The Centers for Medicare & Medicaid Services (CMS) is currently navigating a period of unprecedented regulatory turbulence. For years, the Medicare Advantage (MA) Star Ratings program has served as the bedrock of the private Medicare market, dictating billions of dollars in quality bonus payments (QBPs) and serving as a critical differentiator for health plans competing for enrollment. However, a wave of successful litigation from health insurers has placed the agency’s methodology under a microscope, forcing a series of forced recalculations that threaten the stability of the entire rating ecosystem.
The most recent—and arguably most significant—chapter in this saga involves Clover Health, which successfully challenged the federal agency in court, triggering a ripple effect that has forced CMS to reconsider its 2026 Star Ratings. This legal friction is no longer just about arithmetic; it has evolved into a fundamental debate over administrative law, regulatory authority, and the transparency of the government’s oversight of the nation’s largest health insurance market.
The Chronology of Conflict: From Technical Errors to Legal Precedent
The friction between CMS and MA plans is not a new phenomenon, but the nature of the disputes has shifted dramatically. Historically, disputes over Star Ratings were largely confined to technical disagreements—the "math" of the scoring process, such as rounding conventions or data aggregation errors.
In recent years, however, the courtroom has become a secondary headquarters for insurance strategy. Major players such as SCAN Health Plan and Elevance Health successfully challenged CMS’s previous methodologies, resulting in a 2024 rating recalculation. These victories established a proof-of-concept for other insurers: if an insurer can prove that CMS failed to adhere to its own stated protocols, the courts may compel the agency to backtrack.
The trajectory reached a new inflection point in late May 2025. A federal judge ruled in favor of Clover Health, determining that CMS had improperly calculated the insurer’s ratings by incorporating 20 specific quality measures without the requisite statutory authority. Unlike previous cases, which focused on clerical or procedural execution, the Clover Health decision struck at the heart of the agency’s rulemaking process. The court concluded that CMS had relied on unauthorized data sources and failed to follow the mandatory notice-and-comment rulemaking process required under the Administrative Procedure Act.
Following this ruling, CMS announced a voluntary initiative to recalculate 2026 Star Ratings for select plans. For Clover Health, the impact was immediate and substantial: their rating was elevated from 3.5 to 4.5 stars. Clover had previously estimated that the lower rating would have resulted in a staggering $120 million shortfall in potential bonus payments, illustrating the massive financial stakes involved in these fractional changes.
Anatomy of the Legal Challenge: Why "Math" Isn’t the Only Problem
To understand why CMS is currently on the defensive, one must distinguish between a simple computational error and a systemic regulatory failure. Experts suggest that the recent legal successes are indicative of a deeper procedural vulnerability.
"This was not a math error, and that distinction matters," explains Esteban Lopez, a partner in West Monroe’s Healthcare & Life Sciences practice. "The court took issue with how CMS got to its numbers, including the data sources it relied on and its decision to fold in certain measures without going through proper notice-and-comment rulemaking. The problem was CMS’s legal authority and process, not whether the underlying quality topics are worth measuring."
This distinction is crucial for the industry. While previous challenges looked at the minutiae of rounding or data collection, the Clover case challenged the very legitimacy of the metrics themselves. Ari Gottlieb, principal of A2 Strategy Corp, notes that this represents a fundamental shift in strategy for health plans.
"Clover was able to succeed by making a really novel argument—that some of the measures were not authorized under the enabling statute and therefore they should never have been included," Gottlieb said. "That was a new argument that differed from what we’ve seen recently, which are more tactical things like the methodology around collecting the inputs to the measures."
Implications for the Medicare Advantage Landscape
The decision by CMS to offer voluntary recalculations is seen by many analysts as a defensive measure—a preemptive strike to avoid a flood of litigation from other MA plans that may have been similarly affected by the inclusion of unauthorized measures. However, the agency has set strict boundaries on this process: CMS will only perform a recalculation if it results in a higher score. If the math dictates a lower rating, the status quo remains.
Financial Volatility and the "Four-Star" Threshold
The financial implications for health plans are binary and severe. Because the Medicare Advantage bonus structure is heavily weighted toward plans with four or more stars, even a marginal change—such as a 0.5-star increase—can translate into millions of dollars in revenue.
"That kind of movement flows straight into quality bonus payments, rebates, the benefits a plan can offer, bid strategy, and where it stands against competitors," Lopez observed. "This is not a broad windfall, and plans should resist assuming it works in their favor until they have run their own numbers."
The Shifting Focus of Quality Metrics
As CMS faces these legal headwinds, the program is undergoing its own internal evolution. Dr. Sanjay Doddamani, founder and CEO of Guidehealth, points out that the agency is attempting to pivot toward more outcome-oriented metrics, moving away from administrative process measures.
For the 2027 cycle, CMS is removing several administrative burdens, such as metrics related to the timeliness of appeals and the availability of foreign language interpreters. While this simplifies the program, it creates a new type of risk. "When there is a smaller number of measures in the star rating calculations, there’s the potential for more variation because each measure carries more weight," Dr. Doddamani noted.
The Future of Oversight: Balancing Rigor and Stability
The current environment places CMS in a difficult position. The agency must ensure that the Medicare Advantage program incentivizes high-quality care, but it must do so within the rigid constraints of federal law. If the agency continues to be perceived as arbitrary in its selection of measures or opaque in its data sourcing, it will continue to face expensive and distracting litigation.
Industry observers remain divided on whether this is a temporary period of adjustment or a permanent shift in how CMS governs the MA market.
"Recalculating seemed to be the most prudent action CMS could take to sort of eliminate the potential for having 50 lawsuits filed against them," Gottlieb remarked. "The story isn’t over. We don’t really know how it’s going to end, but so far it looks like a pretty big win for Clover, in that they’re at least preserving or increasing their payment rate for 2027."
The Path Forward
For health plans, the lesson is clear: the era of blind reliance on CMS’s final rating output is over. Plans are increasingly investing in independent auditing and legal analysis to verify that their ratings align with the agency’s stated methodology and statutory authority.
As Dr. Doddamani summarizes, the ultimate goal for all stakeholders—CMS, payers, and the patients they serve—is stability. "[Reducing the number of measures] is not necessarily good or bad, but it does increase the importance of getting the methodology right and ensuring that the measures being used are meaningful, outcome-oriented, and reflective of better patient care," he said. "Health plans and providers alike value predictability and stability. As CMS continues to evolve the program, the challenge will be balancing simplicity, outcomes, and measurement rigor while maintaining confidence in the ratings system."
Until such a balance is struck, the Medicare Advantage Star Ratings program will likely remain a high-stakes legal battleground, where the difference between a successful fiscal year and a financial crisis is determined not just by the quality of care, but by the strength of the legal team auditing the government’s own processes.
