PBM auditing involves retrospectively reviewing claims to validate compliance with contracts and benefit plans. It helps identify issues and future changes. Auditing is important for several reasons: it fulfills fiduciary responsibilities; provides an impartial view of PBM performance; and contributes to reducing overall healthcare costs as pharmacy costs and utilization increase. Common areas reviewed include pricing, benefit design, fraud/waste/abuse, and guarantees/rebates. Audits commonly find disputes over contract interpretations and issues like incorrect copays, quantities, and rebate calculations. Recovered amounts vary depending on the type of issue identified. Examples of past audit findings include guarantee calculation errors, formulary noncompliance, and unclaimed rebates totaling over $1 million