Section 425.401 - Criteria for a beneficiary to be assigned to an ACO(a) A beneficiary may be assigned to an ACO under the assignment methodology in §§ 425.402 and 425.404 , for a performance or benchmark year, if the beneficiary meets all of the following criteria during the assignment window: (1)(i) Has at least 1 month of Part A and Part B enrollment; and(ii) Does not have any months of Part A only or Part B only enrollment.(2) Does not have any months of Medicare group (private) health plan enrollment.(3) Is not assigned to any other Medicare shared savings initiative.(4) Lives in the United States or U.S. territories and possessions, based on the most recent available data in our beneficiary records regarding the beneficiary's residence at the end of the assignment window.(b) A beneficiary is excluded from the prospective assignment list of an ACO that is participating under prospective assignment under § 425.400(a)(3) at the end of a performance or benchmark year and quarterly during each performance year consistent with § 425.400(a)(3)(ii) , or at the end of CY 2019 as specified in § 425.609(b)(1)(ii) and (c)(1)(ii) if the beneficiary meets any of the following criteria during the performance or benchmark year: (1)(i) Does not have at least 1 month of Part A and Part B enrollment; and(ii) Has any months of Part A only or Part B only enrollment.(2) Has any months of Medicare group (private) health plan enrollment.(3) Did not live in the United States or U.S. territories and possessions, based on the most recent available data in our beneficiary records regarding the beneficiary's residency at the end of the year. 80 FR 32840 , June 9, 2015, as amended at 83 FR 60093 , Nov. 23, 2018; 83 FR 68069 , Dec. 31, 2018