H.R. 8129 — To amend title XVIII of the Social Security Act to establish a full risk ACO program.

This section establishes a Full Risk Accountable Care Organization (ACO) Program under Medicare fee-for-service (Traditional Medicare), to be implemented by June 30, 2026, with standard and complex care tracks for groups of providers and suppliers (e.g., ACO professionals in group practices or networks, hospitals, critical access hospitals billing under Method II, rural health clinics, federally qualified health centers, and certain teaching hospitals) to manage and coordinate care for assigned beneficiaries. To participate, an ACO must (1) bear full financial risk with a commensurate guarantee mechanism; (2) serve a minimum number of assigned beneficiaries—at least 2,500 for standard ACOs or 250 in year one (rising to 500 in year two and 1,000 thereafter) for complex care ACOs; (3) enter a five-year agreement with the Secretary (renewable); (4) provide individualized care such as coordinated care transitions, social supports, behavioral health, nonvisit-based care, in-home care, and palliative care; and (5) meet Secretary-specified quality standards prioritizing patient experience and outcomes (with complex care ACOs also measured on "Days at Home"), while being exempt from the Merit-based Incentive Payment System. (As background, accountable care organizations originated in the Medicare Shared Savings Program to promote care coordination, quality improvement, and cost savings in fee-for-service Medicare; this program creates a permanent full-risk option beyond time-limited pilots, enabling capitated or incentive payments, preferred provider arrangements, and TIN-NPI level participation to support advanced primary care, especially for beneficiaries with six or more chronic conditions.)