What is CMS-HCC V28 Risk Adjustment Model? Definition, Formula, and Benchmark

CMS-HCC V28 is the risk-adjustment model CMS began phasing in for Medicare Advantage payment year 2024. It replaces the long-standing V24 model via a three-year blended transition: 2024 pays at 67% V24 / 33% V28, 2025 at 33% V24 / 67% V28, and 2026 forward at 100% V28.

V28 introduced material structural changes. Approximately 2,294 ICD-10-CM diagnoses that mapped to an HCC in V24 no longer map to any category in V28 — these are often referred to as "delisted" conditions. Coefficient values were rebalanced based on updated FFS cost data, with some chronic categories (diabetes without complications, certain vascular conditions) receiving lower coefficients and others (severe psychiatric illness, multiple renal failure subtypes) receiving higher coefficients. The overall effect for most plans is a reduction in average RAF of 2% to 7% depending on membership mix.

CMS justified V28 as a recalibration to current clinical practice and cost patterns. Industry responses have been mixed: plans with heavy chronic-condition documentation generally see less impact, while plans that relied on high-volume low-coefficient chronic codes (diabetes without complications is a frequent example) see larger RAF reductions. AHIP and individual plans have argued that V28 effectively compounds the coding intensity adjustment, further compressing MA economics.

Operationally V28 drives several changes in risk-adjustment programs. Chart review targeting must be re-prioritized toward conditions that remain high-coefficient in V28 (for example, specific diabetes complications coded to the subtype level, CKD stages 4–5, dementia with behavioral disturbance). Provider documentation training must emphasize the specificity V28 now requires — generic diabetes documentation that coded to 250.00 equivalents in V24 no longer carries the same weight when mapped into V28's restructured diabetes tree. Prospective coding suspect-condition lists have been rebuilt by vendors and internal teams to reflect V28 mappings.

CMS has published an official ICD-10-to-HCC mapping table for V28 that replaces the V24 crosswalk. Risk-adjustment vendors release updated software each Q4 to support the coming payment year's blend. Provider groups receiving risk-adjustment feedback reports from payers should confirm the report reflects the correct blended model for the payment year under review.

RADV audit methodology is agnostic to model version — auditors validate documentation against reported HCCs regardless of whether the HCC is under V24 or V28 coefficients. However, post-2024 audit findings implicitly reflect whether the reported HCCs are still relevant under V28; a plan that continued to submit delisted conditions faces no V28 recoupment (the payment was already zero) but faces compliance exposure if the condition was also unsupported.