Question 1

What is ICD-10 code Y09?

Accepted Answer

Y09 is the ICD-10-CM diagnosis code for assault by unspecified means. An attack or violent act against a person where the specific method or weapon used is not identified or documented. Y09 sits in the ICD-10-CM chapter for external causes of morbidity (v00-y99), within the section covering assault (x92-y09).

Y09 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.

Use only when the assault is confirmed but the means cannot be determined from documentation.

Question 2

Is Y09 an HCC code?

Accepted Answer

No. Y09 is a billable ICD-10-CM code but does not map to any payment HCC category under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can still be reported on Medicare Advantage encounter data submissions, but it does not contribute to the beneficiary's Risk Adjustment Factor (RAF) score and therefore does not affect the risk-adjusted capitation payment to the plan. V28 reached 100% phase-in for payment year 2026.

Question 3

Is Y09 billable?

Accepted Answer

Yes. Y09 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. Y09 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Question 4

What is the V28 vs V24 difference for Y09?

Accepted Answer

Y09 does not map to a payment HCC under either the CMS-HCC V28 risk adjustment model or the older V24 model. V28 reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition. Because neither model rewards Y09 with a risk adjustment factor, it contributes zero to a Medicare Advantage beneficiary's RAF score in either version. Coders should check whether provider documentation supports a more specific child code that does map to a payment HCC.

Question 5

What should coders know when reporting Y09?

Accepted Answer

Use only when the assault is confirmed but the means cannot be determined from documentation Review the record carefully to see if a more specific assault code (Y00-Y08) can be assigned

HCC Buddy Code Card

Y09

Is Y09 an HCC code?

What This Code Means

Coding Tips

Code Hierarchy

Open Y09 in the Interactive Encoder

Y09 ICD-10-CM Code: Assault by unspecified means

HCC Buddy Code Card

Y09

Is Y09 an HCC code?

What This Code Means

Coding Tips

Code Hierarchy

Open Y09 in the Interactive Encoder