What is ICD-10 code T32.42?

T32.42 is the ICD-10-CM diagnosis code for Corrosions involving 40-49% of body surface with 20-29% third degree corrosion. Chemical burn affecting 40-49% of the body surface, with the most severe burns (third degree) covering 20-29% of the affected area. T32.42 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. T32.42 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. T32.42 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. T32.42 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 T32.42 map to under V28?

T32.42 maps to CMS-HCC V28 HCC 385 (Severe Skin Burn or Condition). The category numbers, labels, and conditions come from the CMS-HCC V28 model file for payment year 2026.

2026 ICD-10-CM T32.42: Corrosions involving 40-49%

T32.42 maps to CMS-HCC V28 385. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC Buddy coding tools

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Code lookupT32.42

Effective 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)

T32.42

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

Corrosions involving 40-49% of body surface with 20-29% third degree corrosion

Chemical burn affecting 40-49% of the body surface, with the most severe burns (third degree) covering 20-29% of the affected area.

Buddy Insight

Overview Risk Models Code Book Documentation Audit Notes Edition comparison

CMS-HCC V28

Mapped

HCC 385

Severe Skin Burn or Condition

Code-level coefficient reference

CMS-HCC V24

Historical

Not used for standard CY2026 Medicare Advantage payment. Select a historical period to review V24.

Not used for CY2026 payment

ACA/HHS

Mapped

HCC 218

HHS-HCC 218 adult, RAF varies...

Code-level coefficient reference

ESRD/PACE

Mapped

HCC 162

Severe Skin Burn or Condition

Code-level coefficient reference

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 T32.4Corrosions involving 40-49% of body surface T32.42Corrosions involving 40-49% of body surface with 20-29% third degree corrosion

Inclusion Terms

Official

No inclusion terms are included in this display for T32.42. Check the code and parent instructions in the Code Book.

Excludes 2

Official

birth trauma (P10-P15)Inherited from S00-T88
obstetric trauma (O70-O71)Inherited from S00-T88

Related Codes

Official

T32.40Corrosions involving 40-49% of body surface with 0% to 9% third degree corrosion T32.41Corrosions involving 40-49% of body surface with 10-19% third degree corrosion T32.43Corrosions involving 40-49% of body surface with 30-39% third degree corrosion T32.44Corrosions involving 40-49% of body surface with 40-49% third degree corrosion

Includes

Official

No Includes notes are included in this display for T32.42. Check the code and parent instructions in the Code Book.

Excludes 1

Official

No Excludes 1 notes are included in this display for T32.42. Check the code and parent instructions in the Code Book.

Code First

Official

No Code First sequencing instructions are included in this display for T32.42. Check the code and parent instructions in the Code Book.

Use Additional

Official

code to identify any retained foreign body, if applicable (Z18.-)Inherited from S00-T88

Code Also

Official

No Code Also instructions are included in this display for T32.42. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance

Documentation of 40-49% total body surface area chemical corrosion

Clear documentation that 20-29% of affected area has third-degree corrosion

Identification of causative chemical agent and exposure details

Comprehensive emergency decontamination and neutralization documentation

MEAT Support

HCC Buddy guidance

Documentation of 40-49% total body surface area chemical corrosion

Clear documentation that 20-29% of affected area has third-degree corrosion

Identification of causative chemical agent and exposure details

Comprehensive emergency decontamination and neutralization documentation

Audit Caution

HCC Buddy guidance

Failing to distinguish chemical corrosion mechanisms from thermal burns

Not recognizing the critical care requirements for extensive chemical injuries

Inadequate documentation of chemical-specific protocols and monitoring

Missing the assessment of systemic toxicity from significant chemical exposure

Common Mistakes

HCC Buddy guidance

T31.42 — Thermal burns 40-49% TBSA with 20-29% third degree (thermal, not chemical)

T32.41 — Corrosions 40-49% TBSA with 10-19% third degree (less third-degree)

T32.43 — Corrosions 40-49% TBSA with 30-39% third degree (more third-degree)

T32.32 — Corrosions 30-39% TBSA with 20-29% third degree (smaller total area)

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 T32.42 an HCC code?

Yes. T32.42 (Corrosions involving 40-49% of body surface with 20-29% third degree corrosion) maps to HCC 385, Severe Skin Burn or Condition under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 1.291. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.

Coder answer: T32.42 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: T32.42
Description: Corrosions involving 40-49% of body surface with 20-29% third degree corrosion
HCC (V28): HCC 385 — Severe Skin Burn or Condition
RAF reference coefficient: 1.291
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 385, Severe Skin Burn or Condition

1.291

ESRDHCC 162, Severe Skin Burn or Condition

Not separately weighted

These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. 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 context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.

Work T32.42 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for T32.42

For T32.42, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

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

Coder workflow notes

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What This Code Means

T32.42 is the ICD-10-CM diagnosis code for corrosions involving 40-49% of body surface with 20-29% third degree corrosion. Chemical burn affecting 40-49% of the body surface, with the most severe burns (third degree) covering 20-29% of the affected area. T32.42 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, T32.42 maps to Severe Skin Burn or Condition (HCC 385) with a source-labeled community, non-dual, aged reference coefficient of 1.291. No V24 mapping is shown for T32.42; use the applicable model and payment year when reviewing the V28 mapping. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.

Ensure the third-degree percentage is documented separately from the total body surface area involved. For T32.42, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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, source-labeled coefficient references, and MEAT documentation criteria for T32.42 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Ensure the third-degree percentage is documented separately from the total body surface area involved
•These codes indicate moderate to severe corrosion injuries requiring specialized burn center care

Clinical Significance

Corrosions involving 40-49% of body surface area with 20-29% third-degree involvement represent critical chemical burn injury with extremely high mortality risk requiring immediate life-saving interventions. This extensive chemical exposure pattern involves significant full-thickness tissue destruction alongside potential systemic toxicity, demanding specialized chemical burn center care with comprehensive toxicological support and intensive surgical intervention.

Documentation Requirements

✓Documentation of 40-49% total body surface area chemical corrosion
✓Clear documentation that 20-29% of affected area has third-degree corrosion
✓Identification of causative chemical agent and exposure details
✓Comprehensive emergency decontamination and neutralization documentation
✓Assessment of ongoing chemical activity and progressive tissue damage
✓Evidence of immediate chemical burn center admission
✓Documentation of systemic toxicity monitoring and specific antidotal therapy
✓Surgical planning for extensive debridement and reconstruction

Commonly Confused Codes

•T31.42: Thermal burns 40-49% TBSA with 20-29% third degree (thermal, not chemical)
•T32.41: Corrosions 40-49% TBSA with 10-19% third degree (less third-degree)
•T32.43: Corrosions 40-49% TBSA with 30-39% third degree (more third-degree)
•T32.32: Corrosions 30-39% TBSA with 20-29% third degree (smaller total area)
•T32.52: Corrosions 50-59% TBSA with 20-29% third degree (larger total area)