"The purpose of the National Provider Identifier (NPI) is to uniquely identify a health care provider in standard transactions, such as health care claims. NPIs may also be used to identify health care providers on prescriptions, in internal files to link proprietary provider identification numbers and other information, in coordination of benefits between health plans, in patient medical record systems, in program integrity files, and in other ways. HIPAA requires that covered entities (i.e., health plans, health care clearinghouses, and those health care providers who transmit any health information in electronic form in connection with a transaction for which the Secretary of Health and Human Services has adopted a standard) use NPIs in standard transactions by the compliance dates. The compliance date for all covered entities except small health plans is May 23, 2007; the compliance date for small health plans is May 23, 2008. As of the compliance dates, the NPI will be the only health care provider identifier that can be used for identification purposes in standard transactions by covered entities."