ICD code T31.33 – Third-degree burns covering 30-39% of the body

Key takeaways

T31.33 covers burns involving 30-39% of body surface, with 30-39% of the body burned to third degree.

The fifth character tracks the third-degree share of the whole body: T31.30 is 0-9% or unspecified, T31.31 is 10-19%, and T31.32 is 20-29%.

T31.33 is the primary code only when the burn site is unspecified. Otherwise it follows the T20-T25 site codes as a supplementary code.

T31.33 takes no seventh character, so the encounter type (A, D or S) rides on the T20-T25 site codes.

External cause codes come from X00-X19 for fire and hot substances, or W85-W87 for electrical burns.

ICD-10 code T31.33 means a third of the body is burned to full thickness

ICD-10 code T31.33 is the billable ICD-10-CM code for burns involving 30-39% of body surface with 30-39% third degree burns. Both numbers sit in the same band, so nearly the whole burned area is full thickness. It belongs to category T31, which sorts burns by extent rather than by body site.

In practice, you’ll see it on major burn admissions, usually beside site codes from T20-T25. The table holds the reference data, and you can browse neighboring codes in the ICD-10-CM code library.

The fifth character tracks the third-degree share, not the total burn

In T31.3x, the fourth character fixes the total burn at 30-39% of body surface. The fifth character records how much of the whole body is burned to third degree: 0-9, 10-19, 20-29 or 30-39%. Both figures are measured against total body surface, never against the burned area alone.

The chart below shows the same ladder at a glance. Only the third-degree band moves, while the total burn stays put.

Depth has to come from the provider’s documentation. Coders shouldn’t infer it from nursing notes or wound care orders alone. If the record is unclear, query the provider.

A note stating 25% third degree belongs on T31.32, not T31.33. With no third-degree figure at all, T31.30 is the default.

The rule of nines sets the two percentages T31.33 depends on

The rule of nines is the standard way to estimate TBSA for burn coding. The percentages in the provider’s note decide which T31 code applies, as the CMS ICD-10 resources and official guidelines set out.

Here’s a worked example. A patient has burns to both arms (18%) and the front of the trunk (18%), so the total is 36%. The surgeon documents full thickness on both arms and half the anterior trunk.

That makes 18% plus 9%, or 27% third degree. The correct code is T31.32, not T31.33. T31.33 applies only once the third-degree share reaches 30% of the body.

For children, the Lund-Browder chart adjusts for a larger head. The official guidelines also let providers adjust the percentages for infants, children, and patients with large buttocks, thighs, or abdomen. Either way, the provider should name the method used in the note.

The T31 note: T31.33 goes first only when the burn site is unspecified

Category T31 carries one instructional note, and it settles sequencing. In the Tabular List, it reads:

“This category is to be used as the primary code only when the site of the burn is unspecified. It should be used as a supplementary code with categories T20-T25 when the site is specified.”

So a patient with documented third-degree burns of the trunk and arms gets the site codes first. Sequence the code for the highest-degree burn first, then add T31.33 for the overall extent. T31.33 adds data to the site codes, and it never replaces them.

T31.33 takes no seventh character, but its partner codes do

Does T31.33 need a seventh character? No. This trips up coders who work across burn categories, because T20-T25 site codes always take one. A marks the initial encounter, D a subsequent one, and S a sequela.

Encounter type for a T31.33 claim lives on those companion site codes. Getting that split right is part of sound medical billing workflows for burn cases.

Codes that usually travel with T31.33 on the same claim

T31.33 rarely appears alone. A burn this size brings extra diagnoses and procedures, and each needs its own code.

When the record documents inhalation injury, code it separately, whatever the principal diagnosis. Grafts need the same care. A split-thickness autograft on the trunk, arms, or legs is reported with CPT code 15100 for the first 100 sq cm.

How a T31.33 claim moves from admission to payment

A major burn claim passes through several hands. Here’s the usual path, step by step.

1. Admission note: The provider records total TBSA, the third-degree share, the method used, and how the burn happened.
2. Coding: The coder assigns the T20-T25 site codes with seventh character A, highest degree first. T31.33 and the external cause codes follow.
3. Authorization: The billing team checks the plan’s inpatient rules and sends the TBSA documentation with any request.
4. Procedures: Each graft or debridement code points to the site diagnosis it treats.
5. Submission and follow-up: The claim is checked, sent, and tracked until the remittance posts. Denials get corrected and resubmitted.

Documentation that holds T31.33 up under review

Five elements carry a T31.33 claim through review. Without them, nobody can defend the third-degree share, and the claim may stall or move to a lower T31.3x code. clean claim submission depends on the record capturing them before billing starts.

