ICD-10 code T31.44: Burns involving 40-49% TBSA with 40-49% third degree

ICD-10 code T31.44 is the billable ICD-10-CM diagnosis code for burns involving 40-49% of total body surface area (TBSA) where 40-49% of that burned surface consists of third-degree (full-thickness) injuries. Burn units see this code applied when TBSA assessment confirms extensive damage spanning nearly half the body, with a substantial proportion reaching the deepest wound classification.

Accurate code selection between T31.40 and T31.44 determines MS-DRG assignment, reimbursement weight, and audit risk. This reference covers code structure, TBSA methodology, the T31.4x subcode decision matrix, documentation requirements, and the T31 versus T32 distinction.

Burn coding carries higher audit exposure than most diagnosis categories. Claims for major burns like T31.44 are scrutinised by Medicare, commercial payers, and Recovery Audit Contractors because the reimbursement weight is substantial and documentation errors are common. Getting the fourth digit wrong by one notch (e.g., using T31.43 when 40% of the TBSA is third-degree) can trigger a denial or overpayment flag.

Found our content helpful?

Key Takeaways

T31.44 is a billable ICD-10-CM code covering 40-49% TBSA burns where 40-49% of that area is third-degree (full-thickness) injury, valid for FY2026 encounters from October 1, 2025.

The fourth digit in the T31.4x series reflects what proportion of the total burned surface is third-degree: T31.40 = none, T31.41 = under 10%, up to T31.44 = 40-49%.

TBSA is typically calculated using the Rule of Nines for adults; the Lund-Browder chart is preferred for pediatric patients due to age-related body proportion differences.

T31 codes cover thermal burns classified by extent; T32 codes cover corrosions. The burn mechanism, not depth alone, determines which category applies.

ICD-10 code T31.44: quick reference at a glance

The table below covers the core reference data coders and clinicians need before billing or documenting a T31.44 encounter. All details reflect the FY2026 ICD-10-CM edition.

What does ICD-10 code T31.44 mean clinically?

ICD-10 code T31.44 means the patient has sustained thermal burns covering 40-49% of their total body surface area, with 40-49% of that burned area classified as third-degree (full-thickness) injury. Third-degree burns destroy the epidermis, dermis, and underlying subcutaneous tissue; they present as dry, leathery, or waxy wounds that are insensate at the burn site because the sensory nerve endings are destroyed.

The clinical picture at T31.44 is a major burn injury requiring intensive care. Patients typically need fluid resuscitation calculated from the Parkland formula, surgical debridement, and skin grafting over large surface areas. The plastic surgery EMR workflows that support these cases must capture wound-depth mapping at each surgical encounter, because coding at discharge can differ from the admission code if depth assessments are refined during treatment.

Two clinical distinctions matter for coding accuracy. First, third-degree burns are distinct from deep partial-thickness (deep second-degree) burns. Deep partial-thickness burns spare some dermal appendages and may be moist with reduced sensation; third-degree burns have none. Conflating the two changes the fourth digit. Second, the 40-49% TBSA range means both the total burn extent and the third-degree subset must independently fall in that band for T31.44 to apply.

T31 burn coding TBSA: How the category structure works

The T31 category organises burn diagnoses by the percentage of body surface area involved rather than by anatomical location. This is the key distinction between T31 and the anatomically specific burn codes (T20-T25). When a burn spans multiple body regions, T31 provides a single code that reflects overall injury severity based on extent.

The first digit after the decimal sets the TBSA range. T31.0 = less than 10% TBSA; T31.1 = 10-19%; T31.2 = 20-29%; T31.3 = 30-39%; T31.4 = 40-49%; T31.5 = 50-59%; continuing in 10% increments through T31.9 (90% or more). The hemorrhagic diagnosis coding system uses a parallel structure, showing how ICD-10-CM frequently encodes severity through digit position rather than separate code categories.

How the Rule of Nines determines your TBSA percentage

The Rule of Nines assigns a fixed percentage of body surface area to each anatomical region for adult patients. Clinicians sum the involved regions to obtain TBSA. The standard adult assignments are:

• Head and neck: 9%
• Each upper extremity: 9% (18% total)
• Anterior trunk: 18%
• Posterior trunk: 18%
• Each lower extremity: 18% (36% total)
• Perineum / genitalia: 1%

To reach 40-49% TBSA, a clinical scenario might include the full posterior trunk (18%), both upper extremities (18%), and partial involvement of one lower extremity (9% reaching 45% total). The Lund-Browder chart is preferred for patients under 15 because head-to-leg proportions shift significantly during development; the Rule of Nines overestimates head involvement and underestimates leg involvement in young children. Any TBSA documentation citing these figures should specify the assessment tool used, per CMS ICD-10-CM coding guidelines.

