Days Sales Outstanding

DSO is computed as accounts receivable divided by revenue, multiplied by the number of days in the measurement period. A company with $100 million in accounts receivable and $500 million in quarterly revenue has a DSO of approximately 18 days, meaning it collects on its invoices in about 18 days on average. An increase in DSO from one period to the next — holding the business mix constant — indicates that collection is taking longer, which can have multiple causes.

In fundamental analysis, changes in DSO are scrutinized as part of quality of earnings work. When a company's reported revenue growth outpaces its cash collections, DSO rises, and the gap between net income and operating cash flow widens. This pattern may indicate that the company is booking revenue from customers who are slow to pay or, in more serious cases, from sales that may not ultimately be collectible — a precursor to write-offs or revenue reversals in future periods.

For U.S. technology companies that sell enterprise software or services on annual contracts, DSO can fluctuate significantly based on invoicing timing and contract structure. Billings and deferred revenue metrics in software companies are often analyzed alongside DSO to build a complete picture of cash flow dynamics. Medical device and pharmaceutical companies also receive careful DSO scrutiny because their customers include hospital systems and distributors that sometimes face their own cash flow constraints.

Investors tracking DSO trends across multiple quarters can identify inflections that anticipate earnings problems. A sustained multi-quarter rise in DSO at a company reporting strong revenue growth is one of the classic warning signs flagged in academic research on earnings quality and financial statement analysis, including foundational work by professors Healy, Wahlen, and Dechow.