What DSO tells you, and what it hides

Days sales outstanding, or DSO, is the number most finance and credit teams use to judge how fast customers pay. It is simple to work out. That is its strength, and its weakness.

How DSO is calculated

Take accounts receivable at the end of a period. Divide it by credit sales for that period. Multiply by the number of days in the period.

Say you close a 90-day quarter with 500,000 in receivables, after 1.5 million in credit sales. 500,000 divided by 1.5 million, times 90, gives a DSO of 30 days.

Why a lower DSO matters

A lower DSO means cash comes in sooner. Cash that arrives sooner pays suppliers, funds hiring and cuts borrowing. That is why DSO shows up in board decks and lender reviews.

But one number can hide a lot.

What one number hides

It hides who is late

A DSO of 30 days can mean every customer pays in about 30 days. It can also mean most customers pay in 10 days and one large account is 90 days late. Those are very different problems. An aging report, which groups open invoices by how overdue they are, shows the difference.

It moves when sales move

The formula divides by sales. So a strong sales month can make DSO look better even when no customer paid any faster. A slow month can make it look worse for the same reason.

It says nothing about why

A late payment might be a customer short on cash. It might also be a disputed invoice, a missing purchase order number, or an invoice sent to the wrong contact. Each one needs a different fix, and the DSO figure cannot tell you which.

Track DSO, but not on its own

Read it next to your aging report, your largest overdue accounts, and the reasons invoices are late. The number tells you something changed. The detail tells you what to do about it.