(1) Except as provided in paragraph (2) of this definition, “business associate” means, with respect to a covered entity, a person who:
(i) On behalf of such covered entity or of an organized healthcare arrangement (as defined at 45 C.F.R. Sec. 164.501) in which the covered entity participates, but other than in the capacity of a member of the workforce of such covered entity or arrangement, performs, or assists in the performance of:
(A) A function or activity involving the use or disclosure of individually identifiable health information, including claims processing or administration, data analysis, processing or administration, utilization review, quality assurance, billing, benefit management, practice management, and repricing; or
(B) Any other function or activity regulated by this subchapter; or
(ii) Provides, other than in the capacity of a member of the workforce of such covered entity, legal, actuarial, accounting, consulting, data aggregation (as defined in Sec. 164.501 of this subchapter), management, administrative, accreditation, or financial services to or for such covered entity, or to or for an organized healthcare arrangement in which the covered entity participates, where the provision of the service involves the disclosure of individually identifiable health information from such covered entity or arrangement, or from another business associate of such covered entity or arrangement, to the person.
(2) A covered entity participating in an organized healthcare arrangement that performs a function or activity as described by paragraph (1)(i) of this definition for or on behalf of such organized healthcare arrangement, or that provides a service as described in paragraph (1)(ii) of this definition to or for such organized healthcare arrangement, does not, simply through the performance of such function or activity or the provision of such service, become a business associate of other covered entities participating in such organized healthcare arrangement.
(3) A covered entity may be a business associate of another covered entity.
NIST SP 800-66 Rev. 1
(45 C.F.R., Sec. 160.103)