ACO REACH stands for Accountable Care Organization Realizing Equity, Access, and Community Health. It is a CMS Innovation Center model in which provider-led ACOs manage cost and quality for aligned traditional Medicare patients under capitated payment, with a required focus on health equity.

Both are Medicare accountable-care models, but ACO REACH uses capitated or partial-capitation payment with mandatory downside risk and an explicit health-equity requirement, while the MSSP is a broader, permanent program with tracks ranging from upside-only to two-sided risk. REACH is a time-limited Innovation Center model.

Under capitation the ACO keeps what it does not spend on avoidable care, so proactively reaching aligned patients to close gaps, manage chronic conditions, and follow up after discharge is central. The equity requirement makes reaching historically underserved patients a measured obligation, not just good practice.