Plans have taken CMS to court over the ratings, and won. This lesson covers the litigation that has destabilized the program.
When a quality score controls billions of dollars, the parties affected will eventually test its legal foundations. That is what has happened to Medicare Advantage Star Ratings, and the results have been striking enough to reshape the program.
The wave of litigation
A long list of insurers has challenged how CMS calculates ratings, including UnitedHealthcare, Humana, Elevance, Alignment Health, Centene, SCAN Health Plan, and several Blue Cross plans. The disputes are not symbolic. CareFirst BlueCross BlueShield sued over an estimated $32 million in lost quality bonus payments, and Elevance’s dispute with CMS involves roughly $115 million.
The Clover decision
The most consequential ruling came in Clover Insurance Company v. HHS, where in May 2026 a Georgia federal court threw out twenty measures CMS had used in calculating 2026 Star Ratings. The court’s reasoning splits neatly in two:
| Ground | Measures affected |
|---|---|
| Based on data sources the Medicare Act does not authorize CMS to consider | 10 |
| Adopted without the required notice-and-comment rulemaking | 10 |
Worth remembering: the second half of that ruling is the rulemaking course made real. Ten measures fell not because they were bad measures but because CMS imposed them without going through notice-and-comment. When an agency attaches binding financial consequences to a requirement, the procedure it used to adopt that requirement is itself legally load-bearing, and a party with money at stake can and did enforce that. Process is not a formality.
CMS recalculated the 2026 ratings in response and has appealed the decision. Reporting in June 2026 described CMS recalculating ratings again, adding further volatility to a program plans must budget against years in advance.
What this means for the field
Three honest implications:
- The ratings are less stable than they appear. A number that determines billions in payment has been recalculated more than once under litigation pressure.
- Plans now litigate as a strategy. With this much money attached and precedent established, challenges are likely to continue.
- Procedural discipline matters. The clearest lesson for CMS, and for any agency, is that shortcuts in how a requirement is adopted can undo it entirely, regardless of its merits.
For anyone reading MA quality data, the practical caution is to check whether the ratings in front of you are the original or a recalculated set, and to hold them a little more loosely than a settled measurement would deserve.
Key takeaways
- Numerous insurers have sued CMS over Star Ratings, with individual disputes reaching $32 million and $115 million.
- A May 2026 ruling threw out twenty measures from the 2026 ratings, half for unauthorized data sources and half for skipping notice-and-comment rulemaking.
- CMS recalculated the ratings and is appealing; treat MA quality ratings as less settled than their precision suggests.
Sources
Check your understanding
On what grounds did a federal court invalidate measures used in the 2026 Star Ratings?
In the Clover litigation a Georgia federal court threw out twenty measures: ten based on unauthorized data sources, and ten adopted without notice-and-comment rulemaking. Procedure, not just substance, decided the case.