How to Calculate Working Capital and Free Cash by Reducing DSO
Working capital ties up cash you have already earned. Formula, worked examples and 5 operational levers to reduce your DSO and release liquidity immediately.
Arthur G.
Working capital (or BFR in French) measures the cash a business needs to finance its operating cycle between paying suppliers and collecting from customers. For most B2B companies, accounts receivable represents the majority of working capital and therefore the most direct lever for releasing cash.
Reducing DSO by 10 days on €10M revenue frees approximately €270,000 in cash. No new sales, no external financing.
This guide explains how to calculate working capital, why DSO is its primary driver, and which operational levers improve it concretely.
What This Article Covers
- The working capital formula and how to interpret it
- The direct link between DSO and working capital
- Why high DSO is not always a collections problem
- The 5 most frequent operational causes
- Levers to reduce DSO without damaging client relationships
- How to measure the impact in euros of cash
Working Capital Formula
Working capital is calculated as:
Working Capital = Inventory + Accounts Receivable − Accounts Payable
For service and SaaS B2B companies without significant inventory, the formula simplifies to:
Working Capital ≈ Accounts Receivable − Accounts Payable
Positive working capital means the company is financing its operating cycle from its own funds. The higher it is, the greater the cash requirement.
Concrete example:
A SaaS company with:
- €2.5M in accounts receivable
- €600K in accounts payable
- 0 inventory
Working Capital = 2,500,000 − 600,000 = €1,900,000
That is €1.9M of cash already generated by the business but not yet available in the bank account.
The Link Between DSO and Working Capital
DSO (Days Sales Outstanding) is the average number of days between issuing an invoice and collecting payment. It is the primary driver of working capital on the receivables side.
DSO formula:
DSO = (Accounts Receivable ÷ Period Revenue) × Number of Days
Every day of DSO corresponds to approximately annual revenue ÷ 365 in tied-up cash.
Quantified impact on €10M revenue:
| DSO | Cash tied up in receivables |
|---|---|
| 30 days | €822K |
| 45 days | €1,233K |
| 60 days | €1,644K |
| 75 days | €2,055K |
Moving from 60 to 45 days DSO releases €411,000 of immediately available cash.
Why High DSO Is Not Always a Collections Problem
Most finance teams treat DSO as a collections problem. In reality, the causes are often further upstream.
The 5 most frequent operational causes:
1. Late invoicing
The DSO clock starts at the invoice date, not the delivery date. An invoice issued 5 days after the service delivery mechanically extends DSO by 5 days — before the client has even received anything.
2. Billing errors
A missing purchase order reference, an incorrect amount, or an invoice sent to the wrong contact blocks the client's internal approval workflow. The invoice remains unpaid not through bad faith, but because it cannot be processed.
3. Unresolved disputes
A disagreement about a deliverable, a price difference, or a pending credit note often blocks payment of the entire invoice, even when the undisputed portion could be settled.
4. Payment friction
If the client needs to log in to a portal, find a bank account number, or get internal sign-off before paying, each step adds days. A direct payment link on the invoice can alone reduce DSO by 5 to 10 days.
5. Late or generic reminders
A reminder sent 15 days after the due date to a client who had simply forgotten leaves 15 days of cash unnecessarily blocked. Automated reminders send the same message to everyone: regardless of history, amount or risk profile.
5 Operational Levers to Reduce DSO
Lever 1: Invoice immediately upon delivery
Connect your project management or CRM tool to your invoicing software to trigger issuance automatically upon milestone approval. Every day saved at this stage translates directly into fewer DSO days.
Lever 2: Validate billing information before delivery
Systematically confirming the accounting contact, purchase order reference and payment terms before issuing the invoice eliminates 90% of downstream administrative blockers.
Lever 3: Add a direct payment link to every invoice
The client can pay in 3 clicks without leaving their email. Payment rates within 48 hours increase significantly. The DSO impact is immediate and measurable.
Lever 4: Automate reminders by risk profile
Rather than a uniform calendar sequence, segment reminders by historical payment behaviour, amount and age. A reliable client 3 days late deserves a discreet nudge. A chronic late payer at 30 days requires immediate escalation.
Lever 5: Resolve disputes proactively
An unresolved dispute can block tens of thousands of euros for weeks. Proactively identifying disputed invoices, involving the right teams (sales, ops) and tracking resolution through to collection is one of the highest-impact actions on working capital.
How to Measure the Cash Impact
The conversion from DSO days to euros is direct:
Cash released = (DSO days reduced × Annual revenue) ÷ 365
Examples:
| Annual revenue | DSO reduction | Cash released |
|---|---|---|
| €5M | −10 days | ~€137K |
| €10M | −10 days | ~€274K |
| €20M | −10 days | ~€548K |
| €50M | −10 days | ~€1.37M |
This calculation transforms an operational metric into a board-level priority argument.
What This Means for Finance Teams
Reducing working capital through DSO does not require negotiating new commercial terms or accepting discounts. It means identifying where cash is getting blocked in the billing cycle and systematically eliminating those friction points.
Teams that combine fast invoicing, adapted reminders and proactive dispute resolution see DSO reductions of 15 to 30 days within the first 90 days, without changing contractual terms with their clients.
Frequently Asked Questions
What is the difference between working capital and DSO?
Working capital is a balance sheet metric that measures cash tied up in the operating cycle. DSO is an operational metric that measures the speed of invoice collection. DSO is the primary driver of working capital on the receivables side: reducing DSO mechanically reduces working capital.
Is negative working capital possible and desirable?
Yes. Negative working capital means clients pay before the company pays its suppliers: this is the model of large retailers and some annual prepaid SaaS businesses. It is a very comfortable cash position.
How long does it take to significantly reduce DSO?
With the right operational levers (fast invoicing, automated reminders, dispute resolution), first effects are visible within 30 to 60 days. A reduction of 10 to 20 days is realistic within the first 90 days for most B2B companies.