ICD-10 code T31.74: 70–79% TBSA burns with 40–49% third-degree burns

Key takeaways

T31.74 is a billable ICD-10-CM code for burns covering 70-79% of total body surface area (TBSA). Within that, 40-49% of total body surface must be third degree.

Both percentages in the code title are direct shares of total body surface, never a ratio of the burned area.

The Rule of Nines is the standard adult TBSA estimation method, and the Lund-Browder chart is preferred for pediatric patients.

T31.74 is used as an additional code alongside site-specific T20-T25 burn codes under ICD-10-CM guideline Section I.C.19.d.

Pabau’s clinical documentation and claims tools support accurate ICD-10-CM coding for burn injury cases.

ICD-10 code T31.74 is a billable ICD-10-CM diagnosis code for burns covering 70-79% of total body surface area (TBSA). Within that, 40-49% of total body surface must be third degree.

Both figures are percentages of the whole body, not proportions of the burned area. That one distinction decides which code in the T31.7 series applies.

This reference covers the code’s hierarchy, the TBSA methods behind it, and the documentation a payer expects. It also covers sequencing against T20-T25 codes and the sibling codes T31.74 is most often confused with.

ICD-10-CM is updated annually by the Centers for Medicare and Medicaid Services (CMS) and the National Center for Health Statistics (NCHS). The FY2026 edition became effective October 1, 2025.

ICD-10 code T31.74: Definition, billable status, and effective date

ICD-10 code T31.74 is a valid, billable ICD-10-CM diagnosis code. It describes burns involving 70-79% of body surface with 40-49% third degree burns, both figures measured against total body surface. The code applies to discharges and encounters from October 1, 2025 onward under the FY2026 edition.

T31.74 in the ICD-10-CM code hierarchy

Knowing where T31.74 sits in the classification tree helps a coder pick the correct code and apply the right sequencing rules. The ancestry chain runs from the broad injury block down to the specific leaf code.

The T31 category classifies burns strictly by extent of body surface involved, not by anatomical site. Site-specific burns are captured separately using T20-T25 codes, which is why sequencing rules matter here.

T31.7X sibling codes: The full 70-79% TBSA series

The fifth character in T31.74 identifies how much of the patient’s total body surface carries third degree, or full-thickness, burns. The fourth character, the 7, fixes total burn coverage at 70-79%. So the fifth character is what separates every code inside the T31.7 subcategory.

Both percentages in the code title measure against total body surface, so no division is required. A patient with 75% TBSA burns and 45% of total body surface in full-thickness injury takes T31.74. If only 35% of total body surface is third degree, the correct code is T31.73. The bands below map each fifth character onto that same scale.

If the documented TBSA falls outside 70-79%, the correct code sits in a different T31 subcategory. The ICD-10-CM diagnostic codes index lists each subcategory and its fifth-character options.

How TBSA is calculated: The Rule of Nines and burn coding

TBSA estimation is a clinical function, not a coder function. The physician documents the calculation and the coder applies the code. Knowing the method helps a coder spot incomplete documentation before the claim goes out.

The Rule of Nines is the standard adult estimation tool. It assigns percentage values to body surface regions as follows:

For pediatric patients, the Rule of Nines produces inaccurate results, because children have proportionally larger heads and smaller lower extremities. The Lund-Browder chart adjusts for age-related surface area variation. It is the preferred method for pediatric burn TBSA estimation, per American Burn Association clinical practice guidelines.

What counts as a third degree burn in ICD-10 coding

Third degree burns are full-thickness injuries that destroy the epidermis and dermis and extend into subcutaneous tissue. The skin cannot regenerate on its own, so grafting is typically required. Burn depth must come from physician documentation, not coder inference, when you assign ICD-10-CM diagnosis codes.

Clinical indicators that physicians document to support a third degree classification include:

• Full-thickness skin destruction confirmed on physical examination
• Insensate wound surface, meaning loss of pain sensation from nerve destruction
• Leathery, waxy, or charred wound appearance
• Absence of blisters, unlike partial-thickness burns
• Requirement for skin grafting or surgical wound closure

Coders cannot independently classify burn depth. If the record does not state “third degree” or “full-thickness” with a documented percentage, query the physician before assigning T31.74.

Documentation requirements for T31.74

Incomplete documentation is the primary cause of T31.74 claim denials. The medical record must contain all of the following before the code can be assigned:

• Total TBSA burned: A numeric percentage confirming total burn coverage between 70% and 79%, supported by a Rule of Nines or Lund-Browder calculation
• Third degree burn percentage: Physician documentation stating that 40-49% of total body surface is full-thickness, not partial-thickness
• Burn depth by body region: Documentation identifying which anatomical areas are third degree and which are second degree
• Clinician attestation: A physician or licensed practitioner must author the burn assessment, not nursing or coding staff
• Date of encounter: Required to confirm the FY2026 edition applies, meaning encounters from October 1, 2025 onward

Practices that submit these claims electronically need the documentation captured in the clinical record before the claim reaches the payer. Practice management software like Pabau sends the encounter to a clearinghouse only once those elements are present. Claims with a missing TBSA calculation get flagged for medical review, which delays payment.

