IOP & PHP Billing Services

Intensive outpatient (IOP) and partial hospitalization (PHP) programs bill a bundle of therapy services on a schedule, often by the day. Payers care about program hours, medical necessity, and a plan of care that is reviewed on time. A claim can fail if the level of care, the codes, or the paperwork do not line up.

IOP and PHP billing also splits by payer. Medicare, Medicaid, and commercial plans each use different rules for facility claims, per diem rates, and authorizations. Westmont Revenue Partners connects behavioral health programs with vetted billing experts who understand these differences and can support the full revenue cycle.

Who this is for

• Hospital-based and freestanding IOP and PHP programs
• Community mental health centers running day programs
• Mental health and dual-diagnosis treatment centers
• Programs serving adults, teens, or both
• Operators adding a step-down level of care after residential or inpatient treatment

What gets billed

• Group psychotherapy sessions
• Individual psychotherapy sessions
• Family psychotherapy with or without the patient
• Psychiatric evaluations and medication management
• Psychological testing when ordered
• Activity therapy and skills groups
• Patient education and training services
• Per diem program days for commercial and Medicaid plans
• Intake assessments and treatment plan reviews
• Physician certification and recertification of the plan of care

Commonly billed codes

Code	Type	What it covers
G0410	HCPCS	Group psychotherapy for partial hospitalization or IOP
G0411	HCPCS	Interactive group psychotherapy for partial hospitalization or IOP
90853	CPT	Group psychotherapy
90837	CPT	Individual psychotherapy, about 60 minutes
90834	CPT	Individual psychotherapy, about 45 minutes
90846	CPT	Family therapy without the patient present
90847	CPT	Family therapy with the patient present
S9480	HCPCS	Per diem for intensive outpatient psychiatric services, used by some commercial and Medicaid payers
0905	Revenue code	Intensive outpatient services, psychiatric, on facility claims
0906	Revenue code	Intensive outpatient services, chemical dependency

Note

Codes are examples for orientation, not a complete list, and do not guarantee coverage or payment. Always check current code sets and payer policy.

Billing challenges in IOP and PHP

• Medicare versus commercial billing. Medicare IOP began in 2024 for certain settings and uses facility claims with specific revenue and condition codes. Commercial plans may want per diem codes instead. Billers set up each payer's format separately.
• Plan of care and certification. Medicare requires a physician certification and regular plan reviews. Missing or late signatures can put payment at risk. Billers track due dates and flag gaps before claims go out.
• Level of care authorization. Payers authorize days or hours and review them often. Billers submit clinical updates on schedule and record the authorization number on each claim.
• Bundled services. Some payers pay one daily rate and bundle other services into it. Billers learn which codes are packaged so they do not bill items that will be denied.
• Who can bill. Not every site can bill Medicare IOP. Eligible settings include hospital outpatient departments, community mental health centers, rural health clinics, and federally qualified health centers. Billers confirm your enrollment first.
• Hours and attendance documentation. Payers expect proof of program hours. Billers compare attendance logs to billed days to catch gaps.
• Revenue code mapping. Facility claims need the right revenue code paired with the right procedure code. Billers use a crosswalk and review it each year.

How Westmont can help

• Matching you with vetted billing experts experienced in IOP and PHP programs
• End-to-end revenue cycle support, from verification to payment posting
• Denial management for authorization and level-of-care issues
• Help with payer enrollment and credentialing for programs and clinicians
• Reporting that shows claims by payer and level of care

Frequently asked questions

What is the difference between IOP and PHP billing?

PHP is a higher level of care with more hours per week than IOP. Payers set separate rules, rates, and authorization steps for each. Medicare also has distinct requirements for each program. Always confirm the level of care a plan has approved before you bill.

Does Medicare cover IOP?

Medicare began covering intensive outpatient services in 2024 for hospital outpatient departments, community mental health centers, rural health clinics, federally qualified health centers, and opioid treatment programs. Details and rates change each year, so check current CMS and MAC guidance before you bill.

Which revenue code do we use for IOP?

Revenue code 0905 is generally used for psychiatric IOP services on Medicare facility claims. Some payers want different codes. Check the payer manual. A biller should confirm the code and procedure pairing before the first claim, since errors can delay every claim after.

Can we bill per diem or by service?

It depends on the payer contract. Medicare uses a single daily payment for IOP, while many commercial and Medicaid plans use per diem codes such as S9480 or bill each service. Review each contract and set up your system to follow it.

Why are our IOP claims denied for medical necessity?

Common causes are missing treatment plans, weak progress notes, or hours that do not meet the plan's criteria. A biller can review denial patterns, work with your clinical team on documentation, and appeal where records support the level of care.

Related billing services

• Psychiatry Billing
• Addiction Medicine Billing
• Community Mental Health Center Billing
• Counseling & Therapy Billing
• Hospital Billing