HCC and RAF: How HCC Coding Drives the RAF Score
If you understand the relationship between HCC and RAF, you understand risk-adjusted payment. This guide explains what HCCs are, how they map from ICD-10 codes, how the hierarchy works, and how HCCs translate into a RAF score.
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Key data points
- The legacy V24 payment model uses roughly 86 payment HCCs; V28 expands and renumbers to about 115 HCCs.
- V28 removes thousands of ICD-10 codes from risk adjustment relative to V24.
- Within an HCC disease family, only the single highest-severity category counts toward the RAF score (the hierarchy / trumping rule).
Source: CMS CY2024 Medicare Advantage and Part D Rate Announcement.
Quantified: the same diagnoses can swing materially in RAF and Medicare Advantage payment purely from how V24 vs V28 maps the HCCs. A full dollar example is worked end to end in what a RAF score is; model your own with the V24 vs V28 tool.
What Is an HCC?
An HCC (Hierarchical Condition Category) is a clinically related grouping of ICD-10-CM diagnosis codes used by the CMS-HCC risk adjustment model. Thousands of individual diagnosis codes roll up into a much smaller set of categories that each represent a chronic or serious condition with a predictable cost impact — for example, "diabetes with chronic complications" or "congestive heart failure." Each HCC has an associated risk coefficient.
From ICD-10 to HCC to RAF
The chain is straightforward once you see it laid out:
| Step | What happens |
|---|---|
| 1. Documentation | The provider documents a condition in the medical record (meeting MEAT criteria). |
| 2. ICD-10 coding | The condition is coded to a specific ICD-10-CM diagnosis code. |
| 3. Crosswalk | The ICD-10 to HCC crosswalk maps that code to an HCC. |
| 4. Coefficient | The HCC contributes its coefficient (risk weight) to the model. |
| 5. RAF score | HCC coefficients + demographics + interactions sum to the patient's RAF score. |
This is why HCC coding accuracy is the single biggest lever on RAF accuracy: a condition that is treated but not documented and coded never reaches step 3, so it never affects the RAF score.
How the HCC Hierarchy Works
The "hierarchical" part of HCC is essential. Within a clinical disease family, conditions are ranked by severity, and only the single most severe HCC counts toward the RAF score. A more severe category "trumps" the less severe ones in the same family, so the same underlying disease is not paid for multiple times. For example, if a patient has both a lower-severity and a higher-severity diabetes HCC documented, only the higher-severity HCC's coefficient applies.
What Is an HCC RAF Score?
HCC vs RAF in one line: an HCC is a clinical category of diagnoses; the RAF score is the single number those categories (plus demographics) add up to.
| Aspect | HCC | RAF score |
|---|---|---|
| What it is | Clinical grouping of related ICD-10 codes | Final numeric risk / payment factor |
| Role | Building block | Aggregate result |
| Derived from | ICD-10-CM codes via the crosswalk | Sum of HCC + demographic + interaction coefficients |
| Baseline | — | 1.0 = average beneficiary |
| Used for | Categorizing disease burden | Risk-adjusting CMS payment |
| Resets | Annually (re-document) | Annually |
"HCC RAF score" generally refers to the disease-driven portion of the RAF score — the sum of the patient's HCC coefficients — combined with demographic factors to produce the total RAF. In practice the terms are used together because HCCs are the mechanism by which clinical complexity becomes a payable risk number. To see the full calculation end to end, read what a RAF score is and how it is calculated, or compute one directly with the RAF Score Calculator.
HCC and RAF Scores: The CMS HCC RAF Relationship
"HCC and RAF" are almost always discussed together because they are two ends of the same pipeline. In the CMS HCC RAF model, RAF HCC coding — documenting a chronic condition and coding it to the ICD-10 code that maps to the correct HCC — is what converts clinical complexity into a payable risk number. Get the HCC coding right and the RAF score reflects reality; miss it and the RAF score (and the payment it drives) understates the patient.
Put simply: HCCs are the categories, the RAF score is the total, and CMS HCC RAF coding is the process that connects them every calendar year. This is why risk-adjustment teams track HCC capture rate as the leading indicator of RAF accuracy, and why the relationship matters most in Medicare Advantage risk adjustment.
RAF measures predicted cost and complexity — it is distinct from quality measurement. For how risk adjustment compares with quality scoring, see RAF vs HEDIS.
HCC Counts Differ by Model Version
The set of HCCs is not fixed: the V24 and V28 models group and weight conditions differently, so the same diagnosis can map to a different HCC — or to none — depending on the model in force. The mechanism (ICD-10 → HCC → coefficient → RAF) is identical; only the mapping and weights change. The full V24-to-V28 transition, timeline, and financial impact are covered in the CMS-HCC V28 guide; the V24 vs V28 tool compares a specific patient.
Why HCC Documentation Matters
Because HCCs reset each calendar year, every chronic condition must be re-documented and re-coded annually to keep contributing to the RAF score. Gaps in HCC capture understate patient complexity and reduce risk-adjusted revenue for genuinely complex populations; unsupported HCCs create RADV-audit exposure. Accurate HCC coding — supported by the record — is the foundation of compliant value-based care.
Try the HCC RAF score calculator
Paste ICD-10 codes — this free HCC RAF calculator maps them to HCCs and returns the RAF score under V24 or V28.
Open the HCC RAF Score CalculatorFrequently Asked Questions
An HCC is a clinical grouping of related ICD-10 codes used by the CMS-HCC model. Each HCC carries a coefficient that contributes to the RAF score.
Within a disease family, only the single most severe HCC counts toward the RAF score; lower-severity related categories are trumped so a condition is not paid twice.
Each documented and coded HCC adds its coefficient to the RAF score, alongside demographic factors and interaction terms.
V24 uses roughly 86 payment HCCs; V28 expands and renumbers to about 115 HCCs while removing many codes from risk adjustment. See the HCC V28 guide.
An HCC is a clinical category of related ICD-10 diagnoses; the RAF score is the single number those categories plus demographics add up to. HCCs are the building blocks; the RAF score is the result CMS uses for payment.
Yes. The free HCC RAF score calculator accepts ICD-10 codes, maps them to HCCs, and returns the RAF score under the V24 or V28 model so you do not have to compute coefficients by hand.
Where HCC capture breaks
- A treated condition never coded to a mapping ICD-10 never becomes an HCC.
- Unspecified codes outside the crosswalk add no RAF weight.
- The hierarchy is misread — only the most severe HCC in a clinical family counts.
- V28 dropped many codes from risk adjustment; a V24-era code list silently under-captures.
General compliance guidance; confirm specifics against the current CMS Rate Announcement and your organization's policy.
This page is educational and does not constitute coding, billing, legal, or clinical advice. HCC structures and coefficients change by CMS-HCC model version and payment year; always confirm against the current CMS Rate Announcement and your organization's compliance guidance. CPT® is a registered trademark of the American Medical Association; HEDIS® is a registered trademark of the National Committee for Quality Assurance (NCQA). This page is independent and is not affiliated with, endorsed by, or sponsored by CMS, the AMA, or NCQA.