ICD code T31.83 – Burns across 80-89% of the body, 30-39% third degree

Key takeaways

T31.83 covers burns across 80-89% of total body surface with 30-39% full-thickness, and it records extent only, never site.

T31.83 is usually an additional code rather than the principal diagnosis, because a documented T20-T25 site code outranks it.

A missing third-degree percentage drops the claim to T31.80, and a missing total TBSA removes T31 from the claim.

External cause codes are not federally mandated, so check your state and payer rules before treating them as required.

Pabau’s claims management software files T31.83 claims electronically through a clearinghouse, then tracks eligibility, claim status and remittances.

ICD-10 code T31.83 classifies burn extent, not burn site

ICD-10 code T31.83 is the billable diagnosis code for burns covering 80 to 89 percent of the body. Of that burned area, 30 to 39 percent has to be documented as third degree, meaning full-thickness.

The code belongs to category T31, which groups burns by how much of the body is involved rather than which part. It is valid and billable for fiscal years 2025 and 2026, confirmed by the CDC/NCHS ICD-10-CM code tool.

Two axes define the code. The first is total burn extent, at 80-89% TBSA. The second is the depth qualifier, at 30-39% third degree. Both have to come from the treating physician before the code holds up on a claim.

T31.83 at a glance

Where T31.83 sits in the ICD-10-CM tabular list

T31.83 is the last link in a five-level chain inside the ICD-10-CM classification. Knowing where it sits makes the sequencing rules easier to apply, and it catches crosswalk errors before a payer does.

• Chapter 19: Injury, poisoning, and certain other consequences of external causes (S00-T88)
• Block T30-T32: Burns and corrosions of multiple and unspecified body regions
• Category T31: Burns classified according to extent of body surface involved
• Subcategory T31.8: Burns involving 80-89% of body surface
• Code T31.83: Burns involving 80-89% TBSA with 30-39% third degree

Only the final digit moves. It carries the third-degree proportion. T31.80 means no third-degree burns were documented, and T31.83 means 30 to 39 percent of the burned area is full-thickness. That digit changes the DRG weight the grouper lands on, which makes it a reimbursement decision as much as a coding one.

Thermal burns are in, corrosions and sunburn are out

T31.83 is an extent-only code. It tells a payer how much of the body burned and how deep the worst of it goes, but it never says where.

Burn versus corrosion is a frequent audit flag. Payers return claims where T31.83 was used for a chemical injury that belonged in T32.83. The mechanism the physician wrote down is what decides which category applies.

One digit separates this code from its neighbors

Every code in the T31.8x subcategory shares the same 80-89% extent. Only the final digit changes, and each value stands for a different clinical picture and a different DRG weight. Picking the wrong one is the most common coding error in this subcategory.

T31.83 counts the burn, T20-T25 name the body part

T20-T25 codes say where the burn is, on the face, the hand, the trunk or a lower limb. T31.83 says how much of the body it covers. Section I.C.19.d of the ICD-10-CM Official Guidelines expects both sets on the same claim, and AHA Coding Clinic guidance says the same.

Take a patient admitted after a house fire with burns to the chest wall, the right shoulder and both legs. The physician records 84% TBSA with 35% full-thickness. The coder assigns a T20-T25 code for each burned site, then adds T31.83 for the total extent. Neither set stands in for the other.

• Use T20-T25 codes to: name the anatomical burn locations, support site-specific procedures such as hand grafts, and meet medical record specificity standards
• Use T31.83 to: capture total burn extent, support burn center admission criteria, and drive the DRG grouper into MDC 22
• Use both together whenever the sites are documented and the total comes to 80-89% TBSA with 30-39% third degree

Two percentages decide whether the chart supports T31.83

The record has to carry both numbers in the physician’s own words. Missing the third-degree percentage is not the same failure as missing the total, and the two lead somewhere different.

Two validated tools support the estimate itself. The Rule of Nines splits the adult body into regions of roughly 9% each. The Lund-Browder chart adjusts those proportions for age. That makes it the correct tool for children, where the adult rule reads high and becomes a compliance risk.

Four elements belong in the record before a T31.83 claim goes out. The physician, not the coder, has to state each one.

1. Total TBSA burned – a specific percentage such as “82% TBSA”, not a range and not an estimate without a number
2. Third-degree percentage – the share of the total burn that is full-thickness, such as “35% third degree”
3. Burn depth assessment – confirmation of full-thickness depth for the areas counted as third degree
4. Mechanism of injury – flame, scald, chemical, electrical or radiation, which also drives the external cause code

Each of those fails differently, and this is where coders most often go wrong. Without a stated total TBSA, no code in the T31.8x range applies at all, and the claim carries only the site codes.

Leave out the third-degree percentage and the supportable code drops to T31.80. Depth and mechanism notes feed other parts of the code set, so their absence weakens the record without changing that default.

The chart below walks the same three checks in the order a coder meets them.

Which codes travel with T31.83 on the claim

T31.83 rarely goes out alone. External cause codes are the companions coders ask about most, and the rule is narrower than it looks. Section I.C.20 of the ICD-10-CM Official Guidelines sets no national requirement to report them.

Reporting becomes mandatory only where a state, a payer contract or a specific program says so, and it stays voluntary everywhere else.

That makes the external cause code a local question rather than a federal one. Check your own payer mix first, because a burn center billing three states can easily be under three different rules.

A compliant code set for that house-fire admission runs in this order.

