A free guide from Cima Consulting
IOP vs. PHP vs. outpatient: an owner's guide to levels of care
Outpatient (OP) is under 9 service hours a week, billed per session. An intensive outpatient program (IOP) is at least 9 hours a week, usually three days of three hours, billed per day with H0015 for substance use or S9480 for mental health. A partial hospitalization program (PHP) is about 20 hours a week, usually five days, billed per day with S0201, with closer medical oversight and closer payer review. Most new programs open IOP and outpatient first and add PHP later. Here's why, level by level, from the team that runs all three in a licensed program.
Updated October 24, 2026. Each payer sets its own hours, codes and criteria in its contract and medical policy; confirm with yours. Not legal or billing advice.
The three levels side by side
| Outpatient (OP) | Intensive outpatient (IOP) | Partial hospitalization (PHP) | |
|---|---|---|---|
| ASAM level (SUD) | Level 1 | Level 2.1 | Level 2.5; "high-intensity outpatient" in the 4th edition |
| Hours a week | Fewer than 9, often 1 to 2 | At least 9 | About 20 |
| Typical schedule | A weekly session or group | 3 days of 3 hours, day or evening | 5 days of 4 to 6 hours |
| Who it fits | Stable, practicing skills, moving toward independent recovery | Needs more than weekly therapy, can keep up with work, school or home | Needs daily treatment and close contact, but is safe at home each night |
| Usually billed | Per session (CPT or H codes) | Per day: H0015 (SUD), S9480 (mental health) | Per day: S0201 |
| Medicare | Paid to eligible clinicians | Since 2024, only via hospital outpatient departments, CMHCs, FQHCs, RHCs and (for OUD) OTPs | Only via hospital outpatient departments and CMHCs |
| Payer review | Light; some plans require authorization | Authorization and concurrent reviews | The closest: short authorizations, frequent reviews |
Every program owner asks the same next question: what does each level take to run? The rest of this page answers it. For the full launch path, see how to start an intensive outpatient program; for PHP specifics, how to start a partial hospitalization program.
ASAM levels and the 4th edition's names
For substance use treatment, most states and many plans use The ASAM Criteria to decide which level a person needs, weighed across six dimensions of need. The level numbers stayed the same in the 4th edition, but some names and the surrounding levels changed:
| Level | 3rd edition name | 4th edition |
|---|---|---|
| 1 | Outpatient services | Outpatient (check the 4th edition for its sub-levels) |
| 2.1 | Intensive outpatient services | Intensive outpatient |
| 2.5 | Partial hospitalization services | High-intensity outpatient (HIOP) |
| 2.7 | Not a level (ambulatory withdrawal management was 2-WM) | Medically managed intensive outpatient |
California's Medi-Cal behavioral health program describes Level 2.5 as renamed high-intensity outpatient treatment services, while payers still use both names: one Blue plan's medical policy covers partial hospitalization for substance use disorders, which it also calls high-intensity outpatient. The treatment industry's own training on the change is a good overview (NAATP, ASAM 4th edition workshop). The 4th edition also reorganizes the dimensions themselves.
What to do about it: write your admission, continued-stay and discharge criteria in the edition your state and each payer require, and keep a line in the policy that maps the old name to the new one, so "PHP" in a contract and "Level 2.5" in a chart are clearly the same service. For mental health programs ASAM doesn't apply; payers use their own medical-necessity guidelines (many use MCG, InterQual or their own; some use LOCUS).
Weekly hours payers expect
Most payers expect at least 9 hours a week for adult IOP and about 20 for PHP. Medicare writes these into the certification: a physician certifies at least 9 hours a week for IOP, and at least 20 hours plus the need for inpatient care otherwise for PHP (Medicare Benefit Policy Manual, chapter 6). Commercial plans set their own minimums in each contract and medical policy, and many count only time in services given by qualified staff: not lunch, breaks or check-in.
Worked example: the schedule template from our program kit
| Time | Service | Who attends |
|---|---|---|
| 9:00–10:30 | Process group with check-in and a safety screen | PHP Mon–Fri; day IOP Mon, Wed, Thu |
| 10:30–10:40 | Break (not counted) | Everyone |
| 10:40–12:10 | Skills group on the curriculum topic of the day | PHP Mon–Fri; day IOP Mon, Wed, Thu |
| 12:10–12:50 | Lunch (not counted) | PHP |
| 12:50–2:20 | Specialty group: family, trauma-informed care, wellness or relapse prevention | PHP |
| 2:20–3:00 | Individual sessions, case management, psychiatric visits | PHP; IOP by appointment |
- Day IOP: two 90-minute groups, three days a week, is exactly 9 hours. Miss one day and the client is at 6 for that week, so the weekly individual session and a make-up policy matter.
- PHP: three 90-minute groups a day is 4.5 hours, or 22.5 a week, before individual and psychiatric time. