V28 HCC Model Changes 2026: What Every Risk Adjustment Coder Needs to Know

Why V28 Matters in 2026

FY2026 marks the final year of the CMS-HCC V28 phase-in. Starting January 1, 2026, Medicare Advantage organizations are reimbursed using a blended model: 67% V28 and 33% V24. By 2027, V28 will be 100% of the risk adjustment calculation. This makes 2026 the last year where V24 HCC categories still carry partial weight — and the most critical year for coders to fully understand both models.

The CMS-HCC V28 model was finalized in the 2024 Rate Announcement (CMS-2024-0016) and represents the largest overhaul to the HCC risk adjustment framework since V24 was introduced. The model reduces the total number of HCC categories from 86 (V24) to 115 (V28), but this is not a simple expansion — many V24 categories were dropped, split, merged, or reclassified entirely.

Key Structural Changes in V28

Dropped HCC Categories

Several V24 HCCs were eliminated in V28. Coders who memorized V24 mappings must now verify every code against V28 tables. Notable drops include:

New Severity Tiers

V28 introduces severity tiers for several condition groups that V24 treated as single categories. Diabetes is the most impactful example:

Under V24, many of these mapped to a single HCC 18 (Diabetes with Chronic Complications) or HCC 19 (Diabetes without Complication). The V28 model requires coders to be far more specific about the type and severity of diabetic complications.

Heart Failure Reclassification

Heart failure categories were restructured to better reflect clinical severity:

Coders must now distinguish between systolic, diastolic, and combined heart failure, and between acute and chronic presentations, because the ICD-10 code determines which V28 HCC the patient falls into.

RAF Weight Shifts

The redistribution of RAF weights in V28 changes the financial value of every HCC capture. Some conditions gained significant value while others lost it:

Conditions That Gained Value

Conditions That Lost Value

What Coders Must Do to Adapt

1. Verify Every HCC Mapping Against V28 Tables

Do not rely on V24 muscle memory. Use a tool like the HCC Buddy encoder that shows both V24 and V28 mappings side-by-side for every ICD-10 code lookup. This eliminates the risk of assuming a code still maps to an HCC when it no longer does.

2. Prioritize Specificity in Documentation

V28 rewards specificity. A diagnosis of "heart failure" without further specification may map to HCC 226 (low severity, RAF 0.184), while "acute on chronic systolic heart failure" maps to HCC 224 (high severity, RAF 0.461). The difference in RAF value is 2.5x — driven entirely by how specifically the condition is documented and coded.

3. Learn the New Hierarchy Rules

V28 hierarchy trumping rules differ from V24. For example, V28 HCC 224 (Heart Failure, High Severity) trumps HCC 225 and HCC 226 — you cannot capture both a high-severity and low-severity heart failure HCC for the same patient. Understanding which HCCs trump others prevents wasted coding effort on conditions that will be zeroed out.

4. Track the Phase-In Calendar

For organizations doing prospective coding or chart reviews during 2026, both models still matter. Coders should be documenting to maximize capture under both V24 and V28 where possible.

CMS-HCC V28 Coding Reference

The ICD-10 to HCC mapping tool in HCC Buddy shows V24 and V28 HCC categories, RAF weights, and hierarchy rules for every billable ICD-10-CM code. The RAF Calculator lets you model patient RAF scores under both V24 and V28 to see the financial impact of each captured HCC.

For the complete list of V28 HCC categories and their RAF weights, see the CMS Risk Adjustment Model documentation at cms.gov.