Amends subsection (f) of 42 U.S.C. 1396r-8 to (1) require the Secretary to conduct monthly surveys to determine national average drug acquisition cost benchmarks for retail community pharmacies and applicable non-retail pharmacies; (2) authorize use of vendors and specify vendor reporting and data-differentiation requirements; (3) require States to compel pharmacy participation in surveys; (4) require public reporting of survey information; (5) establish civil money penalties (including a per-violation cap) and applicability of section 1128A provisions; and (6) add oversight and an appropriation for the Office of Inspector General.

Adds new definitions to subsection (k) of 42 U.S.C. 1396r-8: paragraph (12) defining 'applicable non-retail pharmacy' and paragraph (13) defining 'affiliate.'

Adds a new section titled 'Oversight of entities that provide pharmacy benefit management services' establishing contract conditions, periodic reporting requirements (including required report contents and formats), privacy rules, public-disclosure limitations, definitions (e.g., applicable entity, contracted compensation, gross/net spending), and rulemaking authority.

Adds a new subsection (g) to treat references in section 4980D to a group health plan (and the reference to the employer in subsection (e)(1)) as including an entity providing pharmacy benefit management services where the requirement under section 9826 applies to that entity.

Clerical amendment to the table of sections for subchapter B of chapter 100 to add a new item for the newly added section on oversight of pharmacy benefit management services.

Strikes existing subparagraph (A) and inserts a new subparagraph (A) requiring PDP sponsors offering prescription drug plans to permit any pharmacy that meets standard contract terms to participate as a network pharmacy; requires contract terms to be reasonable and relevant for plan years beginning on or after January 1, 2029 and directs the Secretary to establish standards and issue a request for information to inform those standards.

Adds new subsections to require the Secretary to publish reports on essential retail pharmacies (definitions, data comparisons, and trends) beginning for plan years starting January 1, 2028, to publish a list of essential retail pharmacies on CMS's public website, to require PDP sponsors and MA organizations to submit affiliate lists and certain payment information, and to add a biennial report on enforcement and oversight actions (first due not later than 2 years after enactment and at least once every 2 years thereafter).

Conforming amendment to section 1857(g)(1): inserts a new subparagraph (K) identifying failure to comply with the standards for reasonable and relevant contract terms and conditions under section 1860D–4(b)(1)(A)(ii) as a basis for action; redesignates and updates cross-references to other subparagraphs accordingly.

Adds new paragraph (9) to require, for plan years beginning on or after January 1, 2028, that contracts between PDP sponsors and pharmacy benefit managers include a written agreement obligating the pharmacy benefit manager to reimburse the PDP sponsor for amounts the sponsor is required to pay to the Secretary as a result of violations related to delegated responsibilities.

Amends section 1857(f)(3) by adding a new subparagraph (F) to make the accountability provision in section 1860D–12(b)(9) applicable to M–plans for plan years beginning on or after January 1, 2028.