Are debtor days and DSO the same thing?

Yes. Debtor days, days sales outstanding, receivable days and the debtor collection period are names for one idea: how many days of sales are sitting unpaid. British and New Zealand accountants tend to say debtor days and North American sources DSO. The conventions under the name vary, chiefly closing or average debtors and total or credit sales, so two published figures are comparable only if they were built the same way.

What is a good debtor days figure?

There is no single figure, because the answer depends on the terms a trade customarily gives. A supermarket supplier, a contractor waiting on progress claims and a retailer selling for cash would each show very different numbers in good health. The useful comparisons are with the business's own payment terms and its own history. Days well beyond the stated terms mean customers are paying late; days rising faster than sales mean something has changed.

Should debtor days be calculated with or without GST?

Both sides need to be on the same basis. Sales in the accounts exclude GST or VAT, while the debtors balance usually includes what was invoiced, so dividing one by the other overstates the days. The usual fix is to strip the tax from debtors at the applicable rate. Where a business sells both domestically and abroad, or sells some zero-rated goods, the rate has to be blended, and a lender can ask for the ledger net of tax.

How can a business reduce its debtor days?

Invoice promptly and accurately, since a late or disputed invoice starts the clock late. Agree terms before the sale, chase before the due date as well as after it, and resolve disputes quickly. Some businesses offer a discount for early payment, which has a real cost, or use invoice finance, which brings the cash forward but does not make the customer pay sooner. A lender is more impressed by a falling figure with a cleaner ageing than by one reached through a month-end push.

// WORKED EXAMPLETHE ARITHMETIC A DECISION RESTS ON

Debtor Days: a Worked Example

More sales need more funding. Slower payers need a question.

BY MICHAEL SHANG · SIXTEEN YEARS IN COMMERCIAL BANKING · UPDATED 2026-11-09 · 6 MIN READ

// THE SHORT ANSWER

When a borrower asks to lift its debtor funding, a lender splits the request in two: the part that more sales explain and the part that later payment explains. Debtor days make the split possible by expressing the receivables balance as days of sales: closing trade debtors divided by sales, times the days in the period, with GST or VAT removed so both sides match. The figure alone says little, because terms differ by trade. What a lender reads is how it moved against sales, and which customers moved it.

BASIS Practitioner judgment from sixteen years in commercial banking, set out in How Bankers Think (Highbank Press, 2026). Every borrower on this site is a composite constructed for teaching, not a client. The market is mid-market commercial lending as practised in New Zealand and Australia; where a convention differs elsewhere, the page says so.

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PART OF Credit Analysis for Beginners

// 01 — WHAT THE NUMBER SAYS THAT SALES DO NOT

Every sale on credit is a small loan to a customer until the invoice is paid, and the business funds those loans from its suppliers, its owners or its bank. Revenue says how many loans were written. Debtor days say how long they stay out. A business can need more funding because it is selling more, which is a growth question, or because the same customers are taking longer, which is a question about the customers or about the collection desk.

The figure is also called days sales outstanding, DSO or receivable days. It is one leg of the cash conversion cycle, with stock days added and creditor days taken away.

// 02 — HOW THE FIGURE IS CALCULATED

Debtor days = trade debtors ÷ credit sales × days in period

Debtors ex tax = debtors as shown ÷ (1 + tax rate)

Count-back: take closing debtors, subtract the latest month's

sales and count that month's days; repeat until debtors run out.

Four choices change the answer. Textbooks often average opening and closing debtors, which suits a stable business; a lender watching direction prefers the closing balance or monthly figures, because averaging delays the news. Credit sales are the right denominator where cash sales can be separated. Tax needs matching: sales are reported net, while a debtors ledger usually includes the tax invoiced, at 15% GST in New Zealand, 10% GST in Australia and 20% standard-rate VAT in the UK, with exports commonly carrying none. And annual sales mislead when sales are seasonal or rising fast, which is what the count-back method corrects by comparing debtors with the most recent months.

// 03 — THE EXAMPLE

An automotive paint wholesaler in New Zealand, constructed for this page like every figure in it, sells to independent panel beaters and to three insurer-linked repair chains. Sales rose from US$42.0m to US$49.0m. Debtors on the balance sheet, including 15% GST, rose from US$8.28m to US$12.42m. It asks its lender for US$3.6m more.

Last year This year

Debtors ex GST 8.28 ÷ 1.15 = 7.20 12.42 ÷ 1.15 = 10.80

Debtor days 7.20 ÷ 42.0 × 365 = 62.6 10.80 ÷ 49.0 × 365 = 80.4

Debtors at last year's days: 49.0 × 62.6 ÷ 365 = 8.40

Explained by growth: 8.40 − 7.20 = 1.20

Explained by longer days: 10.80 − 8.40 = 2.40

The request = 3.60

Sales grew by a sixth and debtors by half. Without removing GST the figures would read 72.0 and 92.5 days, overstating the level on both sides. On an average of the two balances the figure is 67.0 days, which hides most of the move. On count-back, with June sales of US$4.6m, May of US$4.4m and April of US$4.0m, the remaining US$1.8m is 45% of April, and the answer is 30 + 31 + 13.5 = 74.5 days, lower because recent months ran above the year's average. Now the ledger, split by customer:

