ICD-10 Codes for Traumatic Brain Injury and Head Injury: The Complete 2026 Guide to S06 and S09.90

Head injury coding sends more claims to denial review than almost any other injury category, not because the codes are rare, but because the S00–S09 range is unusually easy to code almost right. A coder picks S06.9X9A instead of a fully specified S06.301A, or reaches for S09.90 when the documentation actually describes a brain injury that belongs under S06, and the claim comes back. This guide covers the full code set for both categories, the rule that trips up more coders than any other in this range, and the documentation that keeps these claims moving.

The S00–S09 Head Injury Range, Briefly

ICD-10-CM groups head trauma under S00–S09, within Chapter 19 (Injury, poisoning, and certain other consequences of external causes). Two categories matter most for TBI and general head trauma billing:

• S06 — Intracranial injury. This is the true traumatic brain injury (TBI) category: concussion, diffuse and focal brain injury, hemorrhage, edema, and brain compression.
• S09.9 — Other and unspecified injuries of head, including S09.90 (unspecified injury of head). This is a catch-all for head trauma that isn't a brain injury, or where documentation doesn't yet establish one.

The distinction between these two categories is where most of the coding confusion in this space actually lives, and it's worth being precise about before touching any subcode. If you need a refresher on how ICD-10 diagnosis codes and CPT procedure codes work together on a claim in the first place, our guide on CPT vs. ICD-10 covers that foundation.

Head trauma also comes up constantly in walk-in settings, if your practice sees these injuries alongside other same-day visits, our urgent care CPT coding guide covers the broader visit and procedure codes that tend to accompany a head injury encounter.

S06: Intracranial Injury — the Core TBI Category

S06 covers "brain injury resulting from an accident, surgery, or other trauma" any bump, blow, jolt, or penetrating injury that damages the brain. It breaks into several subcategories by injury type:

S06.30: Unspecified Focal Traumatic Brain Injury

S06.30 identifies focal TBI where the specific nature of the injury isn't further documented. On its own, S06.30 is not billable, it's a category header, not a complete code. Every claim needs a subcode built around loss-of-consciousness (LOC) duration, plus a 7th character for encounter type.

Every one of these needs a 7th character (A, D, or S, covered below), giving you codes like S06.301A (unspecified focal TBI, LOC 30 minutes or less, initial encounter). Note that 7th characters D and S don't apply to the death-related codes (6th character 7 or 8), for the obvious reason that there's no subsequent or sequela encounter after those outcomes.

The same LOC-duration and 7th-character structure repeats across S06.0 (concussion), S06.2 (diffuse TBI), and S06.9 (unspecified intracranial injury), so once you have the S06.30 pattern down, the rest of the category follows the same logic.

S06.A: Traumatic Brain Compression and Herniation

This subcategory documents brain compression or herniation from trauma, a more severe, specific finding than a general TBI code alone. It's used as an additional code alongside the primary TBI diagnosis when compression or herniation is documented, not as a replacement for it.

S09.90: Unspecified Injury of Head and Why It's Not the Same as S06

This is the distinction that generates real claim denials. S09.90 covers "head injury NOS" head trauma where the documentation doesn't establish a brain injury, and no more specific S00–S08 code applies.

Critically, S09.90 carries an Excludes1 note against:

• Brain injury NOS (S06.9-)
• Head injury NOS with loss of consciousness (S06.9-)
• Intracranial injury NOS (S06.9-)

An Excludes1 note means these conditions cannot be coded together, they're mutually exclusive by definition. If documentation mentions any loss of consciousness, or anything suggesting intracranial involvement, S09.90 is the wrong code; it belongs under S06.9 instead. This exact confusion shows up repeatedly in coder forums: claims get coded as S09.90XA when the clinical picture actually describes a concussion or unspecified intracranial injury, and payers deny the claim as inconsistent with the documented diagnosis.

S09.90 uses a simpler 7th-character structure than S06, since it has no LOC-duration subcodes:

• S09.90XA — Unspecified injury of head, initial encounter
• S09.90XD — Unspecified injury of head, subsequent encounter
• S09.90XS — Unspecified injury of head, sequela

The rule of thumb: if the documentation supports any brain involvement, concussion, LOC, altered mental status, imaging findings, code it under S06, not S09.90. Reserve S09.90 for head trauma (scalp laceration, unspecified face/head contusion, etc.) where no brain injury is documented or suspected.

The 7th Character: Where Most Denials Actually Start

The 7th character (A, D, or S) is required across nearly every code in both S06 and S09.9, and it's the single most common source of denials in this code range, mostly because "initial encounter" is widely misunderstood.

• A — Initial encounter. This does not mean "the patient's first visit ever." It means the patient is receiving active treatment for the injury, ED evaluation, surgery, or any encounter where treatment planning is happening. A patient can have more than one "initial encounter" if they receive active treatment from different providers, and the A character still applies even if the injury happened months earlier, as long as the patient never previously sought treatment for it.
• D — Subsequent encounter. Routine care during the healing or recovery phase: follow-up visits, medication adjustments, or monitoring after active treatment has concluded.
• S — Sequela. A late effect or complication arising from the original injury. Sequela coding always requires two codes: the current condition or symptom first (e.g., R41.844 for frontal lobe/executive function deficit), followed by the injury code with the S character.

