How DSO is calculated
DSO = (accounts receivable ÷ revenue) × days in period
DSO tells you, on average, how many days it takes to collect payment after a sale. A DSO of 30 means you collect within 30 days of invoicing. A DSO of 60 means it takes two months on average.
Choosing the right period: Use the same period for both revenue and the number of days. Monthly revenue → 30 days. Quarterly revenue → 90 days. Annual revenue → 365 days. Using annual revenue with 30 days, or monthly revenue with 365 days, will produce a meaningless result.
DSO benchmarks
| DSO range | Rating | What it suggests |
|---|---|---|
| ≤30 days | Good | Collections are fast; minimal cash tied up in receivables |
| 31–45 days | Fair | Within net-30 to net-45 terms; room for improvement |
| 46–60 days | Slow | Customers are paying late or terms are too long; investigate |
| >60 days | Concern | Significant cash flow risk; collections process likely needs attention |
These are general benchmarks. Industry norms vary: B2B professional services often runs 45–60 days because clients expect 30–45 day terms and pay slowly. Government contracting regularly exceeds 60 days. Retail and restaurants are near zero because customers pay at point of sale.
Cash impact of improving DSO
Each day of DSO improvement frees up an amount equal to one day's revenue. If your daily revenue is $3,333 and you cut DSO by 10 days, you free up $33,330 in cash — permanently, as long as you maintain the improvement. That cash can pay down a line of credit, fund payroll, or support growth without new borrowing.
Worked examples
Example 1 — marketing agency: A marketing agency invoices $120,000 per month and has $180,000 in outstanding AR at month end.
| Item | Value |
|---|---|
| AR balance | $180,000 |
| Monthly revenue | $120,000 |
| DSO | ($180,000 ÷ $120,000) × 30 = 45 days |
| Daily revenue | $120,000 ÷ 30 = $4,000 |
| Cash freed if DSO → 30 days | 15 days × $4,000 = $60,000 |
Cutting DSO from 45 to 30 days would permanently free $60,000 in cash — enough to eliminate a line of credit balance or fund a quarter of payroll without borrowing.
Example 2 — construction subcontractor: A plumbing subcontractor bills $300,000 per quarter and carries $200,000 in AR.
| Item | Value |
|---|---|
| AR balance | $200,000 |
| Quarterly revenue | $300,000 |
| DSO | ($200,000 ÷ $300,000) × 90 = 60 days |
A 60-day DSO is not unusual in construction, where general contractors often pay on pay-when-paid terms. But it means the business is effectively financing two months of revenue for its customers. Invoice factoring — selling those receivables to a factor for immediate cash — is one tool for subcontractors in this position. See the invoice factoring calculator to estimate the cost.
Assumptions and limitations
- Uses ending AR balance, not average. The most common DSO formula uses the AR balance at the end of the period. Some analysts use the average of beginning and ending AR to smooth out seasonal spikes. If your business is highly seasonal, the average method gives a more representative result.
- Revenue should be credit sales only. Technically, DSO should use credit sales (invoiced sales) rather than total revenue, because cash sales have DSO of zero by definition. For businesses that bill exclusively, total revenue and credit sales are the same. For mixed cash/credit businesses, using total revenue understates DSO.
- A single period DSO can be misleading. Slow collection in the last week of a month can inflate month-end DSO without reflecting a systemic problem. Tracking DSO over multiple periods gives a clearer picture than a single calculation.
Frequently asked questions
- Why does my DSO matter to a lender?
- High DSO means a large proportion of your assets are tied up in uncollected invoices — which affects both your working capital ratio and your cash available to service debt. A lender sees slow collections as a credit risk: if customers start paying even more slowly or default, the business's liquidity deteriorates quickly. For invoice-based businesses seeking a line of credit, lenders often set a borrowing base on receivables aged under 90 days, so a high DSO directly limits how much you can borrow.
- How do I reduce DSO?
- Six proven levers: (1) invoice immediately after delivery, not on a weekly batch schedule; (2) shorten payment terms from net-45 to net-30; (3) offer a small early-payment discount (1–2%); (4) send reminder emails 5 days before due and the day of; (5) require deposits or progress payments for large projects; (6) use ACH auto-pay or credit card on file instead of waiting for a check.
- What is the difference between DSO and AR turnover?
- AR turnover ratio = revenue ÷ AR (a higher number is better). DSO = (AR ÷ revenue) × days (a lower number is better). They measure the same thing from opposite angles. DSO is expressed in days, which most people find more intuitive: "we collect in 35 days" is clearer than "our turnover ratio is 10.4×."
Sources
- Investopedia — "Days Sales Outstanding (DSO): Definition and How To Use It" (accessed 2026-10-04)
- Corporate Finance Institute — "Days Sales Outstanding" (accessed 2026-10-04)