Narrative
Underpayment is rarely fraud and almost never random. It runs in patterns, and the patterns repeat across every payor.
When a statement comes up light, the temptation is to imagine someone cooking the books. The reality is duller and more useful: systems are vast, automated, and built from templates, so the same handful of errors recur across deal after deal. Learn the patterns and an audit stops being a fishing trip, you arrive knowing the five places money leaks and check each one in turn. Six recurring patterns account for the overwhelming majority of findings. This is the auditor's standing checklist.