The sub-group initially started with the CMS draft taxonomy code set. This list incorporated all types of providers associated with health care in various ways, e.g., technologists or technicians who support or repair equipment/machinery, contractors, physicians, dentists, suppliers. A number of the providers offer health services, in concert with others, and do not or cannot bill independently for their services. The amount of research to validate and classify all providers using the proposed hierarchical structure was enormous. The X12N sub-group focused on health care providers who are licensed practitioners, those who bill for health-related services rendered, and those who appeared on the Medicare CMS Provider Specialty listing. This included providers who were licensed to practice medicine via state licensure agencies. In addition, a very broad definition of "areas of specialization" was used, which included nationally recognized specialties, provider self-designated specialties, areas of practice focus, and any request by any agency or trading partner submitted before the first taxonomy release. This level of detail captured specialty information in categories detailed enough to support those trading credentialing information, yet broad enough to support those wishing to trade directory level specialization information.
In 2001, X12N asked the NUCC to become the official maintainer of the Health Care Provider Taxonomy code set. The NUCC has a formal operating protocol, including the Code Subcommittee's processes. The NUCC is a diverse group of health care industry stakeholders representing providers, payers, designated standards maintenance organizations, public health organizations, and vendors.