; (2) by striking ACOs .—The Secretary and inserting ACOs .— (1) In general Subject to paragraph (2), the Secretary ; and (3) by adding at the end the following new paragraph: (2) Providing flexibility (A) Choice of prospective assignment For each agreement period (effective for agreements entered into or renewed on or after January 1, 2020), in the case where an ACO established under the program is in a Track that provides for the retrospective assignment of Medicare fee-for-service beneficiaries to the ACO, the Secretary shall permit the ACO to choose to have Medicare fee-for-service beneficiaries assigned prospectively, rather than retrospectively, to the ACO for an agreement period. (B) Assignment based on voluntary identification by Medicare fee-for-service beneficiaries (i) In general For performance year 2018 and each subsequent performance year, if a system is available for electronic designation, the Secretary shall permit a Medicare fee-for-service beneficiary to voluntarily identify an ACO professional as the primary care provider of the beneficiary for purposes of assigning such beneficiary to an ACO, as determined by the Secretary. (ii) Notification process The Secretary shall establish a process under which a Medicare fee-for-service beneficiary is— (I) notified of their ability to make an identification described in clause (i)