting and investor conversations. It should not be the primary signal your team acts on.

For a credit program that catches deteriorating accounts before they show up in aggregate metrics, see how B2B credit risk monitoring works at the account level.

How to Improve Debtor Days

If your debtor days number is trending in the wrong direction, there are a few levers worth pulling.

Tighten your invoice process. Late invoices create late payments. Sending an invoice two weeks after delivery and then counting debtor days from the delivery date flatters your number. Send invoices immediately. Make sure invoice details are accurate. A disputed invoice sits in debtor days without generating cash.

Shorten payment terms selectively. Net 60 customers pay in 60 days. If your credit policy allows variable terms, run the analysis: which customers have clean payment history and could reasonably move to Net 30? A 15-day reduction across 20% of your book moves debtor days materially.

Start collections earlier. Most B2B teams run the first chaser at 7 to 14 days overdue. Moving that to day 1 overdue, even just an automated reminder, reduces the long tail of slow payers without damaging relationships. For escalation paths after that, see the dunning process guide.

Monitor at the account level, not the aggregate. Debtor days as a company average is a reporting metric. For operations, you need to know which accounts are running long today, not what the average was last quarter. Account-level AR monitoring catches concentration risk and deteriorating customers before they pull the overall number down.

For a full set of tactics, the how to reduce DSO guide covers the same levers in more detail.

Debtor Days vs. Creditor Days

Creditor days, known in the US as Days Payable Outstanding, measures the flip side: how long your company takes to pay its own suppliers.

Creditor Days = (Trade Creditors / Cost of Goods Sold) × 365

A company with high debtor days and low creditor days is financing its customers with its own operating cash. This is a common squeeze point for small and mid-market businesses.

Watch the spread between debtor days and creditor days. When debtor days exceeds creditor days by more than 20 to 30 days, you are typically running a structural working capital deficit that will need to be funded by credit lines or equity. The Days Payable Outstanding guide covers the creditor side of this equation.

Debtor Days in Financial Analysis

Analysts reviewing a company's financial health look at debtor days as part of a working capital analysis alongside creditor days and inventory days. Together, these three metrics make up the cash conversion cycle.

High debtor days relative to peers suggests one of three things: a credit policy that is too lenient, a collections process that is too slow, or a customer base under financial stress. All three have different solutions.

For a company raising debt financing or preparing for an acquisition, debtor days over 60 will draw scrutiny. A buyer or lender wants to understand whether the receivables balance is collectible. A high debtor days figure suggests a meaningful portion might not be.

The Cash Conversion Cycle guide covers how debtor days fits into the broader working capital analysis.

Frequently Asked Questions

What is the formula for debtor days?
Debtor Days = (Trade Debtors / Revenue) × 365. For shorter periods, replace 365 with the number of days in the period.

What is the difference between debtor days and DSO?
Nothing substantive. Debtor days is the UK and Commonwealth term. DSO (Days Sales Outstanding) is the US term. Both measure average receivables collection time using the same formula.

What is a good debtor days ratio?
It depends on your industry and customer mix. Manufacturing typically runs 45 to 60 days. SaaS runs 30 to 45 days. Construction runs 60 to 90 days. The benchmark matters less than the trend: is your number improving or deteriorating?

How do I reduce debtor days?
The fastest levers: send invoices immediately after delivery, start collections outreach on day 1 overdue, tighten terms for customers with clean payment history, and identify the 5 to 10 accounts driving the most receivables concentration.

Why is debtor days considered a trailing metric?
Because it reflects what already happened. A deteriorating debtor days number means your customers already slowed their payments. You are measuring the aftermath. Account-level monitoring on financial signals catches problems earlier, before they show up in aggregate metrics.