2027 ICD-10-CM Diagnosis Code T79.9XXAUnspecified early complication of trauma, initial encounter
T79.9XXA is a billable ICD-10-CM diagnosis code for unspecified early complication of trauma, initial encounter. The 7th character A marks it as an initial encounter code, used while the patient is receiving active treatment. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 922 through 923, 963 through 965. Coders also document this condition as avulsion of maxillary vestibule. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified injury.
T79.9XXA no longer risk-adjusts for Medicare Advantage: it mapped to HCC 173 under the retired CMS-HCC V24 model through payment year 2025 but maps to no category in the live V28 model. It still risk-adjusts in the PACE (CMS-HCC V22) category 173, ESRD (V21) category 173, and ESRD (V24) category 173 for payment year 2027.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
T79.9XXA no longer risk-adjusts for Medicare Advantage: it maps to no payment category in the live CMS-HCC V28 model, although it still risk-adjusts in the other CMS models shown below.
Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Avulsion of maxillary vestibule
- Complex laceration of tongue
- Complication of injury
- Contaminated complex laceration of tongue
- Early complication of trauma
- Laceration of tongue
- Traumatic complication of injury
Coding GuidelinesGuidance
The appropriate 7th character is to be added to each code from block Certain early complications of trauma, not elsewhere classified (T79). Use the following options for the applicable episode of care:
- A - initial encounter
- D - subsequent encounter
- S - sequela
Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027, published by CMS and the National Center for Health Statistics.
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to T79.9XXA: its own notes plus those printed at T79 and Chapter 19. A note printed at a category, block or chapter applies to every code under it.
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
Use Additional Code
Add a second code, after this one, to fully describe the condition.
- code to identify any retained foreign body, if applicable (Z18.-)
Notes
General instructions on how these codes are used.
- Use secondary code(s) from Chapter 20, External causes of morbidity, to indicate cause of injury. Codes within the T section that include the external cause do not require an additional external cause code
- The chapter uses the S-section for coding different types of injuries related to single body regions and the T-section to cover injuries to unspecified body regions as well as poisoning and certain other consequences of external causes.
7th Character
Every code in the category takes a 7th character from the listed values, with the placeholder X filling any empty positions before it.
- The appropriate 7th character is to be added to each code from category T79
- Ainitial encounter this code
- Dsubsequent encounter
- Ssequela
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Convert T79.9XXA to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T79.9XXAOverview
What is the ICD-10 code for unspecified early complication of trauma, initial encounter?
The ICD-10-CM code for unspecified early complication of trauma, initial encounter is T79.9XXA (sometimes written as T799XXA). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is T79.9XXA (Unspecified early complication of trauma) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report unspecified early complication of trauma, initial encounter on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What does the 7th character A in T79.9XXA mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for unspecified early complication of trauma, such as an emergency visit or first evaluation.
What MS-DRG does T79.9XXA group to?
When unspecified early complication of trauma, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 964, 923, 965, 922, 963, with relative weights from 0.9980 to 2.6361 depending on complications. Higher weights mean higher Medicare reimbursement.
What is the ICD-9 equivalent of T79.9XXA?
Under the General Equivalence Mappings, unspecified early complication of trauma, initial encounter converts to ICD-9-CM 958.8 (early complic trauma NEC). The mapping is approximate, so confirm the match fits the documentation.
Does T79.9XXA risk-adjust for Medicare Advantage payment?
Not for Medicare Advantage. T79.9XXA mapped to HCC 173 in the retired CMS-HCC V24 model, which last determined payment in 2025, but it maps to no category in the live V28 model; see all codes that no longer risk-adjust. It still risk-adjusts in the PACE (CMS-HCC V22) category 173 (Traumatic Amputations and Complications), ESRD (V21) category 173 (Traumatic Amputations and Complications), and ESRD (V24) category 173 (Traumatic Amputations and Complications).
