ICD-10 to HCC Mapping Updates for 2026: Impact on Risk Adjustment

FY2026 ICD-10-CM Overview

Understanding ICD-10 to HCC mapping is fundamental to accurate risk adjustment coding. The FY2026 ICD-10-CM update, effective October 1, 2025, introduced approximately 390 new diagnosis codes, revised 28 existing codes, and deleted 45 codes from the classification system. While the total code set now exceeds 73,000 codes, the subset that matters most for risk adjustment is the approximately 7,770 codes that map to HCCs under CMS-HCC V28.

Every annual update creates a ripple effect through risk adjustment operations. New codes may open additional pathways to HCC capture. Deleted codes eliminate pathways that coders relied on in prior years. Revised codes may change the specificity requirements or clinical definitions that determine whether a condition qualifies for HCC mapping. For organizations managing RAF scores across thousands of members, tracking these changes is not optional — it is a core operational requirement.

Key Code Changes Affecting HCCs

Not all 390 new codes affect risk adjustment equally. The changes that matter most are those that alter ICD-10-to-HCC mapping — creating new capture pathways, eliminating existing ones, or changing the specificity required to trigger an HCC.

• Metabolic Conditions: FY2026 introduced expanded specificity codes for diabetes complications, obesity classifications, and metabolic syndrome. Several new diabetes codes map directly to existing HCCs within the V28 diabetes disease family, providing coders with more precise options that match clinical documentation.
• Cardiovascular Updates: New codes for heart failure subtypes, peripheral vascular disease stages, and cerebrovascular conditions added granularity to cardiovascular HCC mapping. These codes enable more accurate severity differentiation, though under V28 constraining, the RAF coefficient remains identical within disease families.
• Neurological Conditions: Expanded codes for dementia subtypes, movement disorders, and neuropathies affect HCC mapping in the cognitive and neurological disease families. The additional specificity helps coders match documentation more precisely to the correct ICD-10 code.
• Substance Use Disorders: New codes for substance use disorder treatment status and severity align with the V28 expansion of substance use-related HCCs. These codes capture treatment context that was previously documented but not coded at sufficient specificity.
• Social Determinants of Health: While SDOH codes (Z55-Z65 range) do not map to HCCs, the expanded FY2026 SDOH codes support documentation completeness that influences coding accuracy and care coordination for risk-adjusted populations.

New Codes Added

The approximately 390 new codes span multiple clinical categories, but risk adjustment teams should prioritize understanding those that directly affect HCC mapping and RAF score calculation.

• Diabetes Specificity Codes: New codes distinguish between diabetes with specific microvascular and macrovascular complications at a granularity level that aligns with V28's diabetes HCC family. Coders now have more precise options for documenting diabetic retinopathy stages, nephropathy progression, and neuropathic subtypes.
• Heart Failure Classification: Expanded codes for heart failure with preserved ejection fraction (HFpEF), heart failure with reduced ejection fraction (HFrEF), and heart failure with mildly reduced ejection fraction (HFmrEF) provide clinical specificity that maps to cardiovascular HCCs under V28.
• Chronic Kidney Disease Staging: New codes add specificity for CKD stages with associated conditions, enabling more accurate capture of the renal disease HCC family. These codes are particularly important for dual diabetes-CKD populations where both disease families intersect.
• Cognitive Impairment Codes: New codes for mild cognitive impairment subtypes and dementia behavioral variants create additional pathways to neurological HCCs. These codes address a documentation gap where cognitive conditions were often coded at insufficient specificity to trigger HCC mapping.
• Chronic Pain Classifications: While chronic pain codes have limited direct HCC impact, new specificity options help document the clinical complexity of patients whose pain conditions complicate management of HCC-mapped chronic diseases.

Codes Removed or Revised

Deleted and revised codes represent the highest operational risk in any annual update. Coders who continue using deleted codes will generate claim rejections, and revised codes may change the clinical criteria for HCC qualification.

