Section 45, part 162 of the Code of Federal Regulations contains the Final Rule on health care provider identification numbers. To facilitate an efficient medical billing and reporting system, and to create an easily searchable database of providers and patient records, the government has created a system of standard codes to replace the previous program-specific codes. The Medicare legacy number is a code specific to Medicare that identified service providers on claims. The number was temporarily used along with the new code system during a limited dual-use period, but has since been superseded.


The Health Insurance Portability and Accountability Act of 1996 (HIPAA) mandated the creation of a standard set of codes identifying health care providers and procedures. The purpose was to facilitate portability of health records while maintaining patient privacy. The HIPAA code for health care providers, called the National Provider Identifier, or NPI, is a 10-digit number that replaces old identifier codes, which have come to be called legacy numbers. NPIs were first issued on May 23, 2005.


Before HIPAA, Medicare service providers were identified by a Provider Transaction Account Number, or PTAN. In May 2007 this number was rechristened as the Provider Identification Numbers (PIN), and was still used in some Medicare transactions. Both terms are still occasionally used, and both refer to the same number, which is also the same number referred to by the term “legacy number.” These legacy numbers, which were specific to Medicare only, have been replaced by the NPI numbers.

Dual Use Period

To facilitate the transition to the new NPI reporting system, the federal government created a dual-use period from October 1, 2006, to May 22, 2007. During this time, health care providers were encouraged to report both their new NPI number and their legacy number (PTAN) to create links within the system between the numbers and the medical records that contained them.


As of July 1, 2007, Medicare was authorized to reject claims that did not include the NPI number for the service provider. Use of the legacy number was still permitted for an indefinite period of time, but all claims must now be submitted with the NPI regardless of whether the legacy number is also included. The legacy numbers were gradually phased out until the official end of the dual-use period on December 17, 2007.


On September 21, 2007, the Department of Health Care Services (DHCS) deactivated healthcare providers that had not submitted a claim or received reimbursement in the previous year. Only those providers who had submitted claims under the new NPI system remained active at the end of the dual use system. Suppliers and service providers are still permitted to use legacy numbers on internal documents and transactions, but all reporting for tax, claim or reimbursement purposes must be done with the NPI number only.