Code sequencing: Using T31.74 alongside T20-T25 burn codes

T31.74 does not stand alone in most burn encounters. The key reference is ICD-10-CM Official Guidelines Section I.C.19.d, which governs the coding of burns and corrosions.

The general principle, consistent with the guidance published through the CDC’s ICD-10-CM coding tool, works like this:

• When the encounter treats the burn injury: Site-specific burn codes (T20-T25) are usually sequenced as principal diagnosis. T31.74 is assigned as an additional code to capture total body surface involvement.
• When burn extent is the overriding clinical focus: T31.74 may be appropriate as principal diagnosis in some inpatient scenarios. That turns on the attending physician’s documentation of the reason for admission.
• Multiple site-specific codes: Each burn location that is clinically significant and independently managed may need its own T20-T25 code. T31.74 then accompanies the full set.

Sequencing can affect DRG assignment and reimbursement directly. Verify the current year’s guidelines against Section I.C.19.d rather than a prior-year interpretation. This matters most when the admission diagnosis and the principal treatment focus differ.

Approximate synonyms and clinical terminology

Several clinical terms map to T31.74. A coder searching an EHR, a physician note, or a discharge summary may meet any of these alternate descriptions:

• Major burn with 70-79% TBSA, 40-49% third degree
• Full-thickness burns over 40-49% of body surface, within 70-79% TBSA
• Third-degree burns involving 40-49% of body surface, with 70-79% TBSA burned
• Burns classified by extent: 70-79% TBSA, 40-49% full thickness
• 70-79 percent body surface area burn with 40-49 percent third degree burns

These approximate synonyms appear in ICD-10-CM reference databases and clinical documentation systems. The code itself does not change with the wording, provided the clinical meaning is equivalent.

Common coding errors to avoid

Most T31.74 errors cluster around two failure modes. One is wrong code selection inside the T31.7 series. The other is documentation that leaves the chosen code undefendable on audit. Both end in appeals, which is why denial management for burn claims begins in the clinical record rather than the billing queue.

• Wrong third degree bracket: Using T31.74 when documentation supports 50-59% third degree involvement, which maps to T31.75. The fifth character must match the documented bracket.
• Treating the fifth character as a ratio: The 40-49% is a share of total body surface, not a share of the burned area. A patient with 72% TBSA burns and 33% of total body surface third degree takes T31.73, not T31.74.
• Using T31.74 as a standalone code: Omitting site-specific T20-T25 codes when individual burn locations are documented and clinically significant.
• No TBSA calculation in the chart: Without a documented method, a payer cannot verify the 70-79% threshold, so the code is unsupported.
• Applying adult TBSA methods to children: Rule of Nines without a Lund-Browder adjustment can shift the case into a different T31 subcategory.

A clean claim for T31.74 needs documentation that closes off each of these error types before it leaves the facility.

Coding for comorbidities: Inhalation injury and burn wound infection

Patients with burns over 70% TBSA frequently present with comorbidities that need their own ICD-10-CM codes. Two of the most common are inhalation injury and secondary wound infection.

Inhalation injury: Smoke inhalation and respiratory burns need separate ICD-10-CM coding beyond T31.74. The right additional code depends on the type of inhalation injury documented. Common options include the T59.X range for toxic effects of other gases, or J68.0 for chemical pneumonitis. Verify the choice against the current CMS tabular list inclusion notes for T31, which name the additional codes that apply.

Burn wound infection: A secondary infection complicating a burn wound needs an additional code identifying the organism, where documented. That code sits alongside T31.74 rather than replacing it. Payers vary on sequencing for complication codes, so check payer-specific guidance before submission.

T31.74 code history and ICD-10-CM effective date

T31.74 has been part of ICD-10-CM since the US transition from ICD-9-CM. CMS and NCHS maintain the US adaptation of the WHO ICD-10 classification for domestic use.

The code description has stayed stable since the transition, with no substantive revisions to its definition. Re-confirm validity each year against the CMS ICD-10-CM update files, because the code set is revised effective every October 1.

How Pabau supports accurate burn injury coding and documentation

Burn cases at this TBSA level generate long documentation requirements and multi-code claims. A loosely structured clinical record is the most common source of T31.74 denials and audit findings.

Pabau’s medical records management lets practitioners build a structured encounter record for a burn admission. One chart holds the TBSA calculation, the burn depth assessment by region, and the comorbidity notes. Its medical claims management then applies built-in ICD-10-CM and CPT catalogues to validate codes before a claim reaches the payer.

For a burn encounter that needs several ICD-10 codes, that structure makes a missing additional code far easier to catch before submission.

Document burn cases once, code them right

Pabau’s structured clinical records capture TBSA calculations, burn depth by region and comorbidity notes in one patient chart. Its claims management validates ICD-10-CM codes before the claim reaches the payer, so T31.74 encounters go out supported.

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Conclusion

T31.74 turns on two numbers that a chart either states or does not. If the physician documents 70-79% TBSA and a third degree share of total body surface between 40% and 49%, the code holds up. If either number has to be inferred, it does not.

The trade-off worth remembering is that querying a physician costs a day, while a denied burn claim costs weeks of appeal. Build the query into the pre-billing step rather than the rework queue.

Book a demo to see how Pabau keeps burn documentation and ICD-10-CM code validation inside the same workflow.

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