Medicare’s embrace of site-neutral payments could significantly reshape how hospital outpatient services are reimbursed, with major implications for provider revenue, care delivery strategy, and regulatory planning. Between Congress considering site-neutral payment reforms that could reduce Medicare hospital reimbursements by upwards of $150B over a decade, and the Centers for Medicare & Medicaid Services (CMS) proposing to equalize payments for drug administration at hospital outpatient departments (HOPDs) and physician offices, it is clear that momentum toward site neutrality is accelerating. Our Site-Neutral Payment Calculator simulates payment differentials under one version of site-neutral payment reform, in which Medicare payments to HOPDs would equal the lower of Physician Fee Schedule (PFS) Facility rate and PFS Non-Facility rate, applied to the combined professional and technical payment for each. For a simulated HOPD orthopedic practice, the impact of this reform would be devastating, leading to a potential loss of 86 percent of Medicare revenue. Much of this revenue loss comes from CPT 29881 (Knee Arthroscopy), which would see its reimbursement fall from $3,602 to $518, an 85 percent reduction driven by the removal of the technical payment of $3,084. Of course, instead of this worst-case scenario, CMS could lower the HOPD technical payment to the ambulatory surgery center (ASC) facility rate, which would still incur a significant revenue hit. No matter which version of site-neutral reform takes hold, high-technical surgical services will face the greatest exposure, as site neutrality would align total reimbursement to a much-lower benchmark than HOPD facility costs.