Getting the encounter type wrong, most often billing "D" or "S" work as if it were still "A," or vice versa, is one of the fastest ways to trigger a denial or an audit flag in this code range.

Coding TBI Sequela and Related Symptom Codes

Post-TBI symptoms are common, and coding them correctly requires linking the symptom to the original injury:

1. Code the current symptom or condition first, headache, cognitive deficit, insomnia, or a diagnosis like postconcussional syndrome (F07.81).
2. Follow with the TBI code carrying the "S" (sequela) 7th character.

Z87.820 (Personal history of traumatic brain injury) has a narrower role than many coders assume — it applies only when no other code can reflect the previous TBI, and it should not be used alongside a sequela code for the same injury. Z13.850 (encounter for TBI screening) is used regardless of the screening outcome, whether or not a TBI is ultimately found.

Codes Frequently Reported Alongside S06 and S09.9

Head injury claims rarely stand alone. Common accompanying diagnosis codes include:

• S01.- — Open wound of head
• S02.- — Fracture of skull and facial bones
• G93.1 — Anoxic brain damage, not elsewhere classified
• F07.81 — Postconcussional syndrome
• R41.844 — Frontal lobe and executive function deficit

And CPT codes commonly billed for TBI evaluation and management:

• 70450 — CT head/brain without contrast
• 95819 — EEG including recording awake and drowsy
• 96116 — Neurobehavioral status exam
• 97532 — Development of cognitive skills
• 92507 — Speech/language treatment

Many of these pair with standard evaluation and management visits for follow-up care, our breakdown of E/M CPT codes walks through level selection for those visits, and our general CPT codes overview and lookup guide is a useful reference if any of these codes are new to your team. 

Common Coding Errors in This Range

• Billing S06.30 (or any category header) as a standalone code. These are always non-billable without a full subcode and 7th character.
• Coding S09.90 when documentation supports S06.9. The Excludes1 conflict above is the most common version of this error.
• Misapplying "initial encounter." Treating "A" as "first visit" rather than "active treatment," which leads to using D or S prematurely.
• Omitting LOC duration documentation. Without a clearly documented consciousness status and duration, coders default to less-specific, and often non-billable, codes.
• Sequencing sequela codes incorrectly. The symptom code must come first, with the TBI sequela code following, not the reverse.
• Missing combination codes. Comorbid findings like traumatic cerebral edema (S06.1) or anoxic brain damage (G93.1) need their own codes alongside the primary TBI diagnosis, they don't get absorbed into a single code.

Any of these can trigger a denial that then has to be traced, appealed, and resubmitted, the kind of rework our denial management services are built to reduce. 

Documentation Checklist for TBI and Head Injury Claims

To support a fully billable code on the first pass, documentation should establish:

1. Whether loss of consciousness occurred, and its duration if so
2. Whether the injury is diffuse, focal, or another documented type
3. Encounter type, active treatment, recovery-phase care, or treatment of a late effect
4. Any imaging findings supporting the diagnosis (CT, MRI)
5. Associated conditions, skull fracture, open wound, cerebral edema, hemorrhage
6. For sequela claims, the specific symptom or condition being treated

Frequently Asked Questions

What's the difference between S06 and S09.90? 

S06 covers intracranial injury, true traumatic brain injury, including concussion and any injury with documented or suspected brain involvement. S09.90 is for unspecified head injury where no brain injury is documented. They're mutually exclusive under an Excludes1 note; documentation supporting any LOC or intracranial involvement rules out S09.90.

Is S06.30 billable on its own?

No. S06.30 is a category header for unspecified focal TBI. A billable code requires a subcode reflecting LOC status/duration (e.g., S06.301) plus a 7th character for encounter type (e.g., S06.301A).

What does the 7th character "A" actually mean? 

Active treatment for the injury,not simply "the first visit." A patient can have more than one initial encounter across different providers, and the A character still applies even for an old injury if the patient is seeking treatment for it for the first time.

How do you code TBI symptoms that show up after the initial injury has healed? 

Code the current symptom or condition first, then the TBI code with the "S" (sequela) 7th character. Z87.820 is used only when no other code can capture the history, and not alongside a sequela code.

Why do TBI claims get denied so often? 

The most common reasons are billing a non-billable category code (like S06.30 alone), miscoding the 7th character, confusing S09.90 with S06.9, or documentation that doesn't clearly establish LOC duration or encounter type.

Getting These Claims Right the First Time

Head injury coding rewards precision, the difference between a clean claim and a denial is often a single subcode or 7th character. If your practice is seeing repeat denials on S06 or S09.9 claims, or documentation gaps are forcing coders into less-specific codes, RCM Matter's outsourced medical coding services can review your current workflow and help close the gap before claims go out the door.

For more code-specific breakdowns like this one, see our guide to the ICD-10 code for weight loss, part of our ongoing ICD-10 coding series.