What is HCC Coding?
HCC stands for Hierarchical Condition Category. HCC coding is a risk adjustment methodology used by the Centers for Medicare & Medicaid Services (CMS) to calculate how much Medicare Advantage plans are paid for each enrollee.
In plain terms — HCC coding tells Medicare how sick your patients are. Sicker patients cost more to treat, so Medicare pays more for them. HCC coding is how that calculation happens.
Every ICD-10-CM diagnosis code maps to one of approximately 86 HCC categories under the current CMS-HCC Model V28. Each HCC category carries a Risk Adjustment Factor (RAF) score that determines its payment weight. The higher the RAF score, the more Medicare pays for that patient.
Key Insight: HCC coding is not just a billing function — it directly determines Medicare Advantage plan revenue. Accurate and complete HCC coding can mean hundreds of thousands of dollars in recovered or at-risk revenue for a health plan or provider organization.
How HCC Coding Works
The HCC risk adjustment process works like this:
- Diagnosis codes are submitted on Medicare Advantage claims throughout the year
- CMS maps each ICD-10 code to an HCC category using the CMS-HCC model
- HCC categories are assigned RAF scores — each category has a specific numeric weight
- All RAF scores are added together along with demographic factors (age, sex, Medicaid status, disability status)
- The total RAF score determines the monthly capitated payment Medicare makes to the plan for that enrollee
The average Medicare Advantage enrollee has a RAF score around 1.0. A healthier patient might score 0.5 while a patient with multiple chronic conditions could score 3.0 or higher.
HCC Coding vs Regular ICD-10 Coding
Regular ICD-10 coding focuses on accuracy for claims processing and reimbursement for individual encounters. HCC coding has a broader focus:
- Prospective — HCC diagnoses from one year predict and determine payment for the following year
- Chronic conditions — HCC coding focuses on ongoing chronic conditions, not just acute episodes
- Annual recapture — HCC conditions must be documented and coded every year to maintain the risk score
- Specificity matters — more specific codes often map to higher-weighted HCC categories
Understanding RAF Scores
The Risk Adjustment Factor (RAF) score is the numeric value assigned to each HCC category. RAF scores represent the relative cost of caring for a patient with that condition compared to an average Medicare beneficiary.
A RAF score of 1.0 means average cost. A score of 2.0 means the patient is expected to cost twice as much as average. A score of 0.5 means half the average cost.
| RAF Score Range | Severity | Example Conditions |
|---|---|---|
| 1.0+ | High impact | Respirator dependence (1.974), Metastatic cancer (2.659), Quadriplegia (1.233) |
| 0.2 – 0.49 | Moderate impact | CHF (0.323), COPD (0.326), CKD Stage 5 (0.289), Schizophrenia (0.444) |
| < 0.2 | Lower impact | Diabetes without complications (0.105), Angina (0.096) |
Patient RAF scores are additive — a patient with diabetes (0.105), CHF (0.323), and CKD Stage 4 (0.118) would have a combined condition RAF of 0.546 before demographic factors are added.
CMS-HCC Model V28 (2026)
CMS updates the HCC model periodically to reflect changes in medical practice and coding. CMS-HCC Model V28 is the current model effective for payment year 2026.
Key changes in V28 compared to prior models:
- Reorganized HCC categories to better reflect clinical groupings
- Updated RAF scores based on more recent Medicare claims data
- Refined diabetes HCC hierarchy — more specific diabetes codes now map to different categories
- New HCC categories added for conditions previously not captured
- Some codes that previously mapped to HCCs were removed from the model
Important: CMS is transitioning from the older V24 model to V28 over three years (2024–2026). For 2026, V28 is fully in effect. Coders should verify that their HCC references use V28 data, not the older V24 mappings.
Most Common HCC Categories
These are the HCC categories coders encounter most frequently in Medicare Advantage populations:
High-Frequency HCC Categories — CMS-HCC Model V28
| HCC | Category | RAF Score | Common Codes |
|---|---|---|---|
| HCC17 | Diabetes without Complication | 0.105 | E11.9, E10.9 |
| HCC18 | Diabetes with Chronic Complications | 0.302 | E11.21, E11.40, E11.51 |
| HCC85 | Congestive Heart Failure | 0.323 | I50.9, I50.20–I50.43 |
| HCC111 | COPD | 0.326 | J44.0, J44.1, J44.9 |
| HCC137 | CKD Stages 3–4 | 0.118 | N18.3, N18.4 |
| HCC136 | CKD Stage 5 / ESRD | 0.289 | N18.5, N18.6 |
| HCC96 | Specified Heart Arrhythmias | 0.175 | I48.0, I48.11, I48.91 |
| HCC58 | Major Depressive/Bipolar Disorders | 0.309 | F32.9, F33.0, F31.9 |
Why HCC Coding Matters
For Medicare Advantage Plans
Medicare Advantage plans receive capitated payments from CMS based on the RAF scores of their enrolled population. Incomplete or inaccurate HCC coding directly reduces plan revenue. A plan with 10,000 members and an average RAF score of 0.1 below benchmark could be leaving millions of dollars in underpayment on the table annually.
For Providers and Health Systems
Value-based contracts increasingly tie provider reimbursement to risk-adjusted quality metrics. Accurate HCC coding ensures providers are fairly compensated for the complexity of their patient population and not penalized for caring for sicker patients.
For Patients
When chronic conditions are properly coded and captured, care management programs can identify high-risk patients, coordinate care proactively, and potentially prevent costly hospitalizations and complications.
HCC Coding Best Practices
- Code chronic conditions every encounter — HCC conditions must be recaptured annually. A diabetic patient seen for an unrelated issue should still have their diabetes coded if it was assessed or managed.
- Use the most specific code available — E11.40 (diabetic neuropathy) maps to a higher HCC than E11.9 (diabetes without complications) when clinically accurate.
- Document supports diagnosis — HCC coding is audited by CMS. Every coded condition must be supported by current clinical documentation.
- Annual wellness visits are key — AWV encounters are an ideal opportunity to review and capture all active chronic conditions for the year.
- Know your hierarchies — HCC categories are hierarchical. More severe manifestations of a condition replace less severe ones — you don't code both.
- Verify V28 mappings — Some codes that mapped to HCCs in V24 do not map in V28. Always verify against the current model year.
Audit Risk: CMS conducts Risk Adjustment Data Validation (RADV) audits to verify HCC coding accuracy. Overcoding — submitting HCC diagnoses not supported by medical records — carries significant compliance risk including repayment obligations and potential False Claims Act liability.
Free HCC Lookup Tool
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