Days sales outstanding is the average time, expressed in days, between a sale entering receivables and the cash for it arriving, computed by dividing a receivables balance by sales for a period and multiplying by the days in that period. It is a management measure derived from two figures already reported on the financial statements rather than a line item presented on them. A lower count means the same volume of billed work is tying up less cash in receivables.
The Days Sales Outstanding Formula
The formula has three inputs, and each one is a choice before it is a number.
DSO = receivables / sales x days in the period
average receivables = (opening receivables + closing receivables) / 2Receivables means the trade balance owed by customers for work already billed, and sales means the revenue earned over the same period that balance is measured against. Two of the three inputs are shared with the ratio this count converts: which balances belong on top, why sales made on credit are the truer denominator than total revenue, and why no filed statement lets an outside reader tell the two apart are all argued at accounts receivable turnover ratio. Days in the period is the input this measure adds on top of that ratio.
The Conventions Nobody States
The multiplier is the days in the period actually being measured: the days in the calendar year for an annual figure, the days in that quarter for a quarterly one, or the shorter banker’s year where a lender or a contract works on one. That shorter year is the 360-day year of 12 30-day months, the form federal regulation uses when it fixes the convention for computing dividend payments (12 CFR 209.1). A wrong day count is silent. The answer still comes out in days, still looks like a collection period, and nothing in the arithmetic objects, so a spreadsheet built for annual figures keeps working when quarterly figures are pasted into it.
The numerator carries a choice of its own, between the closing balance and the average of the opening and closing balances. On a firm whose billing is concentrated rather than even the two pull apart hard, because a closing balance struck days after a large billing run is full of invoices that have had almost no time to be paid. Either way it is a convention rather than a rule, and the choice is set out in cash conversion cycle.
No Rule Settles Any of Them
A ratio built only out of figures already calculated under GAAP falls outside the definition of a non-GAAP financial measure, which excludes operating and other statistical measures, and ratios or statistical measures calculated using exclusively financial measures calculated in accordance with GAAP or operating measures that are not themselves non-GAAP measures (17 CFR 229.10(e)(4)). The reconciliation and disclosure machinery built for non-GAAP measures never reaches this count, and no accounting standard prescribes it either.
What fills the gap is expectation. Where a company-defined metric appears in the management discussion and analysis section of a filing, the SEC would generally expect, based on the facts and circumstances, a clear definition of the metric and how it is calculated to accompany it (SEC, Release No. 33-10751), and what else that guidance asks for is set out in book-to-bill. A private firm is bound by none of that and needs the same habit anyway, because a count quoted without its convention cannot be checked by whoever receives it.
A Worked Example
Say a firm’s books for the year carry the figures below.
Total fees for the year 2,920,000
Fees collected at the point of service 320,000
Receivables, opening 355,000
Receivables, closing 425,000
average receivables (355,000 + 425,000) / 2 = 390,000
net credit sales 2,920,000 - 320,000 = 2,600,000
average balance, total revenue, 365 390,000 / 2,920,000 x 365 = 48.75 days
closing balance, total revenue, 365 425,000 / 2,920,000 x 365 = 53.13 days
average balance, credit sales, 365 390,000 / 2,600,000 x 365 = 54.75 days
average balance, total revenue, 360 390,000 / 2,920,000 x 360 = 48.08 daysOne set of books, four answers, each of them defensible under a stated convention. A firm that quotes any of them without naming the method has published a figure nobody receiving it can reproduce.
How the Count Reads in a CPA Firm’s Own Book
A firm that sells hours has nothing on a shelf between the work and the invoice, so collection speed on billed work carries most of the measure, which is why the cash conversion cycle collapses to this term less days payable outstanding for a practice and why the inventory measure it pairs with there, days inventory outstanding, has nothing to measure.
The count also starts later than the work does. The clock in this formula starts at the receivable, so every day between the work being performed and the right to payment becoming unconditional is invisible to it. A firm with a comfortable count and a slow billing cycle can be holding its cash just as long as a firm with a poor count, and the gap only shows when the unbilled balance is read next to the receivable. Which of the two an amount belongs in turns on whether the right to payment is unconditional, a boundary set out in accounts receivable and work in progress.
What Days Sales Outstanding Is Not
The Accounts Receivable Turnover Ratio
It is the same relationship counted in times rather than days, so either can be derived from the other, and two figures taken off the same statements will not reconcile exactly when one is built on an average balance and the other on a closing balance. That pairing, and a federal computation that writes a collection period down in regulation, sit in accounts receivable turnover ratio.
The Aging Report
This count is one average across the whole book, and an aging report is the distribution underneath it. A comfortable average can sit on top of a ledger where most invoices clear inside terms while a handful have been outstanding for months, and the average moves only once that tail grows heavy enough to drag it, which is well after the aging shows the same accounts. Reading one is covered in the accounts receivable aging report.
The Allowance for Doubtful Accounts
Slow and uncollectible are different findings. The allowance for doubtful accounts estimates what will never be collected, it is not built from this count, and what a move in the count should actually route to is worked through in accounts receivable best practices.
Common Questions
There is no universal figure, because the count only means anything against the credit terms the business actually grants. A count sitting well above those terms says invoices are being paid late on average. A count sitting below them has two readings worth separating, since customers may genuinely be paying early, or part of the denominator may never have gone out on credit at all.
Where a federal program does fix a level, it fixes it for that program alone. HUD’s hospital mortgage insurance rules set a ceiling on days in accounts receivable, as one of the conditions before surplus cash exists to distribute (24 CFR 242.1). The ceiling itself, and what it is measured against, sit with accounts receivable turnover ratio.
Use the quarter’s own receivables, the quarter’s own billings and the quarter’s own day count, which is not the same in every quarter.
receivables at quarter end 210,000
fees billed during the quarter 700,000
days in that quarter 91
DSO 210,000 / 700,000 x 91 = 27.3 days
the same figures with a full year's day count by mistake
DSO 210,000 / 700,000 x 365 = 109.5 daysMixing the scales is the error worth guarding against. A quarter’s sales in the denominator with a year’s days on top produces a figure roughly four times too large, and it is a common way a quarterly number gets quoted as though it were annual.
The arithmetic is one division and one multiplication, so a spreadsheet adds nothing to it. What a spreadsheet should add is the convention. Give the opening balance, the closing balance, the sales figure and the day count their own labelled cells and have the formula reference those cells, so the version in use is visible on the sheet instead of hard-coded inside it. A figure copied out of a sheet without those labels cannot be checked by whoever receives it.
The count falls when the receivables balance shrinks, and it falls just as readily when billings grow while the balance holds still, which is not a collections improvement at all.
390,000 / 2,920,000 x 365 = 48.75 days
390,000 / 3,650,000 x 365 = 39.00 daysSame balance, higher billings, and nobody collected a day faster. Only a movement that comes through the numerator is a collection gain, and deciding which one to chase after the count moves is worked through in accounts receivable best practices.
Accountably places trained offshore accountants inside US CPA and EA firms, and a firm can put a real block of its own billing and collections work through a trial task before anything client facing depends on it.
