Summary & Overview
HCPCS S9475: Ambulatory Substance Abuse Treatment or Detoxification, Per Diem
HCPCS Level II code S9475 denotes per diem substance abuse treatment or detoxification services provided in an ambulatory (outpatient) setting. This code is used to bill daily program-based care for patients receiving medically supervised detox or structured substance use disorder treatment without inpatient admission. Nationally, such services are a critical component of addiction care delivery and are increasingly relevant amid ongoing efforts to expand access to outpatient treatment pathways and reduce reliance on inpatient detox.
Key payers in typical analyses include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of what S9475 represents, how it maps to ambulatory detox and substance abuse program billing, and which major payers commonly cover these services. The publication also outlines benchmarking context, common billing practices, and policy considerations that affect coverage and payment for per diem outpatient substance abuse services.
This summary is intended for clinicians, billing professionals, and policy analysts seeking a national-level reference on S9475, including coding intent, sites of service, and the types of information to consult when evaluating reimbursement or coverage policies.
Billing Code Overview
HCPCS Level II code S9475 represents ambulatory setting substance abuse treatment or detoxification services, billed per diem. The service type is substance abuse treatment / detoxification, delivered in an ambulatory outpatient setting where patients receive one-day or daily program services without inpatient admission.
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Clinical & Coding Specifications
Clinical Context
A 34-year-old patient with severe opioid use disorder presents for entry into an ambulatory detoxification and substance abuse treatment program billed under S9475 (ambulatory setting substance abuse treatment or detoxification services, per diem). The patient arrives for intake, receives a comprehensive assessment by a licensed behavioral health clinician, medication-assisted treatment initiation (if indicated), daily counseling, nursing observation for withdrawal symptoms, and care coordination with community resources. Typical workflow: registration and insurance verification; initial medical and psychiatric evaluation; urine drug screen and vital sign monitoring; medication dosing (e.g., buprenorphine) and observation; individual or group counseling sessions; case management for housing and social services; discharge planning with follow-up appointments and referral to higher level of care if needed. Services are billed per diem for each day of ambulatory detoxification or structured substance abuse treatment provided in an outpatient clinic, community program, or ambulatory treatment center.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
00 | Default – no modifier | Use when no special reporting modifier applies to the per diem service |
22 | Increased procedural services | Use if the daily service required substantially greater intensity or time than usual for S9475 |
23 | Unusual anesthesia | Rarely used for ambulatory detox; use if unexpected anesthesia was required during the day |
29 | Professional component | Use if billing only the professional component of a split per diem service when applicable |
52 | Reduced services | Use when the per diem program was partially furnished or services were less than usual for the day |
53 | Discontinued procedure | Use if the day’s treatment was started but discontinued due to patient condition or transfer |
55 | Postoperative management only | Use when only follow-up or monitoring was provided without active detox interventions |
62 | Two surgeons | Use if care during the day involved two collaborating physicians sharing responsibility |
QX | Ordering/servicing provider with private compliance (modifier for lab) | Use when applicable laboratory services associated with the per diem are billed with modifier linkage to an authorized provider arrangement |
QY | Laboratory test performed for a provider-performed microscopy | Use when associated point-of-care testing is performed by a qualified lab performing provider on-site |
AS | Physician assistant, nurse practitioner, or clinical nurse specialist services for Medicare beneficiaries | Use when the per diem services are furnished by a PA, NP, or CNS and billing rules require this modifier |
CO | Multiple payors; payment contingency | Use when coordination of benefits or payer-specific billing requires indicating other primary payors (commercial coordination) |
CQ | Delivery of service furnished under a grant | Use when the ambulatory treatment per diem is furnished under a federally funded grant program requiring tracking |
SH | Speech-language pathology services | Use only if speech therapy is delivered as part of co-occurring treatment on the same day |
| Taxonomy Code | Specialty | Notes |
|---|---|---|
2084P0800X | Addiction Medicine | Medical management of detoxification and medication-assisted treatment |
208D00000X | Psychiatry & Neurology | Psychiatric evaluation, medication management, comorbid mental health care |
171M00000X | Substance Use Disorder Counseling | Behavioral counseling, group and individual therapy services |
363L00000X | Clinical Social Work | Case management, discharge planning, community resource linkage |
368N00000X | Nurse Practitioner | Day-to-day medical monitoring, medication initiation, and nursing oversight |
Related Diagnoses
| ICD-10 Code | Description | Clinical Relevance |
|---|---|---|
F11.20 | Opioid dependence, uncomplicated | Common primary diagnosis for ambulatory detoxification and medication-assisted treatment billed under S9475 |
F10.20 | Alcohol dependence, uncomplicated | Frequent diagnosis for patients receiving ambulatory alcohol detox and structured treatment per diem |
F12.20 | Cannabis dependence, uncomplicated | Used when patients receive ambulatory treatment and withdrawal monitoring for cannabis use disorder |
F13.20 | Sedative, hypnotic or anxiolytic dependence, uncomplicated | Relevant for ambulatory detoxification from benzodiazepines or similar agents |
F19.20 | Other psychoactive substance dependence, uncomplicated | Covers detox and treatment for stimulants or polysubstance dependence in an ambulatory setting |
Related CPT Codes
| CPT Code | Description | Relationship to This Procedure |
|---|---|---|
99205 | Office or other outpatient new patient visit, typically 60–74 minutes | Used for the comprehensive initial medical evaluation on day of admission to the ambulatory detox per diem when a new patient requires in-depth assessment |
99214 | Office or other outpatient established patient visit, typically 40–54 minutes | Used for follow-up medical management visits during the course of ambulatory detoxification |
96127 | Brief emotional/behavioral assessment (e.g., standardized screening) | Used for routine brief screenings for depression, anxiety, or substance use severity during the per diem encounter |
80305 | Drug screen, presumptive, multiple drug classes | Used for urine or point-of-care drug screening performed as part of intake or monitoring during the ambulatory detox per diem |
99406 | Smoking and tobacco use cessation counseling, intermediate, greater than 3 minutes up to 10 minutes | Used when brief counseling for tobacco use is provided as part of the comprehensive substance use treatment per diem |
90853 | Group psychotherapy (other than of a multiple-family group) | Used for group counseling sessions delivered during the ambulatory substance abuse treatment per diem |