What is ICD-10 code T31.99?

T31.99 is the ICD-10-CM diagnosis code for Burns involving 90% or more of body surface with 90% or more third degree burns. Catastrophic burns covering 90% or more of the body with 90% or more being third-degree burns affecting virtually the entire body surface. T31.99 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. T31.99 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. T31.99 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. T31.99 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 T31.99 map to under V28?

T31.99 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 T31.99: Burns involving 90% or more

T31.99 maps to CMS-HCC V28 385. A source-labeled RAF reference is available. Documentation must support MEAT. MEAT criteria · RAF Calculator · free HCC coding tools

ICD-10-CM Code View

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Code lookupT31.99Effective 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)

T31.99

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

Burns involving 90% or more of body surface with 90% or more third degree burns

Catastrophic burns covering 90% or more of the body with 90% or more being third-degree burns affecting virtually the entire body surface.

Buddy Insight

Burns involving 90% or more of body surface area with 90% or more third-degree burns represent the maximum possible catastrophic thermal injury with survival virtually impossible.

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

T31Burns classified according to extent of body surface involved

T31.9Burns involving 90% or more of body surface

T31.99Burns involving 90% or more of body surface with 90% or more third degree burns

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for T31.99 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for T31.99 in this effective period.

Related Child Codes

Official

T31.90Burns involving 90% or more of body surface with 0% to 9% third degree burns

T31.91Burns involving 90% or more of body surface with 10-19% third degree burns

T31.92Burns involving 90% or more of body surface with 20-29% third degree burns

T31.93Burns involving 90% or more of body surface with 30-39% third degree burns

T31.94Burns involving 90% or more of body surface with 40-49% third degree burns

Includes

Official

ICD-10-CM does not list Includes notes for T31.99 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for T31.99 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for T31.99 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for T31.99 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for T31.99 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Documentation of 90% or greater total body surface area involvement

Clear documentation that 90% or more of body surface has third-degree burns

Burn specialist assessment confirming maximum severity injury pattern

Evidence of extraordinary life support measures if attempted

MEAT Support

HCC Buddy guidance

Documentation of 90% or greater total body surface area involvement

Clear documentation that 90% or more of body surface has third-degree burns

Burn specialist assessment confirming maximum severity injury pattern

Evidence of extraordinary life support measures if attempted

Audit Caution

HCC Buddy guidance

Extreme difficulty in accurate assessment of such total body involvement

Not recognizing this as essentially universally fatal injury pattern

Failing to document appropriate goals of care discussions

Inadequate recognition of the comfort care needs for such injuries

Common Mistakes

HCC Buddy guidance

T31.98 — Burns 90%+ TBSA with 80-89% third degree (slightly less third-degree)

T31.97 — Burns 90%+ TBSA with 70-79% third degree (much less third-degree)

T31.89 — Burns 80-89% TBSA with 80-89% third degree (smaller total area)

T32.99 — Corrosions 90%+ TBSA with 90%+ third degree (chemical cause)

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 T31.99 an HCC code?

Yes. T31.99 (Burns involving 90% or more of body surface with 90% or more third degree burns) 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: T31.99 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: T31.99
Description: Burns involving 90% or more of body surface with 90% or more third degree burns
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 T31.99 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT Criteria for T31.99

For T31.99 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 T31.99 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

T31.99 is the ICD-10-CM diagnosis code for burns involving 90% or more of body surface with 90% or more third degree burns. Catastrophic burns covering 90% or more of the body with 90% or more being third-degree burns affecting virtually the entire body surface. T31.99 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, T31.99 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 T31.99; use the applicable model and payment year when reviewing the V28 mapping. 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. 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.

These are typically non-survivable injuries; ensure documentation reflects clinical reality and treatment decisions. Because T31.99 maps to an HCC category, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) before the diagnosis is used for risk adjustment. 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 T31.99 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•These are typically non-survivable injuries; ensure documentation reflects clinical reality and treatment decisions
•Include codes for shock, organ failure, and other life-threatening complications

Clinical Significance

Burns involving 90% or more of body surface area with 90% or more third-degree burns represent the maximum possible catastrophic thermal injury with survival virtually impossible. This represents complete or near-complete skin destruction across the entire body surface, typically incompatible with life and requiring immediate consideration of comfort care measures alongside any life-sustaining interventions.