This is the second in our client advisory series on accountable care organizations (“ACOs”), focusing on ACO legal structure and governance. On Oct. 20, 2011, CMS released the Final ACO Rules (“Final Rules”) implementing the voluntary Medicare Shared Savings Program for ACOs, pursuant to Section 3022 of the Patient Protection and Affordable Care Act (“ACA” or the “Act”). The ACA provides for the creation of an ACO comprised of physicians, hospitals, and other healthcare suppliers, willing to enter into a three-year shared savings program agreement with CMS and be accountable for the care of at least 5,000 Medicare beneficiaries. In the area of legal structure and governance, the basic requirements from the Proposed Rules did not change: (1) the form of entity must be recognized under state law; and (2) the ACO must have a tax identification number (“TIN”). CMS has, however, expanded the list of eligible ACO participants and provided additional guidance on governance.