Debtor days for wholesalers: what your number should be, and what each day costs

Debtor days, called DSO or days sales outstanding in the US, is your receivables balance divided by credit sales for the period, times the days in that period. In the UK the textbook version overstates it by about 20%, because the receivables balance carries output VAT and the revenue line does not. Correct that before you set a target.

A wholesaler is more exposed than most, because the cash in an unpaid invoice is mostly not profit. It is money already paid to suppliers for goods that have left the building.

The debtor days formula, and the VAT error inside it

Debtor days = (trade receivables ÷ credit sales for the period) × days in the period. In a UK VAT-registered business the two inputs are measured on different bases, so the raw division is wrong before you start.

Invoice a trade customer £10,000 of standard-rated goods and they owe you £12,000, because VAT Notice 700 requires the tax to be charged and shown on the invoice as part of the total payable. Your sales ledger carries £12,000. Your profit and loss records £10,000, because the £2,000 is output tax owed to HMRC, not income.

Put the ledger balance over the revenue line and the numerator is 20% larger than the basis of the denominator. The answer comes out 20% high, every month, for every VAT-registered UK business using the standard formula.

The second error is worse, because it is invisible. Every version of the formula in circulation asks for "total credit sales", and no line of that name exists in Xero or QuickBooks Online. So people take total income, which includes counter takings and card sales that never enter receivables.

Those two errors run in opposite directions and there is no reason they cancel. Take the worked example below. £1,800,000 of receivables over £10.6m of total income, which carries £600,000 of counter sales, gives 62.0 days. Over £10m of net trade sales, 65.70. The right answer is 54.75.

Days sales outstanding is the same number with a US name

DSO and debtor days are the same calculation. The vocabulary changes with the market, the arithmetic does not.

US and international finance teams say days sales outstanding, or DSO. UK and Australian teams say debtor days, and "AR aging report" is the US name for the aged debtors report.

The VAT problem is UK, Irish and European. There is no US equivalent, because sales tax is not usually invoiced on a B2B wholesale sale carrying a resale certificate. Our guide to the DSO calculation formula covers that version.

Where the two numbers actually live in Xero and QuickBooks

In Xero the debtor days numerator is the total on the Aged Receivables Summary, which is gross of VAT. The denominator is invoiced trade sales from the profit and loss, which is net, and counter sales must come out of it first.

The numerator. In Xero it is the total on the Aged Receivables Summary; in QuickBooks Online, the accounts receivable ageing summary. Both are gross, because that is what the customer owes.

Standard guidance says to average the opening and closing receivables balance, and for a year-on-year ratio that is right: it stops one odd month-end distorting the comparison.

For running a wholesale ledger, take the closing total. Averaging two points twelve months apart flattens the seasonal peak you need to see, and the operating question is what is owed now. Countback handles seasonality properly.

The denominator. Take invoiced trade sales, not total income. If counter or cash sales sit in the same revenue account, split them out: a separate income account or a tracking category fixes the number permanently.

The VAT rate. Do not assume 20%. Divide output VAT charged on sales by net sales for the period, roughly box 1 over box 6 on a UK VAT return. A builders merchant lands near 20%; a food wholesaler selling largely zero-rated grocery lands far below, and over-correcting is as wrong as not correcting.

Work out your corrected debtor days

A UK wholesaler with £1,800,000 on the aged receivables report and £10m of net credit sales shows 65.70 textbook debtor days and 54.75 corrected, a gap of 10.95 days.

The same sum by hand

A wholesaler turning over £10m of credit sales a year, the ONS average for the division, closes the year with £1,800,000 on the aged receivables report at a blended 20% output VAT rate.

• Textbook: 1,800,000 ÷ 10,000,000 × 365 = 0.18 × 365 = 65.70 days
• Strip the VAT: 1,800,000 ÷ 1.20 = £1,500,000 of net receivables
• Corrected: 1,500,000 ÷ 10,000,000 × 365 = 0.15 × 365 = 54.75 days
• Difference: 65.70 − 54.75 = 10.95 days
• Cost of one day: 10,000,000 ÷ 365 = £27,397.26 of sales a day, funded at 9% = £2,465.75 a year
• The gap: 10.95 × 2,465.75 = £27,000 of funding cost that was never real

The correction does not get you paid faster. It stops you targeting a number 11 days pessimistic, and stops a VAT rate change reading as an improvement. A standalone version sits on our days sales outstanding calculator.

What good looks like on a wholesale ledger

No trade body publishes a wholesale-specific debtor days benchmark in the UK, the US, Australia or New Zealand. The rows below separate what somebody else published from what I recommend.

One warning on the target row. On "30 days end of month following" the effective credit period averages 45.5 days and ranges from 31 to 60, set purely by where in the month the customer ordered. A target that does not normalise for that measures order timing, not collections, as the wholesale credit control pillar works through.

Countback, best possible DSO, ADD and CEI

Simple debtor days is the number you report. Countback is the number you manage by, because it does not lie when sales are seasonal.

Take sales of £900k in June, £1,000k in July and £1,100k in August, with receivables of £1,600k at 31 August, £1,300k of it current. All net of VAT.

