Z23 — Encounter for immunization
Is Z23 billable?
Yes — Z23 is billable for FY2027. Z23 is a valid, billable ICD-10-CM code at the highest level of specificity in its branch. Z23 may be submitted for encounters from October 1, 2026 through September 30, 2027.
Z23 at a glance
| Code | Z23 |
|---|---|
| Description | Encounter for immunization |
| Billable | Yes |
| Code set | ICD-10-CM FY2027 |
| Valid for encounters | October 1, 2026 – September 30, 2027 |
What Medicare edits apply to Z23?
The Medicare Code Editor screens inpatient claims before they are grouped. These edits name Z23 directly.
CMS will reject this code as the principal diagnosis on an inpatient claim. It describes something other than the condition chiefly responsible for the admission.
Which MS-DRGs does Z23 group to?
Z23 sits in MDC 15 and helps define the logic of 1 MS-DRG (version 44, FY2027). Which one a stay actually groups to also depends on procedures and secondary diagnoses.
- 795Normal Newbornmedical
How is Z23 listed in the Alphabetic Index?
These are the routes through the Alphabetic Index that lead to Z23. They show the wording a clinician may have documented, which often differs from the Tabular description.
- Immunization › encounter for
- Prophylactic › vaccination
- Vaccination › encounter for (prophylactic)
- Admission › prophylactic › vaccination (for)
Code first
The underlying condition below must be sequenced before Z23. Z23 describes a manifestation and cannot be the principal or first-listed diagnosis.
- any routine childhood examination
Code also
Two codes may be needed to describe the condition fully. Whether Z23 is sequenced first depends on the reason for the encounter.
- , if applicable, encounter for immunization safety counseling (Z71.85)
Note
- procedure codes are required to identify the types of immunizations given
How long has Z23 existed?
Z23 has been in ICD-10-CM since at least FY2016, the earliest fiscal year on record here.
Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.