Run a two-number receivable stress test before a customer's insolvency becomes your cash problem

One customer can become your second bank account

If you read the bank balance daily, you know a receivable is not cash until it lands. A large customer can look like growth while quietly becoming a claim on your runway.

The Atradius 2026 North America Payment Practices Barometer covered more than 600 firms across the United States, Canada and Mexico. On average, firms in that survey made 43 percent of B2B sales on credit terms. On average, overdue B2B invoices made up 23 percent of receivables. About one in three North American businesses said their cash availability had fallen. Suppliers most often pointed to customer liquidity constraints when explaining delayed B2B payments.

For a bootstrapped founder, that mix matters because you fund operations and your own pay from current revenue. A large receivable slipping past due can force you to touch cash reserves. The test is whether your books can survive the gap between the invoice and the payment.

Two numbers show whether one customer can break you

Run a two-number receivable stress test before a customer's insolvency becomes your cash problem. The first number exposes concentration that can hide in a healthy month. The second number shows how a payment delay can turn into a payroll problem.

Do not use profit for the second number. Use cash on hand plus collections you expect to receive, then subtract fixed costs you must pay. Treat the unpaid largest receivable as a cash gap. That is where a customer's liquidity problem becomes your working capital problem.

A bad-debt reserve gives you a number to defend when you tighten terms. A late payment can become a write-off you did not plan for. Once your largest customer is also your largest receivable, the reserve is not optional.

A short checklist keeps the next invoice from becoming a cash gap

Each item is a tripwire. You are trying to keep one account from becoming the reason your payroll is late, not to predict a customer's failure.

• Calculate the top-five customer share of last quarter's revenue. Flag the account after one customer is large enough to change the number.
• Estimate days of fixed costs covered with the largest receivable at 60-plus days past due.
• Compare that number to your runway. Tighten terms before the next order if it falls below the level you can survive.
• Set a bad-debt reserve for overdue receivables. Treat it as a real cost.
• Review the test after changes in a customer's payment behavior, a new large account, or rising fixed costs.

Keep the test short. If it needs a spreadsheet full of tabs, you will not run it with a low bank balance. A simple check is more useful than a complex model you abandon. Slower growth is a deliberate choice because it protects payroll.

Keep the test tied to the customer, not to the whole company. A small business cash flow can look healthy while one account holds a large share of revenue. A rising top-five share should pull the second number down, because more of your revenue is now tied to one balance sheet.

Nearly half of North American suppliers reported bad debt under 1 percent of receivables, and fewer than one in four reported it above 2 percent. That distribution is a useful anchor. It says most companies keep write-offs low, but a meaningful minority face heavier losses. Your reserve should reflect that risk, not ignore it.

Among North American companies, more than one in four expected insolvencies to rise. That expectation does not mean every customer will fail. The cost of being surprised is high enough to justify a regular check. Slow payment from your top customer should trigger a decision about terms, deposits, or smaller orders.