Sales wants to offer 45-day terms to win a EUR 120k account—is that affordable?
Model the DSO and CCC impact first. At EUR 400k monthly revenue, ten extra days ties up roughly EUR 130k in receivables. Check overdraft headroom before you approve.
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DSO
DSO: plain-English definition, formula, worked example, how to interpret the result, peer-based benchmark guidance, common mistakes, and management actions in the ZBI Business Control Library.
What is DSO?
Days Sales Outstanding tells you how long customer invoices sit before cash lands. I calculate it every month because the ageing report alone does not normalise for revenue swings—a EUR 95,000 receivables balance means something different at EUR 400,000 monthly revenue than at EUR 250,000. For a components wholesaler billing on net-30 terms, DSO is the single number finance and sales can argue about without re-reading every open invoice. Get the revenue basis and period consistent; a spike in month-end shipments without collections will push DSO up even when customers are behaving.
Why DSO matters
Cash hits the overdraft before anyone says 'collections problem.' DSO drifting from 30 toward 45 days on EUR 400,000 monthly revenue ties up roughly EUR 50,000 extra working capital you could have used for stock or wages. Sales feels it when credit holds block shipments to slow payers you were afraid to chase. Let DSO run while you push revenue and you end up profitable on paper with suppliers calling about overdue payables because the bank line is full. Customers do not notice DSO directly—they notice when you tighten terms or stop accepting their orders on account.
Formula and variables
DSO = (Accounts Receivable ÷ Revenue) × Days in Period
Accounts receivable — trade debtors at period end; exclude unrelated balances.
Revenue — credit sales in the same period as the receivables context (often 90-day rolling revenue for stability).
Days in period — 30 for monthly, 90 for quarterly, 365 for annual.
Excel: =IFERROR(B2/B3*B4,0)
Real business example
Adria Components d.o.o., a EUR 4.8M industrial wholesaler in Osijek, runs monthly DSO. Receivables at month-end EUR 95,000; revenue for the month EUR 400,000; days in period 30. Simple DSO ≈ 7.1 days—misleading on its own because it uses one month's revenue against point-in-time receivables. Their rolling calculation shows DSO 38 days against net-30 terms. Two regional accounts pay at 55–60 days. Finance prioritises calls to those accounts before approving a EUR 80,000 stock purchase the buyer requested.
How to interpret the result
DSO only makes sense beside the ageing report and the terms you actually granted.
- DSO up and overdue percentage climbing means your collection process failed, not that 'customers are slow everywhere.'
- Match revenue net of returns to receivables; mixed bases give false comfort.
- One large customer can hold headline DSO flat while concentration risk builds.
- DSO eight or more days above contracted terms means enforce, renegotiate, or cut exposure.
Benchmark context
Benchmark against the payment terms you grant—net 30, net 45—not a universal day count from a textbook. Your six-month trend matters more than a peer average from a trade survey. A distributor selling mostly to large retailers will run different DSO than one serving cash-strapped SMEs. Improvement means overdue balances shrinking while DSO holds or falls, not hitting a low DSO by refusing all credit sales.
Red flags
- Rolling DSO above contracted terms for two consecutive months—expect EUR 30k–50k+ trapped cash at EUR 400k monthly revenue scale.
- Overdue above 60 days growing while headline DSO looks stable—concentration in a few accounts masks portfolio deterioration.
- DSO drops sharply at month-end after a large write-off—celebrating a number that reflects lost revenue, not better collections.
- Sales revenue up 15% but DSO up 10 days—growth is self-financing on your overdraft.
- Credit holds rising while DSO flat—terms enforcement starting; fix root cause before customers churn to competitors offering easier credit.
Common mistakes
- Using gross revenue while receivables exclude credit notes.
- Ignoring unallocated customer receipts sitting in suspense.
- Calculating DSO once at year-end instead of tracking monthly trend.
- Letting sales offer 60-day terms verbally while finance models on net 30.
- Comparing subsidiaries with different billing calendars without adjustment.
What should management do next?
- Review top 20 overdue accounts weekly with a named owner and committed call date.
- Auto-hold shipments when accounts exceed terms by more than seven days unless sales director overrides in writing.
- Publish DSO and overdue percentage on the same report sales sees before month-end commission calculation.
- Align new customer credit limits to payment history; reduce limits when DSO on that account exceeds terms twice.
- Model cash freed from a five-day DSO improvement using the ZBI cash-flow calculator before the next stock buy.
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FAQ
Why is my simple monthly DSO 7 days but rolling DSO 38 days?
Different methods. Simple month-end math divides one month's receivables by one month's revenue; rolling smooths seasonality. Use rolling for management; explain both to the bank if they ask.
Should I withhold commission on invoices over 60 days overdue?
Many owners do. Tie a portion of sales variable pay to collected cash or ageing buckets so DSO is not finance's problem alone.
Can I improve DSO without losing customers?
Yes—start with accounts already past terms, offer early-pay discount on selected invoices, and fix billing errors that delay payment. Do not tighten terms on your best payers.
When do I escalate a customer from 'slow payer' to legal or credit insurance claim?
When balance exceeds EUR 10k–15k and passes 90 days overdue with no documented payment plan, or when their DSO trend breaks your concentration limit.
Summary
DSO shows how fast revenue becomes cash. Track it monthly against your terms and ageing, and act on overdue accounts before working capital silently expands.
Reviewed by ZBI Business Control Library · Last updated 2026-06-15