• TBSA percentage with calculation method: The provider documents the total (30-39%) and names the rule of nines or Lund-Browder chart.
• Third-degree share: A stated percentage of body surface burned to full thickness (30-39%), attested by the provider rather than inferred from nursing notes.
• Cause of burn: Fire, hot liquid or object, electricity, or another source. It drives the external cause code, X00-X19 for fire and hot substances or W85-W87 for electricity.
• Encounter type: Initial, subsequent, or sequela, carried by the seventh character on the T20-T25 site codes.
• Complications: Inhalation injury, infection, sepsis, and grafting should be documented and coded when present.

Before you submit: A quick T31.33 claim checklist

Run through this list before the claim leaves the building. Each line maps to a common reason burn claims come back.

• Both percentages are in the provider note: total burn and third-degree share, each 30-39%.
• The calculation method is named.
• T20-T25 site codes are present, each with its seventh character, highest degree first.
• T31.33 sits after the site codes, unless the site is unspecified.
• An external cause code is attached (X00-X19, or W85-W87 for electrical burns).
• Inhalation injury, infection, or sepsis is coded where documented.
• Every graft or debridement code links to the matching site diagnosis.
• Any required authorization number is on the claim.

Payer rules vary, so check authorization before you bill

Burns of this size and depth almost always mean an inpatient stay. Authorization rules differ by plan and change often, so confirm them early.

• Medicare and Medicare Advantage: Rules differ between traditional Medicare and individual Advantage plans, so check the specific plan.
• Medicaid: State programs vary. Transfers to a burn center often need their own authorization.
• Commercial payers: Requirements vary by payer. Verify inpatient and procedure authorization rules with each plan.
• Burn center transfers: Requests move faster when the note already states TBSA, depth, and the reason for transfer.

Common mistakes that get T31.33 claims denied

Most denials on extent-based burn claims trace back to documentation or sequencing. These are the slips worth catching first, and solid denial management strategies help with the rest.

• Missing TBSA percentage: The note gives no figure, so T31.33 can’t be defended over a lower T31.3x code.
• Depth not provider-attested: Depth appears only in nursing notes or wound flowsheets, which payers may treat as insufficient.
• Wrong fifth character: T31.33 is reported when under 30% of the body is third degree. Or T31.30 is used when the record supports a higher share.
• T31.33 sequenced first: The extent code leads even though the burn sites are documented.
• Missing external cause code: No X00-X19 or W85-W87 code explains how the burn happened.
• Diagnosis and procedure mismatch: A graft code points to a diagnosis that doesn’t support its medical necessity.
• Wrong sequela coding: A healed burn is coded as active instead of with the sequela structure.

Follow-up and sequela visits change the code set

Once the burn has healed, the coding structure changes. A sequela visit for scarring, contracture, or rehab leads with the residual condition. The T20-T25 site code follows with seventh character S.

The guidelines describe T31 for acute burns, so T31.33 usually drops off once the burn has healed. While a burn is still healing, it’s coded as acute.

• Initial treatment: T20-T25 site codes with A, then T31.33 for extent.
• Ongoing care while the burn heals: Site codes with D, with T31.33 still available for extent data.
• Sequela (scar, contracture, rehabilitation): The residual condition first, such as L90.5 for a scar, then the site code with S.
• Grafts during healing: The graft CPT code, linked to the site diagnosis it treats.

How Pabau keeps complex burn claims moving

A T31.33 admission can carry a long list of diagnosis codes, several graft procedures, and an authorization. Many teams still build that claim by hand and track it in a spreadsheet. A missing field then shows up weeks later as a rejection.

Pabau is the practice management platform we build, and its claims software for practices pre-fills each claim from the patient record. Coders search ICD-10-CM and CPT codes from built-in lookup libraries. Required fields are checked before the claim can be sent.

In the US, claims go out through Claim.MD, with real-time eligibility checks and ERA remittance posting. Your team spends less time re-keying codes and more time on the claims that need a person.

Streamline complex burn claim submissions

Pabau pre-fills claims from the patient record, checks required fields before sending, and tracks each claim to payment through Claim.MD.

Book a demo

Conclusion

T31.33 rests on two numbers in the provider’s note: the total burn and the third-degree share. When both sit in the 30-39% band, the code follows. When either is missing, query the provider before billing.

A one-line addendum costs far less than an appeal on an inpatient burn stay. Building the site, extent, and cause codes at admission feels slow on a busy unit. It’s still faster than reworking a denial weeks later.

Book a demo to see how Pabau pre-fills burn claims from the record and tracks each one to payment.

Continue your research

Managing claim denials on complex diagnosis codes? Denial management in healthcare covers the strategies high-complexity practices use to prevent and resolve denials before they age.

Need to understand the clearinghouse submission process? Claim.MD clearinghouse guide explains how Pabau’s clearinghouse integration routes 837P claims and returns ERA remittances.

Looking for clean claim best practices? Clean claim submission guidance outlines the data completeness checks that prevent front-end rejections.

Coding a smaller third-degree share? ICD-10 code T31.31 covers 30-39% burns where 10-19% of the body is third degree.

Working a larger burn? ICD-10 code T31.44 covers burns of 40-49% of body surface with 40-49% third degree.

Frequently asked questions