What is ICD-10 code T32.66?

T32.66 is the ICD-10-CM diagnosis code for Corrosions involving 60-69% of body surface with 60-69% third degree corrosion. It belongs to the ICD-10-CM chapter for injury, poisoning and certain other consequences of external causes (s00-t88). T32.66 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. T32.66 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. T32.66 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. T32.66 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Which HCC does T32.66 map to under V28?

T32.66 maps to CMS-HCC V28 385 (Severe Skin Burn or Condition). The category number and label come from the CMS-HCC V28 model file for payment year 2026.

What does T32.66 pay in RAF?

T32.66 carries a community, non-dual, aged (CNA) RAF weight of 1.291 under CMS-HCC V28 for payment year 2026. The weight comes from the CMS V28 relative-factor file, not a hand-typed table.

What is the V28 vs V24 difference for T32.66?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. For T32.66, V28 maps to Severe Skin Burn or Condition at RAF 1.291 while V24 mapped to Severe Skin Burn or Condition at RAF 0.224. Both models can still appear in legacy data and in payer-specific lookback periods.

What documentation supports T32.66?

This code indicates the most severe category within the 60-69% body surface range and requires immediate specialized burn care Always include the seventh character extension for proper documentation of care episode Because T32.66 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score. See the MEAT criteria checklist at /meat-criteria for what Monitor, Evaluate, Assess, or Treat looks like in a note. MEAT is generic documentation evidence, not a payer-specific rule.

2026 ICD-10-CM T32.66: Corrosions involving 60-69%

T32.66 maps to CMS-HCC V28 385 (RAF 1.291). Documentation must support MEAT. MEAT criteria · RAF calculator · HCC Buddy coding tools

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Code lookupT32.66Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Injury, poisoning and certain other consequences of external causes (S00-T88) / Burns and corrosions of multiple and unspecified body regions (T30-T32)

T32.66

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Corrosions involving 60-69% of body surface with 60-69% third degree corrosion

Chemical burn affecting 60-69% of the body surface with 60-69% deep tissue damage (third degree corrosion). This is a critical chemical injury where the majority of affected area involves full-thickness burns.

Buddy Insight

CMS-HCC V28

Mapped

HCC 385

Severe Skin Burn or Condition

RAF 1.291

CMS-HCC V24

Mapped

HCC 162

Severe Skin Burn or Condition

RAF 0.224

ACA/HHS

Mapped

HCC 218

HHS-HCC 218

Varies by metal level

ESRD/PACE

Mapped

HCC 162

Severe Skin Burn or Condition

RAF 0.155

RXHCC

N/A

—

Not risk-adjusted for this model/period.

Not mapped

Code Book Path

Official

T32Corrosions classified according to extent of body surface involved

T32.6Corrosions involving 60-69% of body surface

T32.66Corrosions involving 60-69% of body surface with 60-69% third degree corrosion

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for T32.66 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for T32.66 in this effective period.

Related Child Codes

Official

T32.60Corrosions involving 60-69% of body surface with 0% to 9% third degree corrosion

T32.61Corrosions involving 60-69% of body surface with 10-19% third degree corrosion

T32.62Corrosions involving 60-69% of body surface with 20-29% third degree corrosion

T32.63Corrosions involving 60-69% of body surface with 30-39% third degree corrosion

T32.64Corrosions involving 60-69% of body surface with 40-49% third degree corrosion

Includes

Official

ICD-10-CM does not list Includes notes for T32.66 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for T32.66 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for T32.66 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for T32.66 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for T32.66 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Total body surface area documentation (60-69%)

Third-degree burn percentage (60-69%)

Specific chemical agent and concentration

Time of exposure and contact duration

MEAT Support

HCC Buddy guidance

Total body surface area documentation (60-69%)

Third-degree burn percentage (60-69%)

Specific chemical agent and concentration

Time of exposure and contact duration

Audit Caution

HCC Buddy guidance

Confusing total BSA with third-degree percentages

Using burn codes instead of corrosion codes

Inadequate external cause code documentation

Errors in calculating extensive burn areas

Common Mistakes

HCC Buddy guidance

T32.65 — Has 50-59% third-degree involvement instead of 60-69%

T32.77 — Has 70-79% third-degree involvement instead of 60-69%

T32.56 — Involves 50-59% total BSA instead of 60-69%

T31.66 — Thermal burns, not chemical corrosions

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is T32.66 an HCC code?

Yes. T32.66 (Corrosions involving 60-69% of body surface with 60-69% third degree corrosion) maps to Severe Skin Burn or Condition under the CMS-HCC V28 risk adjustment model (and Severe Skin Burn or Condition under V24), with a community non-dual aged RAF of 1.291. It is billable for payment year 2026.

Coder answer: T32.66 is billable and maps to V28 HCC 385, Severe Skin Burn or Condition. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: T32.66
Description: Corrosions involving 60-69% of body surface with 60-69% third degree corrosion
HCC (V28): HCC 385 — Severe Skin Burn or Condition
RAF: 1.291
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 385, Severe Skin Burn or Condition

1.291

V24HCC 162, Severe Skin Burn or Condition

0.224

ESRDHCC 162, Severe Skin Burn or Condition

0.155

Each model's RAF is its CMS base weight for that model's standard population, so weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

Work T32.66 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for T32.66

For T32.66 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.

MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
EEvaluate: test results, medication response, or physical findings reviewed by the provider
AAssess: explicit mention in the assessment or plan with acknowledgment of status
TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed T32.66 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

T32.66 is the ICD-10-CM diagnosis code for corrosions involving 60-69% of body surface with 60-69% third degree corrosion. Chemical burn affecting 60-69% of the body surface with 60-69% deep tissue damage (third degree corrosion). This is a critical chemical injury where the majority of affected area involves full-thickness burns. T32.66 sits in the ICD-10-CM chapter for injury, poisoning and certain other consequences of external causes (s00-t88), within the section covering burns and corrosions of multiple and unspecified body regions (t30-t32).

Under the CMS-HCC V28 risk adjustment model, T32.66 maps to Severe Skin Burn or Condition (HCC 385) with a community, non-dual, aged base RAF weight of 1.291. Under the older V24 model, T32.66 mapped to the same category but with a base RAF weight of 0.224, V28 recalibrated weights across the entire model. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.

This code indicates the most severe category within the 60-69% body surface range and requires immediate specialized burn care. Because T32.66 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for T32.66 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•This code indicates the most severe category within the 60-69% body surface range and requires immediate specialized burn care
•Always include the seventh character extension for proper documentation of care episode

Clinical Significance

This represents critical chemical burns involving 60-69% of the body where the majority of affected area has full-thickness destruction (60-69% third-degree), indicating catastrophic injury with extremely high mortality risk. These patients require immediate burn center care with aggressive surgical intervention and face significant risk of death or severe permanent disability.