PBM Reporting Transparency Act This bill requires the Medicare Payment Advisory Commission to report certain information about pharmacy benefit managers (PBMs) under the Medicare prescription drug benefit and Medicare Advantage. Specifically, the commission must report on trends in agreements between PBMs and prescription drug plans, the impact of any differences in agreements on out-of-pocket spending for enrollees and pharmacy reimbursements, and any appropriate recommendations. The commission must submit an updated report two years after its initial report.