Error Rate Findings and Results

The Part D Improper Payment Measurement (Part D IPM) Program identifies overpayment and underpayment errors in drug costs and low-income subsidy payments using data from Prescription Drug Events (PDEs). This review uses both prescription information and Part D sponsor claim information. The document available for download contains comprehensive data and details, including improper payment results and findings related to overpayments and underpayments. Download the FY 2025 Medicare Part D Error Rate Findings and Results (PDF) to access the complete analysis and supporting data. The information below defines key IPM terms for clarity and understanding.

Key Terms

Gross Improper Payments – The absolute value of the sum of overpayments and underpayments.

Overpayments – A CMS overpayment is any instance where the captured PDE information is greater than what is supported by the provided documentation. CMS compares details associated with the prescribed drug to the dispensed drug to the information supplied on a PDE record to identify any discrepancies where the sponsor received more payment than the documentation supports. Examples include when the prescribed medication is actually less expensive than the value reported on the PDE record or when the prescribed quantity is less than what was dispensed.

Underpayments – A CMS underpayment is any instance where the captured PDE information is less than what is supported by the provided documentation. CMS compares details associated with the prescribed drug to the dispensed drug and to the information supplied on a PDE record to identify any discrepancies where the sponsor received less payment than the documentation supports. Examples include when the prescribed medication is more expensive than the value reported on the PDE record or when the prescribed quantity, based on the submitted days’ supply, is greater than what was dispensed.

Monetary Loss – A subset of improper payments where the wrong recipient was paid or the correct recipient was paid the wrong amount. Monetary loss results from administrative or process errors by another party. In the Part D Program, monetary loss results from CMS payments being in excess of what the supporting documents validated.

Non-Monetary Loss – The non-monetary loss component comprises underpayments resulting from cases in which the supporting documentation validates a payment higher than what was paid by CMS, as identified during the PDE record review.