Is ICD-10-CM code Z23 billable?

Yes, Z23 (Encounter for immunization) is a billable ICD-10-CM diagnosis code, valid for reimbursement on HIPAA-covered transactions for FY2027.

Is Z23 exempt from POA reporting?

Yes, Z23 is on the CMS list of ICD-10-CM codes exempt from Present On Admission (POA) reporting for FY2027. Inpatient claims do not require a POA indicator for this code.

What chapter does ICD-10-CM code Z23 belong to?

Z23 belongs to Chapter 21 of the ICD-10-CM tabular list: Z00–Z99 (Factors Influencing Health Status and Contact with Health Services).

Z23Billable, valid for claims from October 1, 2026

Encounter for immunization

In Persons with potential health hazards related to communicable diseases (Z20-Z29), chapter 21: Factors Influencing Health Status and Contact with Health Services

Z23 is billable and valid on claims for FY 2027. If the record has more detail, check the other codes under Z20-Z29 below.
As a secondary diagnosis it is not a CC or MCC, so it doesn't raise the MS-DRG payment.
Doesn't count toward a Medicare Advantage risk score (no HCC in V28).
Medicare edits don't accept it as the principal diagnosis. (Unacceptable Principal list)
Exempt from present-on-admission (POA) reporting. (POA Exempt list)

Also indexed as: Admission, prophylactic, vaccination; Immunization, encounter for; Prophylactic, vaccination; Vaccination, encounter for

Instructional notes

Code first: code the underlying condition first, then this code

any routine childhood examination

Code also: add a code for this too, order depends on the encounter

if applicable, encounter for immunization safety counseling (Z71.85)

Official coding guidelines

From the ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027 (CMS and NCHS). Links open the PDF at the right page.

Covers when and how to use Z codes (Z00-Z99) for encounters and supplementary information, including contact, status, history, screening, aftercare, exams, and social determinants of health.

Use of Z Codes in Any Healthcare Setting (page 92)
Z Codes Indicate a Reason for an Encounter or Provide Additional Information about a Patient Encounter (page 93)
Categories of Z Codes (page 93)

Read Section I.C.21 (page 92)

Other codes under Z20-Z29

Persons with potential health hazards related to communicable diseases (Z20-Z29)

Z23 MS-DRGs

As the principal diagnosis, Z23 groups to MS-DRG 795 or 951 (v44.0). Which one applies depends on procedures performed, secondary diagnoses (CC/MCC), and the patient's age and discharge status.

Related conditions

Grouped by AHRQ's Clinical Classifications Software Refined (CCSR), which sorts every diagnosis code into clinically meaningful categories.

Z23 is in Exposure, encounters, screening or contact with infectious disease (FAC016), with 36 codes. Others in it:

G04.02 Postimmunization acute disseminated encephalitis, myelitis and encephalomyelitis
G04.32 Postimmunization acute necrotizing hemorrhagic encephalopathy
Z03.810 Encounter for observation for suspected exposure to anthrax ruled out
Z03.818 Encounter for observation for suspected exposure to other biological agents ruled out
Z05.1 Observation and evaluation of newborn for suspected infectious condition ruled out
Z11.0 Encounter for screening for intestinal infectious diseases
Z11.1 Encounter for screening for respiratory tuberculosis
Z11.2 Encounter for screening for other bacterial diseases

Medicare coverage articles listing Z23

This Medicare billing and coding article lists Z23 as a diagnosis that supports medical necessity for the services they cover. From the CMS Medicare Coverage Database; check your own contractor's article before billing.

Medicare Preventive Coverage for Certain Vaccines

Other codes that refer to Z23

Notes on these codes point to Z23.

Z71.84 Code Also: if applicable, encounter for immunization (Z23)
Z71.85 Code Also: if applicable, encounter for immunization (Z23)

About the condition

Plain-language background from MedlinePlus (National Library of Medicine), not coding guidance.

Vaccines

Vaccines are injections (shots), liquids, pills, or nasal sprays that you take to teach your body's immune system to recognize and defend against harmful germs. For example, there are vaccines to protect against diseases caused by:

Code history

Valid since FY2016, when ICD-10-CM took effect on October 1, 2015.

FY2017: New codes for cases coded here before: Z29.11 (Encounter for prophylactic immunotherapy for respiratory syncytial virus (RSV)), Z29.12 (Encounter for prophylactic antivenin), Z29.13 (Encounter for prophylactic Rho(D) immune globulin), Z29.14 (Encounter for prophylactic rabies immune globulin).

ICD-9-CM equivalent

Legacy crosswalk from the CMS General Equivalence Mappings (last updated 2018).

V05.9 Need for prophylactic vaccination and inoculation against unspecified single disease (approximate)

ICD-9 to ICD-10 converter