The blend is gone. Full V28 is your payment model now.
CMS phased the 2024 CMS-HCC risk adjustment model (V28) in over three payment years to soften the transition off V24. Payment year 2024 paid on a 67 percent V24, 33 percent V28 blend. Payment year 2025 flipped to 33 percent V24, 67 percent V28. Payment year 2026 is 100 percent V28. There is no V24 component left in the payment calculation.
Full V28 is not a re-weighting alone. CMS restructured the model itself. The count of payment HCCs was reduced, several conditions were remapped or constrained so they no longer map to a payment HCC, and the ICD-10 to HCC crosswalk changed underneath codes that practices have billed for years. The net effect on a book that has not recalibrated is RAF compression: the same documented population produces a lower risk score than it did under the blend, and lower than it did under V24.
The categories that moved hardest are the ones many primary care panels lean on. Practices that rebuilt their PMPM and fee-schedule models against the 2025 blend are still under-modeling the downside, because the 2025 blend still carried a third of the old V24 weight. Payment year 2026 removes that cushion. The fix is not coding harder. It is documentation specificity at the chart level plus a V28 crosswalk audit of the most-used ICD-10 codes against their current category mapping.
Primary source: CMS Risk Adjustment.