What is days sales outstanding (DSO)?

If you sell on credit terms such as net 30, you are lending your customer money for a while. DSO tells you how long that loan really lasts, compared with what the terms say.

Why DSO matters

A sale is not cash until the customer pays. Between the invoice and the payment, you have already paid for materials, wages and freight. The longer that gap, the more cash you need to keep the business running.

DSO is a quick way to see the gap. If your terms are 30 days and your DSO is 52, customers are paying much later than agreed, or a few large late invoices are pulling the average up.

The DSO formula

DSO = accounts receivable ÷ credit sales × number of days in the period

• Accounts receivable is what customers owe you at the end of the period.
• Credit sales is the total sold on credit during the period. Leave out cash sales.
• Days in the period is 30 for a month, 90 for a quarter or 365 for a year, as long as you use the same period for the sales figure.

An example from product sales

Say a chemicals distributor has $240,000 in unpaid invoices at the end of a quarter. Over the same 90 days, it sold $360,000 on credit.

DSO = 240,000 ÷ 360,000 × 90 = 60 days

The distributor's terms are net 30, so customers are taking about twice as long as agreed. That points to a collection problem, which might be late reminders, disputed invoices or a few big accounts that always pay slowly.

How to read the number

• Compare it with your terms. A DSO close to your payment terms is healthy. A DSO far above them needs a look.
• Watch the trend. A DSO that creeps up month by month matters more than one high month.
• Compare like with like. Industries and customer mixes differ, so compare your DSO with your own past figures first.
• Look underneath. An average hides the cause. Check which accounts owe the most and how old their invoices are.

This is a general explanation, not financial advice. Your accountant can tell you how to calculate it for your books.

How to bring DSO down

Most of the fix is process, and much of it sits with sales:

• Agree the payment terms on the quote and the order, so the customer knows them before shipping.
• Send a friendly reminder before the due date, not only after it. Our payment reminder email templates cover the wording.
• Follow up quickly on disputes, since an invoice in question is rarely paid.
• Check a new customer before offering terms. See what a credit limit is.

For the full routine, read how to chase overdue payments.

Related terms

• Net 30: the payment term DSO is usually measured against.
• Credit limit: how much credit a customer can have.
• Sales order: the record that leads to the invoice.

How PromptLab handles it

DSO is a finance calculation, so work it out from the receivables in your accounting system. PromptLab holds the sales side of collection: invoices created from a sales order, the payment terms on the order, notes on the account, tasks for follow-ups, and email, WhatsApp and Telegram in one shared Inbox. That is where payment chasing happens, so the history of who promised what is in one place.

Frequently asked questions

What is a good DSO?

There is no single good number. Aim for a DSO close to your payment terms, and compare it with your own history. A company on net 30 terms with a DSO of 35 is in a better place than one with a DSO of 60.

How do you calculate DSO?

Divide accounts receivable by credit sales for the period, then multiply by the number of days in that period. With $240,000 owed and $360,000 of credit sales over 90 days, DSO is 60 days.

Should cash sales be included in DSO?

No. DSO measures how long credit sales take to collect, so use credit sales only. Including cash sales makes the number look better than it is.

Is a lower DSO always better?

Usually, since cash arrives sooner. But very tight terms can cost you sales to competitors who offer longer ones, so the aim is a DSO that matches your terms, not the lowest possible figure.

Who is responsible for DSO, sales or finance?

Both. Finance sends invoices and tracks balances, while sales owns the customer relationship, agrees the terms and often has the conversation that gets an invoice paid.