42 CFR § 425.104 - Legal entity.
(a) An ACO must be a legal entity, formed under applicable State, Federal, or Tribal law, and authorized to conduct business in each State in which it operates for purposes of the following:
(1) Receiving and distributing shared savings.
(3) Establishing, reporting, and ensuring provider compliance with health care quality criteria, including quality performance standards.
(4) Fulfilling other ACO functions identified in this part.
(b) An ACO formed by two or more ACO participants, each of which is identified by a unique TIN, must be a legal entity separate from any of its ACO participants.