DSO (Days Sales Outstanding), also referred to in French as délai moyen de paiement (DMP) or number of days of customer credit, is an essential indicator in financial management. A company’s financial strength largely depends on its ability to collect invoices within controlled timeframes, before facing cash outflows that could weaken its position. DSO therefore represents a continuous optimization lever to improve cash flow and reduce the risk of unpaid invoices.
DSO: Definition and Role in Financial Management
The average collection period corresponds to the time elapsed between the issue of an invoice and its actual collection. In practice, DSO represents the average number of days during which invoiced revenue has not yet been received. The lower this indicator, the healthier the company’s financial position is considered to be.
Beyond its numerical value, DSO helps to:
- Monitor financial health: A high DSO may indicate liquidity issues.
- Improve cash flow management: Reducing DSO strengthens cash inflows.
- Support strategic decision-making: DSO analysis helps adjust customer credit policies and collection processes.
DSO also plays a role in calculating Working Capital Requirement (WCR), specifically in the accounts receivable component. A lower DSO leads to a reduced WCR, while a longer DSO increases the risk of cash flow gaps.
Reducing DSO is therefore a recurring objective for finance departments and should be analyzed alongside DPO (Days Payable Outstanding) to assess urgency levels.
DSO and DPO: a key balance for cash flow
DPO, or Days Payable Outstanding, refers to the average time taken to pay suppliers. It indicates the number of days a company has to settle its supplier invoices. Outside of specific financial difficulties, these payment terms are generally subject to negotiation, sometimes on a recurring basis.
The relationship between DSO and DPO is direct: having a short collection period and a longer supplier payment period supports healthy cash flow. Conversely, when these two indicators converge, the risk that a simple delay could create financial strain increases. A DPO lower than the DSO clearly represents an unfavorable situation. In such cases, the company must pay its suppliers before collecting from its customers, which implies relying on external financing, an option that should be limited as much as possible.
It is therefore recommended to regularly recalculate and analyze the gap between DSO and DPO, in order to account for the addition of new customers or suppliers, as well as to anticipate potential contract renegotiations or reduce (BFR) working capital requirements (WCR).
Methods for Calculating DSO
DSO can be calculated using two different approaches. The first is simple but focuses on a specific period, while the second accounts for seasonal business fluctuations.
1. Accounting Method
The most commonly used method calculates the ratio between accounts receivable and total revenue (including tax) over a defined period (e.g., 30 or 90 days).
Formula:
Accounts receivable (incl. tax) / Revenue (incl. tax) × number of days in the period
While this method quickly provides an average collection period, it has limitations for businesses with strong seasonality. Monthly comparisons may be misleading, and annual calculations may cover too long a timeframe to effectively guide financial strategy.
However, it helps distinguish between:
- Current receivables: Within agreed payment terms
- Overdue receivables: Resulting from late payments, requiring stronger collection actions
2. Countback Method (Sales Exhaustion Approach)
This second approach reconstructs DSO by going backward in time and progressively allocating revenue from previous months to accounts receivable. The goal is to identify how many days of sales are needed to cover all receivables.
Example:
A company has €100,000 in receivables at the end of November. November revenue (€50,000 over 30 days) covers half of this amount.
The remaining €50,000 is partially covered by October revenue (€40,000 over 31 days), leaving €20,000 outstanding.
Going back to September, monthly revenue (€60,000) covers the remaining balance in one-third of a month, or 10 days.
DSO calculation:
30 + 31 + 10 = 71 days
The company therefore takes 71 days to collect its receivables, taking monthly revenue fluctuations into account.
This method is more accurate but also more complex to implement.
How to Improve Your DSO: Key Levers
Improving DSO relies on several actions that should start as early as the contract negotiation phase. Defining appropriate payment terms and thoroughly assessing customer creditworthiness upfront helps limit future issues. Changing terms mid-contract is more difficult.
Best practices include:
- Negotiating shorter payment terms to quickly detect delays and trigger collection actions
- Requesting upfront deposits to reduce financial risk
- Implementing a proactive collection strategy, with regular or automated reminders (modern digital tools help ensure reliable tracking)
- Resolving disputes quickly to avoid unnecessary payment delays
- Using receivables financing (factoring), factoring in its cost to protect margins
Optimizing collections is the main lever for shortening payment cycles. A proactive approach, including reminders before due dates, generally delivers better results.
Outsourcing collections is also growing, allowing companies to delegate this strategic task to specialists.