Question 1

What is ICD-10 code Z66?

Accepted Answer

Z66 is the ICD-10-CM diagnosis code for Do not resuscitate. A patient has a documented order indicating they do not wish to be resuscitated in the event of cardiac or respiratory failure. Z66 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. Z66 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Question 2

Is Z66 an HCC code?

Accepted Answer

No. Z66 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 Z66 billable?

Accepted Answer

Yes. Z66 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. Z66 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 Z66?

Accepted Answer

Z66 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 Z66 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 Z66?

Accepted Answer

This code documents the presence of a DNR order; ensure it's clearly documented in the medical record and communicated to all care team members Use this code to flag the patient's wishes for end-of-life care planning and to ensure appropriate care decisions

HCC Buddy Code Card

Z66

Is Z66 an HCC code?

What This Code Means

Coding Tips

Code Hierarchy

Open Z66 in the Interactive Encoder

Z66 ICD-10-CM Code: Do not resuscitate

HCC Buddy Code Card

Z66

Is Z66 an HCC code?

What This Code Means

Coding Tips

Code Hierarchy

Open Z66 in the Interactive Encoder