A Provider Transaction Access Number (PTAN) is a unique identifier assigned by CMS to allow electronic billing and processing of Medicare claims. A National Provider Identifier (NPI) is a unique 10-digit identification number issued by the National Plan and Provider Enumeration System (NPPES) for use in administrative and financial transactions involving healthcare providers and suppliers. While a PTAN is specific to Medicare, an NPI can be used for various healthcare transactions, including Medicare, Medicaid, and private insurance.