What If Your Biggest Customer Pays Late?

Measure the concentration that affects this period

Start with outstanding invoices and expected receipt dates. Annual revenue concentration is useful, but it can miss a short-term problem: one customer may represent only a modest share of yearly sales and most of next fortnight's receipts.

In this fictional example, a customer owes $12,000 out of total trade receivables of $20,000: 60%. The remaining $8,000 is owed by other customers. Check whether any balances are disputed, overdue or dependent on acceptance paperwork before calling them reliable.

Assumptions: AUD. This is a snapshot of outstanding invoices, not annual sales share.

Customer group	Outstanding	Share
Largest customer	$12,000	60%
All other customers	$8,000	40%

Original ASBG worked example. All businesses, amounts and scenarios are fictional. The table contains the same figures as the visual.

Move the receipt by two weeks

Assumptions: AUD total bank movements, with no borrowing assumed. Opening cash $10,000. Other receipts are $4,000 and payments $9,000 in each of four weeks. Main customer pays $12,000 in week 1 in the base case, week 3 in the delayed case.

Week	Base receipt from main customer	Base closing cash	Delayed receipt	Delayed closing cash
1	$12,000	$17,000	$0	$5,000
2	$0	$12,000	$0	$0
3	$0	$7,000	$12,000	$7,000
4	$0	$2,000	$0	$2,000

Original ASBG worked example. All businesses, amounts and scenarios are fictional. The table contains the same figures as the visual.

Both cases end at $2,000, but the delayed case reaches zero in week 2. If the owner chooses a $2,000 minimum cash floor, the temporary shortfall against that floor is $2,000. Check payment days within each week too: a zero week-end balance leaves no room for a payment arriving earlier than expected.

Distinguish delay from possible non-payment

Ask whether the invoice was received, accepted and scheduled for payment. A missing purchase-order reference requires a different action from a customer disputing the work or reporting financial trouble.

If recovery is doubtful, run a case with no receipt within the forecast horizon. Don't keep moving it forward a week indefinitely. A forecasting scenario doesn't decide whether to write off a debt in the accounts or for tax; take that separate question to your accountant.

Act before the week-2 gap

Before week 2, the owner might confirm the payment with the customer, correct missing invoice information or examine genuinely optional spending. A proposal to change supplier payments needs agreement, not just a new spreadsheet date. Follow the unpaid-invoice guide for collection steps and keep the conversation factual.

Avoid adding uncertain new sales as the automatic solution. The pipeline guide separates accepted work from enquiries, and the cash-buffer worksheet helps plan for recurring exposure.

Update the case when evidence changes

Record who confirmed the payment, when and for what amount. Replace assumptions with cleared cash as it arrives. If the payer sends $5,000, forecast only the remaining $7,000, with its own evidence and timing.

Key takeaways

• Measure concentration in the receipts you need soon.
• Compare the lowest balances, not only the final week.
• Treat uncertain recovery differently from a confirmed short delay.

Where to get help

Use the cash-flow forecast template for the full business calendar. ASIC's creditor guidance explains warning signs when a company owing you money may be in financial trouble. Seek qualified advice if your own debts may become unpayable.