What Is CMS-HCC V28
CMS-HCC V28 is the current version of the Hierarchical Condition Category risk adjustment model used by CMS to calculate Medicare Advantage capitation payments. It replaced the legacy V24 model, transitioning from a blended phase-in (67/33 in 2024, 33/67 in 2025) to 100% V28 in 2026.
V28 represents a ground-up rebuild natively calibrated on ICD-10-CM data from 2017-2019, replacing V24's ICD-9 crosswalk foundation. The model includes 115 HCCs organized into 26 disease families, with approximately 7,770 ICD-10 codes mapped to condition categories.
Key Structural Changes
Constraining is the most significant change — related HCCs within the same disease family now carry identical coefficients regardless of severity. All diabetes HCCs (except pancreas transplant) share the same weight of approximately 0.166, a fundamental departure from V24 where more severe conditions earned higher coefficients.
ICD-10 Code Reduction: V28 maps 7,770 ICD-10 codes compared to V24's 9,797 — a net reduction of 2,027 codes. This eliminates many unspecified diagnosis codes, requiring greater coding specificity.
Expanded Categories: V28 increased the HCC count from 86 to 115, with expanded coverage of behavioral health conditions and new disease interaction factors.
Revenue Impact
CMS projected a 3.12% average reduction in MA risk scores under V28. Early industry data shows actual RAF score declines of 5-30% for plans maintaining identical patient populations, driven primarily by constraining and reduced ICD-10 mappings.
For a 50,000-member plan, a systematic 0.1 RAF score understatement translates to approximately $5.2M in unrealized annual revenue. Organizations that understand V28's mechanics and adapt their documentation and coding workflows accordingly will outperform those relying on legacy V24 assumptions.