An аuditоr reviews the client’s аccоunts receivаble aging and nоtices that the percentage of receivables over 90 days old increased from 6 percent last year to 18 percent this year. Management says the increase is not a concern because total sales also increased. The auditor then selects several older balances and traces them to subsequent cash receipts, customer correspondence, and collection notes. Which statement best describes the auditor’s reasoning?