• Consolidated Codes: Several deleted codes were merged into broader or more specific replacement codes. For each deleted code, identify the replacement code and verify that the replacement still maps to the same HCC. Do not assume a one-to-one mapping — some consolidations result in codes that map to different HCCs or no HCC at all.
• Reclassified Conditions: Revised codes that changed clinical definitions may alter which conditions qualify for HCC capture. Review each revision against V28 mapping tables to confirm continued HCC eligibility.
• Obsolete Specificity Codes: Some codes were deleted because the condition was split into multiple more specific codes. Coders must transition to the new specific codes — using the parent or unspecified code instead will typically lose HCC mapping eligibility under V28.
• EHR Code Set Impact: Deleted codes remaining in EHR problem lists and diagnosis pick lists will cause documentation errors. EHR systems must be updated to remove or flag deleted codes and present replacement options to providers.
• Historical Claims Mapping: Retrospective reviews of charts documented before October 1, 2025, should use the code set effective at the date of service. Claims submitted for dates of service on or after October 1 must use FY2026 codes exclusively — using the prior-year code for the same condition is a rejection risk.

Impact on Risk Adjustment Revenue

The revenue impact of annual ICD-10 updates is often underestimated because the changes appear incremental. In practice, even small mapping changes can compound across large populations to produce material revenue effects.

• New Capture Opportunities: New codes that map to existing HCCs create revenue opportunities for conditions that were previously documented but coded at a level that did not trigger HCC mapping. Organizations that identify and train on these new pathways capture incremental RAF value.
• Lost Capture Pathways: Deleted codes that previously mapped to HCCs represent immediate revenue risk. If coders do not transition to the correct replacement code, conditions that were captured in prior years will silently drop from RAF calculations. For a 50,000-member plan, even 1% of members affected by a mapping loss can translate to hundreds of thousands of dollars in annual revenue impact.
• Documentation-Driven Specificity: Many new codes require higher documentation specificity than their predecessors. If provider documentation does not match the new specificity requirements, coders cannot select the more precise code — resulting in either an unspecified code that does not map to an HCC or a less specific code with a different mapping.
• RADV Implications: Using newly effective codes for conditions that were not previously documented at the required specificity level creates audit risk. The clinical documentation must support the level of specificity coded, regardless of whether the code is new or established.
• Cumulative Effect: Annual ICD-10 updates compound. Organizations that skip a year of update implementation carry forward both the current year's mapping gaps and the prior year's unaddressed changes. Within two years, the cumulative impact can exceed a 3-5% RAF accuracy degradation.

Updating Your Coding Workflows

Preparing for annual ICD-10 updates requires coordinated action across coding teams, clinical documentation, technology systems, and provider education. Here is a systematic approach to managing the transition.

• 60-Day Pre-Implementation Review: Begin reviewing new, deleted, and revised codes at least 60 days before October 1. Prioritize codes that affect HCC-mapped conditions, cross-reference against V28 mapping tables, and identify the highest-revenue-impact changes for your specific population.
• EHR and Coding Tool Updates: Coordinate with IT to update EHR diagnosis code sets, coding tool reference tables, and claims validation systems. Deleted codes should be flagged or removed from active pick lists, and new codes should be added with HCC mapping indicators.
• Targeted Coder Education: Conduct focused training sessions on the specific code changes that affect HCC coding accuracy for your population. Generic ICD-10 update training is insufficient — coders need to understand the RAF implications of each change.
• Provider Documentation Guidance: For new codes requiring higher specificity, communicate documentation requirements to providers before the effective date. Providers cannot document what they do not know is needed — proactive guidance prevents specificity gaps from forming.
• Post-Implementation Monitoring: Track claim rejection rates, HCC capture rates, and RAF score trends in the weeks following October 1. Spikes in rejections or drops in capture rates indicate code transition issues that need immediate attention.
• Mapping Table Validation: Verify that your internal ICD-10-to-HCC mapping tables match CMS-published crosswalks. Discrepancies between your mapping logic and CMS mapping create systematic capture errors that affect every member processed through the incorrect table.