This legislation, titled the "Preventing Hospital Overbilling of Medicare Act," seeks to address incorrect billing practices by off-campus hospital outpatient departments. It primarily focuses on promoting site-neutral payments under Medicare by removing certain exceptions to the definition of an off-campus outpatient department, effective January 1, 2026. This includes eliminating the site-neutral exception for off-campus emergency departments, ensuring that services provided in these settings are reimbursed at rates comparable to non-hospital facilities. The bill clarifies the Secretary of Health and Human Services' authority to implement policies that reduce Medicare expenditures by preventing hospitals from billing for services furnished at off-campus locations as if they were provided at the main hospital. A key provision mandates that each off-campus outpatient department of a provider must be assigned a separate unique health identifier (NPI) from its parent provider by January 1, 2026. Hospitals will then be required to use this specific identifier on HIPAA X12 837P transactions or CMS 1500 forms when billing for services from these off-campus departments. Furthermore, the bill extends these billing requirements to other healthcare providers, prohibiting them from submitting claims or holding individuals liable for services at off-campus departments unless billed with the separate unique identifier on specified forms. To encourage broader adoption, the Secretary is also requested to ask the National Association of Insurance Commissioners (NAIC) to establish a model act or regulation. This model would allow health insurance issuers and group health plans to reject claims from off-campus departments that do not adhere to these new, standardized billing practices.