Sales Debtors Days

Independents, last 34.0 5.5 59.0

Independents, this 30.0 4.5 54.8

Three chains, last 8.0 1.7 77.6

Three chains, this 19.0 6.3 121.0

All the growth came from the chains. The independents paid slightly faster but bought less, and the chains' share of the debtors rose from 24% to 58%. The whole-book average rose by 18 days; the chains' own figure rose by 43. Had each group paid at last year's pace, debtors would be US$8.89m, not US$8.40m, so US$0.49m of the US$2.40m is the sales mix moving towards slower payers and US$1.91m is slower payment itself. So the first question is what the chains were promised: agreed long terms are a pricing decision the wholesaler made, while invoices disputed or simply unpaid are a different file. The levels here are the example's, not a market norm.

// 04 — WHAT A LENDER READS BESIDE IT

Debtor days are an average, and an average can hold still while everything under it moves. The aged debtors report gives the distribution: how much is current, how much is 30, 60 or 90 days past due. Customer concentration shows who owes it. A figure that is steady for two years can still describe a ledger that has narrowed to a handful of names.

Debtor days also need reading with the other side of the trade. If creditor days have stretched by the same amount, the business has been passing the delay to its suppliers, and that has a limit a lender wants to see before the suppliers do.

DEFINED IN ONE PARAGRAPH → · AGED DEBTORS → · THE WORKING CAPITAL REQUEST →

// 05 — WHERE IT DECIDES A FILE

The split sizes the request, and the ledger then shows whose request it is. On the whole-book arithmetic US$1.2m follows sales and could be argued on the growth plan, but the growth is the chains' too, so all US$3.6m leads to the same three customers and funding it means taking a view on them. If the facility is invoice finance or tested against a borrowing base, the document may answer for the lender: many agreements exclude invoices beyond a set age and cap the share any one debtor may represent, so the debts that grew most may raise the least funding.

After drawdown, the figure belongs in monthly reporting. A lender tracking it by customer group can see a slowdown before it reaches a covenant, while there is time to ask about terms, disputes and what has been verified.

// SOURCES

The documents the statements on this page rest on. Each was opened and checked when cited.

Inland Revenue (New Zealand), What GST is — GST is 15% and is added to the price of most goods and services, the rate removed from the debtors balance in sections 02 and 03.
GOV.UK, VAT rates — The UK standard rate of VAT is 20%, with a zero rate for some goods, as stated in section 02.

// QUESTIONS PEOPLE ASK

Are debtor days and DSO the same thing?: Yes. Debtor days, days sales outstanding, receivable days and the debtor collection period are names for one idea: how many days of sales are sitting unpaid. British and New Zealand accountants tend to say debtor days and North American sources DSO. The conventions under the name vary, chiefly closing or average debtors and total or credit sales, so two published figures are comparable only if they were built the same way.
What is a good debtor days figure?: There is no single figure, because the answer depends on the terms a trade customarily gives. A supermarket supplier, a contractor waiting on progress claims and a retailer selling for cash would each show very different numbers in good health. The useful comparisons are with the business's own payment terms and its own history. Days well beyond the stated terms mean customers are paying late; days rising faster than sales mean something has changed.
Should debtor days be calculated with or without GST?: Both sides need to be on the same basis. Sales in the accounts exclude GST or VAT, while the debtors balance usually includes what was invoiced, so dividing one by the other overstates the days. The usual fix is to strip the tax from debtors at the applicable rate. Where a business sells both domestically and abroad, or sells some zero-rated goods, the rate has to be blended, and a lender can ask for the ledger net of tax.
How can a business reduce its debtor days?: Invoice promptly and accurately, since a late or disputed invoice starts the clock late. Agree terms before the sale, chase before the due date as well as after it, and resolve disputes quickly. Some businesses offer a discount for early payment, which has a real cost, or use invoice finance, which brings the cash forward but does not make the customer pay sooner. A lender is more impressed by a falling figure with a cleaner ageing than by one reached through a month-end push.

// NEXT TO IT

// ON WHOSE DESK

The seats that read this term in an ordinary week. Each page says what the seat is for, who arrives in it, and the shape of the round it runs.

Credit analystReads a borrower and writes the recommendation a decision-maker will act on.
Credit sanctionerHolds delegated authority and signs — or declines — the lending the front line brings.
Portfolio managerOwns the credit on a book after the money is out — reviews, covenants, ratings and early warning.

THE IN-TRAY · ONE MINUTE

Make the call on one file.

A short file on the ground this page covers. Every option opens with how far it sits from a senior banker’s read.

THE NUMBER · THE LOAN · CAPACITY

A company asks to refinance. Its year in four numbers:

EBITDA: US$6m
Capex + tax: US$2m
Interest: US$1m
Principal due: US$2m

What is its debt service cover, on cash available after capital spending and tax?

5 MORE ON THE LOAN · CAPACITY →WHERE DO YOU READ FROM? THE PLACEMENT →

THE READING ROOMIN ONE PARAGRAPHDebtor days What do debtor days (DSO) tell a lender that revenue growth does not?