On November 20, 2020, the U.S. Department of Health and Human Services (HHS) Office of Inspector General (OIG) finalized a proposal to lower prescription drug costs by removing the safe harbor protection of drug manufacturer rebates under the Anti-Kickback Statute (AKS), creating a new safe harbor for price reductions reflected at the point of sale (POS). In this paper, we focus on the implications of potential changes to the Part D risk score mechanisms. Recalibration of prescription drug hierarchical condition categories (RxHCCs) for POS rebates could have disparate impacts on plan sponsors.