Understanding the fourth digit: Third-degree burn percentage in T31.4x

The fourth digit in the T31.4x subcategory specifies what proportion of the established TBSA burn consists of third-degree injury. This is a nested percentage: it applies to the burned area only, not to the patient’s total body surface.

In practical terms, if a patient has a 45% TBSA burn and 20 of those 45 percentage points are third-degree (roughly 44% of the burned area), T31.44 applies because the third-degree proportion falls in the 40-49% range. If only 10 of the 45 TBSA points are third-degree (22% of the burned area), T31.42 applies instead.

Note that the T31.4x series does not include a code for 30-39% third-degree within the 40-49% TBSA range. T31.43 covers 20-29%, and T31.44 jumps to 40-49%. There is no T31.43.5. Coders who calculate 30-35% third-degree proportion apply T31.43 (the closest lower bound), which underscores why precise wound-depth mapping documentation is critical. Reviewing ICD-10-CM diagnosis coding patterns across clinical conditions illustrates how digit precision throughout the code set drives reimbursement accuracy.

T31 vs T32: Burns versus corrosions

T31 and T32 are parallel code categories: T31 covers thermal burns classified by extent; T32 covers corrosions (chemical burns) classified by extent. The mechanism of injury, not the wound depth or TBSA, determines which category applies.

A common coding error is applying T31.44 to a chemical plant injury where a corrosive agent caused the wound. The clinical appearance can be identical to a flame burn, but the ICD-10-CM Official Guidelines require the mechanism to drive category selection. Good practice is checking the emergency department note or incident report for language like “acid exposure,” “alkali splash,” or “chemical burn,” which should route the claim to T32.44 rather than T31.44.

Burn coding documentation requirements for T31.44

Supporting T31.44 through a claim requires specific documentation elements that go beyond the code description itself. Most burn coding denials stem from missing TBSA measurement detail or inadequate burn-depth characterisation, not from the wrong code selection. Solid medical billing compliance practice means the clinical record must answer four questions before the claim leaves the facility.

• Total TBSA percentage: The physician or advanced practice provider must document the total burned surface area as a percentage, specify the assessment tool used (Rule of Nines for adults, Lund-Browder for pediatric patients), and confirm the figure falls in the 40-49% range.
• Third-degree burn percentage: The depth-specific breakdown must be documented separately from total TBSA. A note stating “45% TBSA burn” does not support T31.44 without a corresponding statement like “of which approximately 42% is third-degree (full-thickness) injury.”
• Wound mapping or body surface diagram: Many burn centres complete a front-and-back body diagram at admission and update it at each surgical encounter. This diagram provides the audit trail connecting the percentage figures to specific anatomical locations.
• Burn depth characterisation: The clinical note must distinguish third-degree from deep partial-thickness using accepted terminology. “Full-thickness,” “insensate,” “dry/leathery wound,” and “eschar formation” are all defensible clinical descriptors. “Severe burn” or “deep burn” alone is not sufficient.
• Mechanism of injury: Thermal cause (flame, scald, contact, radiation, electrical) must be documented to support T31 over T32.

When the burn team revises depth estimates between admission and discharge (which is clinically normal as oedema resolves and wound demarcation becomes clearer), the discharge summary should explain any change from the admission code. Pabau’s claims management software allows billing teams to flag encounters where diagnosis codes were updated mid-stay, reducing the risk that an outdated admission code is submitted at discharge. Ensuring a clean claim submission means the final code aligns with the discharge summary, not the ED triage note.

MS-DRG and reimbursement implications of T31.44

T31.44 maps to MS-DRG groups within the burn injury family under Medicare’s Inpatient Prospective Payment System (IPPS). Burns are one of the highest-complexity and highest-cost DRG categories because of the ICU stays, multiple surgical procedures, and extended rehabilitation they typically require. The specific MS-DRG assigned to a T31.44 encounter depends on procedure codes billed alongside the diagnosis, discharge disposition, and whether the case qualifies as a Major Complication or Comorbidity (MCC).

Under the IPPS grouping logic, extensive burns with significant third-degree involvement (T31.44 included) commonly fall within MS-DRG 927 (Extensive Burns or Full Thickness Burns with MV 96+ Hours with Skin Graft) or related burn DRG pairs, depending on ventilator hours and skin grafting procedures performed. MS-DRG weights and payment amounts are updated annually in the CMS IPPS Final Rule; coders should verify current-year weights against CMS ICD-10-CM and IPPS documentation before relying on any published figure.