1. T22.351A – burn of third degree of the right shoulder, initial encounter
2. T21.31XA – burn of third degree of the chest wall, initial encounter
3. T31.83 – the total extent, reported as an additional code
4. X00.0XXA – exposure to flames in an uncontrolled building fire
5. Y92.009 – unspecified place in an unspecified private residence

The site code for the highest-degree burn leads the claim. T31.83 follows it, because the burned sites are documented and the extent code is supplementary here. Watch the shoulder code in particular: T22.311 is the right forearm, and the right shoulder is T22.351.

T31.83 is rarely the principal diagnosis

Is T31.83 ever the principal diagnosis? Yes, but in one situation only. Section I.C.19.d of the ICD-10-CM Official Guidelines assigns T31 codes as additional codes for extent. They lead the claim only when the burn site is not specified.

So on a chart that names the burned sites, the highest-degree T20-T25 code is principal and T31.83 is supplementary. A coder who puts the extent code first has inverted the set, which is worth checking on any burn claim you inherit.

Two other situations are worth knowing. Outpatient coding follows the reason-for-the-visit rule rather than the most-severe-burn rule, so confirm the encounter type before you sequence.

Where one site drives its own surgery, such as a circumferential hand burn needing emergent escharotomy, that site code may lead for that encounter. The AAPC ICD-10-CM code lookup carries sequencing notes for each code.

CPT codes that show up alongside T31.83

Burns at this extent need staged procedures across a long inpatient stay, so the CPT side of a T31.83 claim is rarely short. The codes below are the ones burn centers bill most often against this diagnosis.

Sequencing on the procedure side matters less than on the diagnosis side, but the volume does not help anyone. A single admission can generate dozens of lines across several weeks, so the billing team needs a clear view of what has already gone out.

Why T31.83 claims get denied, and what stops it

T31.83 denies more often than most diagnosis codes, because every element of the two-axis descriptor has to be traceable in the chart.

The patterns below are specific to burn coding, and a coder who knows them can clear most of the risk before submission.

• No TBSA percentage in the physician notes: the most common denial. Nursing estimates do not substitute for physician documentation, so request an addendum before the claim goes out.
• No third-degree percentage: the supportable code is then T31.80, not T31.83. A one-digit upcoding error draws fraud-and-abuse attention during an audit.
• Missing external cause code: some payers and state programs require one, while national guidelines do not. Check the rule that governs your claim rather than assuming either way.
• Burn coded as a corrosion: chemical injuries need T32.83. Using T31.83 for one fails the payer edits that cross-check mechanism against code selection.
• TBSA inconsistency between providers: nursing notes at 85% against a physician at 78% is a conflict, and auditors read it as unsupported specificity.
• Stale code validity: confirm T31.83 is valid for the date of service. ICD-10-CM updates take effect every October 1.

On the remittance side, a handful of CARC values come back again and again. CARC 16 means the claim lacks information. CARC 50 says the service was not judged medically necessary. CARC 4 flags an inconsistent modifier. The denial codes reference maps each one back to the documentation a payer is asking for.

Preventing all of that is mostly a documentation exercise rather than a billing one. If you want the wider version of this workflow, the clean claim guide covers the same pre-submission review across other high-acuity encounters.

What Medicare pays: MDC 22 and DRGs 928 and 929

Under Medicare, a T31.83 admission groups to MDC 22, the burns category, and usually lands in DRG 928 or DRG 929. Both of those cover full-thickness burns with a skin graft or an inhalation injury. What separates them is a complication or comorbidity, so DRG 928 applies with a CC or MCC and DRG 929 without one.

DRG weights change every fiscal year, so check the current CMS IPPS tables before quoting a figure to anyone. Medicaid prior authorization for burn center admission varies by state and contract year, which makes it a conversation with the payer rather than an assumption.

Most commercial payers use American Burn Association referral criteria to authorize the admission. Burns at 80-89% TBSA clear those thresholds comfortably, but the criteria still have to reach the payer with the authorization request. Treat this as general practice and verify it with each payer, since none of it is a policy statement.

How Pabau moves a T31.83 claim out the door

A burn center admission produces a long claim with many moving parts. Most billing teams assemble it in the chart, rekey it into a payer portal, then wait for a remittance to tell them what went wrong.

Practice management software like Pabau closes that loop. Pabau’s claims management software files the claim electronically through a clearinghouse and runs eligibility checks before the encounter. Remittance advice then posts back against the claim it belongs to, so the billing team can see status without logging into a portal.

The coding judgment stays with your team. Pabau handles the mechanical work of submission, claim status and reconciliation. A coder then spends more time on the chart and less of it chasing a payer.

Send burn claims out electronically with Pabau

Pabau files claims through your clearinghouse, runs eligibility checks before the encounter, and posts remittance advice back against the claim it belongs to.

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Conclusion

T31.83 rewards a coder who reads the chart twice. The code itself is straightforward, and the two percentages behind it are the whole argument you are putting to a payer.

If you take one habit away from this page, make it the sequencing check. A burn chart that names its sites puts a T20-T25 code first, with T31.83 behind it. Get that order wrong and the grouper lands on a different DRG, quietly, with no warning on the remittance.

What follows is process, and process is where software earns its place. Book a demo to see how Pabau files a burn admission electronically and posts the remittance back against it.

Continue your research

Want to decode the denial that came back? Denial codes in medical billing maps each CARC and RARC code to the documentation a payer is asking for.

Want to build a clean claim workflow for complex diagnoses? Claim.MD clearinghouse guide explains how electronic claims validation catches errors before they reach the payer.

Looking to understand revenue cycle management for high-acuity encounters? What is revenue cycle management covers the end-to-end process from coding to payment posting.

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