Medicare Advantage Coding Guidelines

What are Medicare Advantage coding guidelines?

Reviewed by Jess P., CPC · Updated for CMS-HCC V28 and FY2026 ICD-10-CM

Medicare Advantage coding guidelines are the rules that govern how a risk-adjustment coder captures and validates diagnoses for a Medicare Advantage member. They sit on top of the ICD-10-CM code set rather than replacing it: the code set tells you which characters are valid for a condition, while the guidelines tell you when a diagnosis is supportable, what documentation a chart must contain, and how a specific payer expects the diagnosis to be reported. A coder who knows ICD-10-CM cold can still submit a code that fails a retrospective review because a payer’s guidance required documentation the chart did not have.

Coding guidelines vs the ICD-10-CM code set

The ICD-10-CM code set is the standardized diagnosis vocabulary maintained for the United States, updated annually (the FY2026 update applies from October 1, 2025). The Official Guidelines for Coding and Reporting that ship with it define how to sequence and assign those codes. Medicare Advantage coding guidelines are narrower and more operational: they tell a risk-adjustment coder which of those codes are eligible to map into a hierarchical condition category, what counts as acceptable provider documentation, and how a particular health plan wants the work performed and audited. In practice a coder reconciles three layers at once — the code set, the official coding guidelines, and the payer-specific guidance — and most denials live in that third layer.

Categories of payer guidance

Payer guidance for risk adjustment generally falls into three buckets:

• CMS risk-adjustment guidance. The model files, mapping tables, and program rules published by CMS that define the CMS-HCC model itself — which ICD-10-CM codes map to which HCCs, the RAF coefficients, and the documentation expectations CMS enforces through RADV audits.
• Plan-specific Documents of Understanding (DOUs). Formal agreements between a health plan and its contracted coding vendors that specify coding rules, acceptable documentation formats, quality thresholds, and compliance requirements for retrospective chart review.
• Local and plan policies. Plan-level coding policies, claim-edit rules, and condition-specificity requirements that can vary by line of business and document version, and that often go beyond the baseline ICD-10-CM guidance.

What changed for 2026

The defining shift for payment year 2026 is that the CMS-HCC V28 model is fully phased in at 100% of the risk score, with the older V24 model no longer blended in. That matters for guidelines work because V28 reorganized the HCC hierarchy and removed or remapped a number of conditions relative to V24, so guidance written against the older model can point coders at categories that no longer pay the way they used to. The prescription-drug side of risk adjustment, the RxHCC model, also continues to be updated by CMS on its own schedule. Coders verifying medicare advantage coding guidelines for 2026 should confirm each rule against the current model year rather than carrying forward last year’s assumptions. CMS publishes the authoritative model files, mapping tables, and program guidance on its Medicare Advantage Risk Adjustment page, which is the source of record for what the model covers in any given payment year.

Where guidelines bite during chart review

The reason payer guidance matters in day-to-day work is that a diagnosis can be perfectly valid in ICD-10-CM and still be unsupportable under the guidelines a coder is held to. A condition may need to be explicitly addressed in the encounter rather than carried forward from a problem list; the documentation may need to show that the provider evaluated, assessed, or treated it in the visit; and the supporting note may need to come from a face-to-face encounter within the data-collection period. Those requirements rarely live in the code set itself — they live in CMS program guidance and in each plan’s DOU. When a coder cannot find the relevant rule fast, the practical outcome is a code that gets removed on audit, which is exactly the loss risk-adjustment programs are trying to avoid.

HCC Buddy turns these documents into something a coder can query mid-session instead of reading end to end. Uploaded guideline PDFs are screened for Protected Health Information (PHI) before processing and any document containing PHI is rejected — HCC Buddy is built on a Zero PHI posture and does not store, log, or transmit patient-identifiable data. Your guidelines are stored encrypted and accessible only to your account.

How guideline search speeds up coding

Sources

• CMS — CMS-HCC risk-adjustment model files and mapping tables: cms.gov/medicare/health-plans/medicareadvtgspecratestats/risk-adjustors
• CMS — ICD-10-CM code set: cms.gov/medicare/coding-billing/icd-10-codes