Days payable outstanding measures how long, on average, you take to pay suppliers. It's one of the three working capital measures, alongside days sales outstanding and days inventory outstanding.
The formula is simple. The interpretation is where it gets interesting, because the same rising number can mean you're managing cash well or that your process has fallen over, and the figure alone won't tell you which.
The formula
DPO = (Average accounts payable ÷ Cost of goods sold) × Number of days in the period
For a full year with COGS of £1.2m and average payables of £150,000:
(150,000 ÷ 1,200,000) × 365 = 45.6 days
For a quarter, use that quarter's COGS and 91 days. Don't mix an annual COGS with a quarterly payables figure — a surprisingly common error that produces a number four times too large.
Average accounts payable is opening plus closing balance, divided by two. Using just the closing balance is quicker and noisier, particularly if your year end falls just after a payment run.
The inputs people get wrong
COGS versus total purchases. Textbooks say COGS. But DPO is measuring how fast you pay suppliers, and your payables include everything you buy on credit — not just cost of sales. For a service business with little or no COGS, the textbook formula produces a meaningless number or divides by nothing.
The practical fix: use total credit purchases instead. Less comparable to published benchmarks, more meaningful for your own business. Whichever you choose, use it consistently — the trend matters more than the absolute figure.
Payables that aren't trade. Accruals, VAT owed, PAYE, deferred income. These sit near payables and aren't supplier invoices. Include them and your DPO inflates for reasons that have nothing to do with suppliers.
Seasonality. A business with a Q4 peak has a very different payables balance in December than in June. Annual averages hide it; if that's you, calculate quarterly.
What a "good" DPO looks like
The honest answer is that it depends on your terms, and there's no universal target.
The useful comparison isn't against an industry benchmark. It's against your own agreed terms. If your suppliers are on 30 days and your DPO is 45, you're paying late — whatever the benchmark says. If they're on 60 and your DPO is 45, you're paying early and giving up working capital for nothing.
So the first step is knowing your weighted average agreed terms. Then DPO tells you something:
| DPO vs your terms | What it means |
|---|---|
| Well below | Paying early. Free financing given away, unless you're taking early settlement discounts |
| At or just below | Working as intended |
| Somewhat above | Either deliberate stretching or a process running late |
| Well above | Late payment. Relationships and credit terms at risk |
The interpretation problem
A rising DPO has two completely different explanations.
Deliberate: you've renegotiated terms or you're paying closer to the due date on purpose. This is genuine working capital improvement.
Accidental: invoices are taking longer to get through approval, so they're paid late rather than late by design. Same number, opposite meaning — and the second is a process failure that happens to look like a treasury success.
These are indistinguishable in the DPO figure alone, which is why it's a poor standalone metric. To tell them apart, look at cycle time: how long from invoice arriving to approved and ready to pay. An aged creditors report split by due date rather than invoice date is the quickest way to see it.
If cycle time is short and DPO is high, you're in control. If cycle time is also long, you're not managing cash — you're behind, and the DPO improvement is an accident you'll pay for in supplier goodwill.
Improving it, honestly
Renegotiate terms. The only method with no downside. Worth asking, particularly with suppliers where your volume has grown since terms were set.
Pay on the due date rather than early. If invoices are paid on arrival because that's the habit, moving to scheduled runs on terms is free working capital.
Shorten cycle time, then choose when to pay. The important one. Approving quickly doesn't mean paying quickly — it means the payment date becomes a decision instead of a consequence.
Consolidate suppliers to build the volume that justifies better terms.
And one worth naming as a bad idea: stretching payments beyond agreed terms without telling anyone. It improves DPO and costs you credit terms, priority when supply is tight, and goodwill you'll want later. It's borrowing from suppliers at a rate you can't see on any statement.
The discount arithmetic
Early settlement discounts complicate DPO deliberately, and the maths usually favours taking them.
A common form is 2/10 net 30 — 2% off if you pay within 10 days, otherwise due at 30. You give up 20 days of cash to save 2%, which annualises to roughly 36%. Unless your cost of capital is extraordinary, take it.
Which means a lower DPO can be the better outcome. Any target that treats "higher is better" as a rule will talk you out of a discount worth far more than the financing.
Where it fits
DPO is most useful alongside DSO and DIO, which together give the cash conversion cycle — how long cash is tied up between paying suppliers and collecting from customers.
On its own, DPO is a number that can be improved by doing something sensible or by doing something harmful, and the figure won't distinguish them. Track it with cycle time beside it and it becomes genuinely useful.
Cribble records invoices on arrival and routes them through approval as a visible queue, which is what makes cycle time short enough for the payment date to be a decision rather than an accident.