National Provider Identifier
The NPI is a 10-position, intelligence-free numeric identifier (10-digit number). This means that the numbers do not carry other information about health care providers, such as the state in which they live or their medical specialty. The NPI must be used in lieu of legacy provider identifiers in the HIPAA standard transactions.
As outlined in the Federal Regulation, physicians must share their NPI with other health care providers, health plans, clearinghouses, and any entity that may need it for billing purposes. The NPI furthers the goal of standardizing health care transactions between physicians, various payers and clearinghouses.