Effective revenue cycle management for burn cases means the billing team should expect payer requests for clinical records, particularly when the MS-DRG weight is high. Pre-submission checklist: confirm TBSA documentation supports the T31.44 level, confirm procedure codes for grafting match operative reports, and check whether secondary diagnoses (sepsis, inhalation injury, fluid overload) are coded and sequenced correctly, since they influence DRG assignment and may qualify as MCCs. Effective medical billing workflows for high-complexity burn encounters build in a clinical documentation improvement (CDI) touchpoint before claim submission.

Submitting T31.44 claims through Claim.MD clearinghouse integration enables real-time eligibility verification before admission and electronic remittance advice (ERA) on adjudication, so billing teams can identify and work denials on burn claims without manual payer portal logins. Denial management in healthcare for major burn cases often centres on TBSA documentation gaps rather than code-level errors, making the CDI-to-billing handoff the highest-leverage intervention point.

ICD-10-CM 2026 update: Is T31.44 still valid?

T31.44 is a valid, active ICD-10-CM code for FY2026. The code became effective October 1, 2025, under the annual ICD-10-CM update cycle maintained by CMS and the National Center for Health Statistics (NCHS). No revisions to the T31.44 descriptor or its position in the T31 hierarchy were made in the FY2026 update.

The ICD-10-CM code set is updated every October 1. For any code, verifying the current edition against the CDC/NCHS ICD-10-CM web tool before billing is the most reliable way to confirm billable status and check for new inclusion or exclusion notes. T31.44 has maintained the same description across recent FY editions, but downstream coding guidelines, payer policies, and MS-DRG assignments can change even when the code itself does not.

ICD-10-CM codes are also published alongside official ICD-10 diagnostic code references for other categories, which can help coders understand coding conventions that apply system-wide, such as the use of seventh-character extensions for injury sequencing. T31.44 does not require a seventh character, but related site-specific burn codes (T20-T25) do use the seventh character to indicate initial encounter (A), subsequent encounter (D), or sequela (S).

Approximate synonyms and clinical terminology for T31.44

Several clinical and administrative terms map to T31.44. Coders may encounter these in physician notes, operative reports, or trauma documentation and should recognise them as equivalent expressions of the same diagnosis.

• Burns involving 40-49% body surface area with 40-49% full-thickness burns
• Major burn with 40-49% TBSA and 40-49% third-degree injury
• Extensive thermal burn, 40-49% total body surface area, 40-49% third-degree
• 40 to 49 percent total body surface area burn with 40 to 49 percent full-thickness involvement
• Burn classified by extent – 40-49% TBSA, 40-49% third degree
• ICD-10-CM T31.44 (abbreviated form used in burn registries and trauma databases)

When the clinical record uses “full-thickness” rather than “third-degree,” the terms are clinically interchangeable for coding purposes. ICD-10-CM burn coding accepts both. “Deep partial-thickness” and “deep second-degree” are not synonyms for third-degree and should not be coded as T31.44 unless a physician explicitly re-characterises the wound as full-thickness on a later assessment. Reviewing the superbill documentation practices used in burn units can clarify how these terms flow from clinical assessment into the billing record.

Manage burn unit billing without the documentation gaps

Pabau’s claims management tools help burn care teams track diagnosis codes from admission through discharge, flag mid-stay code changes, and submit clean claims. See how it works for high-complexity inpatient coding.

Book a demo

Conclusion

The central challenge with ICD-10 code T31.44 is documentation specificity. The code is valid and billable for FY2026, but claims fail when TBSA figures and third-degree percentages are recorded as combined totals rather than as separate, clearly documented measurements.

Pabau’s claims management software supports burn billing teams by linking diagnosis code assignments to the clinical encounter record, making it straightforward to reconcile the admission code against the discharge summary before submission.

For burn units managing high-complexity inpatient claims, getting T31.44 right from documentation to DRG assignment reduces denial exposure and supports accurate reimbursement. To see how Pabau handles complex inpatient billing workflows, review how electronic remittance advice works within the Claim.MD integration.

Continue your research

Need to understand how burn claims move through the clearinghouse? Claim.MD clearinghouse overview explains how electronic claims submission works for complex inpatient diagnoses.

Want to reduce burn coding denials before they happen? Denial codes in medical billing covers the most common CARC denial reasons and how to address them at the documentation stage.

Looking for a reference on the 837 claim format used for inpatient billing? 837 file guide walks through the electronic claim format that carries T31.44 and other inpatient diagnoses to payers.

Frequently Asked Questions