• Countback. August sales of £1,100k are less than the £1,600k balance, so consume August whole: 31 days. £500k remains, and July sales are £1,000k, so the part month is (500 ÷ 1,000) × 31 = 15.5 days. Countback DSO = 46.5 days.
• Simple, three months. 1,600 ÷ 3,000 × 92 = 49.07 days, overstating by 2.57 days because recent sales are rising. On falling sales the sign flips.
• Best possible DSO. 1,300 ÷ 3,000 × 92 = 39.87 days, what you would post if everyone paid exactly to terms.
• Average days delinquent. 49.07 − 39.87 = 9.20 days, the collections number isolated from your terms.
• Collection effectiveness index. With opening receivables of £1,500k: (1,500 + 3,000 − 1,600) ÷ (1,500 + 3,000 − 1,300) × 100 = 2,900 ÷ 3,200 = 90.6%.

Report simple debtor days to the board, manage on countback, and use average days delinquent to separate collections from sales mix. In a seasonal ledger the simple method is wrong in whichever direction the season runs.

Creditor days is the mirror image: trade payables ÷ purchases × days. It carries the same VAT error, because payables are gross of input VAT while purchases are net.

Run both. Creditor days minus debtor days is your funding gap, and in wholesale that gap is mostly cash already paid to a supplier. Pay in 30, collect in 45, and you fund fifteen days of cost of sales on every account.

Settlement discounts are an expensive way to buy days

A 2% discount for payment in 10 days on 30-day terms costs the seller 37.2% a year, more than three times UK statutory interest.

The arithmetic. Annualised cost = [d ÷ (1 − d)] × [365 ÷ (N − D)], where d is the discount, N the net term and D the discount period. For 2/10 net 30: 0.02 ÷ 0.98 = 0.020408, and 365 ÷ (30 − 10) = 18.25, so 0.020408 × 18.25 = 0.3724, or 37.2% a year.

Then the margin test. At the ONS 13.60% gross margin proxy, that same 2% surrenders 14.7% of gross margin (2 ÷ 13.6) to move cash 20 days.

Since 1 April 2015, VAT must be accounted for on the amount actually paid, so every discount taken needs a credit note or invoice adjustment: an accounting cost on top of the margin.

The unearned discount is worse here than in per-invoice trading. On one monthly payment covering 200 invoices, a 2% deduction taken without qualifying looks like an unexplained residual and is almost never charged back.

What one unpaid invoice actually costs

At the UK wholesale gross margin proxy of 13.60%, one £10,000 write-off needs £73,529 of replacement sales to earn the profit back. A 60% margin service business needs £16,667: 4.4 times less work for the same hole.

The ONS Annual Business Survey, released 26 May 2026, records SIC Division 46 turning over £1,018,705m in 2024 across 101,213 enterprises against purchases of £880,158m: a gross margin proxy of 1 − (880,158 ÷ 1,018,705) = 13.60%.

Treat that as a proxy, not a measured margin, and as the thin end of the range. SIC 46.71 fuels drags it down: 36.9% of divisional turnover at a 6.54% proxy. Strip fuels out and the rest of the division proxies at 17.74%.

• Wholesale, 13.60% proxy. 10,000 ÷ 0.136 = £73,529, or 7.35 further invoices of the same size.
• Service business, 60% margin. 10,000 ÷ 0.60 = £16,667, or 1.7 invoices.
• The ratio. 73,529 ÷ 16,667 = 4.4 times more revenue for the identical write-off.

The reason is what the invoice is made of. At 13.60%, £8,640 of every £10,000 is cash already paid to suppliers for goods now in the customer's warehouse. A cash loss, not a lost opportunity, and it happened at despatch, not at the due date.

So debtor days is a stock and despatch metric with a finance name. Where recovering the goods is still possible, retention of title and deductions covers what your terms must say, and how payment allocation can destroy the claim.

Bring the number down without hiring

Debtor days falls for three reasons: invoices go out sooner, the cadence is consistent, and late payment carries a cost. The first is operations, the rest is automation.

Paidnice runs on Xero or QuickBooks Online and takes the repeatable parts off a person:

• Reminder sequences per customer group, firm for chronic late payers, lighter elsewhere
• Automatic statements including consolidated parent and child, the highest-yield contact on a statement-traded ledger
• Late fees and statutory interest posted onto the invoice, with the UK rate auto-indexed to the Bank of England base rate. What a goods supplier may charge is in charging interest on overdue invoices
• Escalation workflows and a customer payment portal, so the chase and the payment sit in one place

Customers cut their average wait for payment in half, within 30 days. Pricing is from £49 / US$69 a month for 150 invoices, Pro from £74 / US$99, no per-seat fees. Statements run from automated customer statements.

The honest limit, and it matters more in wholesale than anywhere: Paidnice sits on the ledger, not the order book, so it does not block an order at entry. For the comparison, see the best credit control software for wholesalers.

Common questions

The formula is the easy half. The credit control process for wholesalers sets out the order gate, the cadence and the point supply stops.

Written by

Denym Bird

Co-founder & CEO of Paidnice

Denym is a software entrepreneur and writes about accounts receivables management for small business.

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