The MSSP 2026 Proposed Rule marks a significant shift as CMS moves ACOs toward full accountability. After years of gradual changes, CMS is transitioning ACOs from low-risk tracks to mandatory two-sided risk arrangements. This transformation affects 477 ACOs serving over 11.2 million Medicare beneficiaries.
This rule may be costly for ACOs that have not yet prepared for two-sided risk. Stricter quality reporting, updated beneficiary assignment rules, and operational adjustments across ACOs will all be impacted. The preparation window is limited, making early planning essential.
What Is the MSSP 2026 Proposed Rule Actually Changing?
CMS is accelerating the shift from one-sided risk (where ACOs share savings but not losses) to mandatory two-sided risk arrangements. The program has matured enough, in CMS’s view, that continued reliance on low-accountability tracks is no longer justified.
Here’s what’s changing at a high level:
- Risk track requirements are being tightened
- Beneficiary assignment rules are being adjusted
- Quality measures are being streamlined
- Monitoring of ACO performance is expanding
Who Does This Rule Affect Most?
Impact on Small and Rural ACOs
Smaller ACOs receive limited flexibility, but with strict conditions. ACOs are now required by CMS to reach a minimum of 5,000 beneficiaries only during the third benchmark year, as opposed to once per year. This provides emerging organizations with increased flexibility, particularly within underserved or rural markets.
However, if an ACO drops below 5,000 beneficiaries in any benchmark year:
- It must remain in the BASIC track
- It faces caps on both savings and losses
- It cannot participate in the ENHANCED track
- It loses access to benefits available for low-revenue organizations
So while the flexibility is real, the guardrails are firm.
What Are the Quality Measure Updates for 2026?
CMS is simplifying quality reporting. However, standards remain rigorous.
Key updates include:
- Health equity adjustment removed from ACO quality scores starting Performance Year 2025. CMS found it overlapped with existing incentives and added unnecessary complexity.
- The Social Determinants Screening measure (Quality ID 487) is removed from the APP Plus set, reflecting a more clinically-focused approach.
- Medicare Clinical Quality Measures now require beneficiaries to have received at least one annual primary care service.
- Behavioral health and psychiatric collaborative care management is now formally recognized as primary care, highlighting its role in value-based outcomes.
- Beginning in 2026, CMS will oversee both standard and alternative quality performance standards that will expand the oversight platform of all participating ACOs.
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What Does Two-Sided Risk Actually Mean for Your ACO?
In a two-sided risk model, ACOs will receive the upside (savings) and the downside (losses) in comparison with their benchmark. This is a departure from one-sided models where only savings were shared.
For ACOs used to operating in low-risk tracks, this requires:
- Stronger data integration across clinical and claims sources
- Proactive population health management rather than reactive care
- Continuous performance monitoring against benchmarks
- Strategic assessment of provider network strengths and gaps
Organizations that develop two-sided risk capabilities now will gain an early advantage in compliance and performance.
How Should ACOs Prepare Right Now?
Key areas for ACO preparation include:
- Audit your current risk track: Understand where you stand and when mandatory migration applies
- Invest in data infrastructure: Claims data is insufficient; clinical and social determinants data need to be combined.
- Strengthen quality reporting workflows: As CMS increases its monitoring, reporting loopholes will emerge fast.
- Engage your provider network: Adoption of risks can only be achieved when frontline providers are aware of the model and their part in the model.
- Partner with the right technology: Having a platform that links data, identifies high-risk patients at the initial stage, and automates the quality reporting is no longer a luxury.
Conclusion
The Proposed Rule of MSSP 2026 is a turning point. Voluntary and low-risk participation is being replaced by mandatory accountability; ACOs that delay preparation risk falling behind. The positive side is that those organizations that are investing in the data, technology, and models of proactive care today are the ones that will be the leaders tomorrow.
Why Choose Persivia?
Persivia is a provider of a digital health platform, CareSpace®, that provides ACOs with the visibility of population health, real-time quality reporting, and risk management features that they require to succeed under the new rules. This platform integrates EHR and claims data into longitudinal patient records, automates CQM submission, and identifies high-risk individuals early.
