CMS-HCC V28: What risk adjustment teams need to know

CMS-HCC Model V28 is the newest version of the risk adjustment model CMS uses to calculate RAF scores for Medicare Advantage members, and it's being phased in on a blended basis with the older V24 model. V28 restructures which ICD-10 diagnosis codes map to which HCCs — consolidating some categories, removing others, and tightening the clinical criteria for several conditions that were considered easy RAF contributors under V24. The net effect for most plans and provider groups is a lower average RAF score per member unless coding practices adapt to the new mappings.

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Why the mapping changes matter more than the model version

It's tempting to treat V28 as a compliance checkbox — confirm your software is "V28-ready" and move on. But the real work is in the mapping changes themselves. Diagnoses that reliably triggered an HCC under V24 — certain diabetes complications, vascular disease codes, and some mental health conditions — either map to a different, lower-weighted HCC under V28, or don't map to any HCC at all. Coding teams and CDI programs that don't retrain around the new mappings will keep coding the same way and simply capture less revenue for the same clinical acuity, without any visibility into why.

Where risk-bearing providers and payers are most exposed

Three areas tend to see the biggest swings under V28:

• Diabetes with complications — several complication codes that mapped to distinct, higher-weighted HCCs under V24 are consolidated under V28, reducing the RAF contribution unless the full complexity of the patient's diabetes is captured across multiple qualifying diagnoses.
• Vascular disease — some peripheral vascular and circulatory codes see reduced or restructured HCC mapping, which can understate risk for patients whose charts were previously coded to older category definitions.
• Behavioral health — mapping changes to certain mood and psychotic disorder codes shift RAF weight in ways that catch provider groups and plans off guard if coding templates haven't been updated.

What this means for RAF accuracy

Because V28 is being phased in through a blend with V24 (CMS is stepping up the V28 weighting each payment year during the transition), a plan or provider group's blended RAF score reflects a mix of both models simultaneously. That makes trend analysis harder — a RAF dip could reflect genuinely healthier patients, coding practices that haven't adapted to V28, or a shift in the blend percentage. Teams that can't separate those causes risk either under-investing in coding improvement (assuming the dip is just "the model") or over-reacting to a transition effect that will resolve on its own.

How to adapt coding and CDI programs

The organizations managing this transition best are treating it as a documentation-completeness problem, not a software update. That means:

• Auditing which HCCs historical coding volume concentrated in, and checking each against the new V28 mapping to see where RAF weight shifted
• Updating CDI queries and coding templates to prompt for the specific documentation detail V28 requires to qualify a diagnosis for its (often narrower) HCC category
• Reviewing retrospective chart review workflows to make sure they're evaluating against V28 criteria, not legacy V24 logic

How Charta helps

Charta's risk adjustment platform applies current CMS-HCC mapping logic — including V28 — automatically across every chart it reviews, so coding teams don't have to manually retrain judgment calls that the model itself has already changed. Combined with RADV-ready documentation validation, that means providers and payers capture every HCC the current model actually supports, rather than coding to a mental model that's already out of date.

Learn more

To learn more about Charta's risk adjustment solutions, request a demo from a member of our team today.