; treatment The amendment made by subparagraph (A) shall take effect on September 30, 2017, and shall apply with respect to any open claims, including claims generated or filed, after such date. (2) Clarification of definitions applicable to third party liability (A) In general Section 1902 of the Social Security Act ( 42 U.S.C. 1396a ) is amended by adding at the end the following new subsection: (nn) Responsible Third Party and Health Insurer Definitions For purposes of subsection (a)(25) and section 1903(d)(2)(B): (1) Responsible third party The term responsible third party means a health insurer, a pharmacy benefit manager to the extent the pharmacy benefit manager provides information under this title for the purpose of coordinating benefits, an accountable care organization under section 1899, or any other party that is, by statute, contract, or agreement, legally responsible for payment of a claim for a health care item or service. Such term does not include a party if payment by such party has been made or can reasonably be expected to be made under a workmen’s compensation law or plan of the United States or a State, or under an automobile or liability insurance policy or plan (including a self-insured plan), or under no fault insurance. (2) Health insurer The term health insurer means a group health plan, as defined in section 607(1) of the Employee Retirement Income Security Act of 1974, a self-insured plan, a fully-insured plan , a service benefit plan, a medicaid managed care plan under section 1903(m) or 1932, and any other health plan determined appropriate by the Secretary. . (B) Conforming amendments Section 1902(a)(25) of the Social Security Act ( 42 U.S.C. 1396a(a)(25) ) is amended— (i) in subparagraph (A), in the matter preceding clause (i), by striking third parties and all that follows through item or service) and inserting responsible third parties ; (ii) in subparagraph (G), by striking health insurer and all that follows through item or service) and inserting responsible third party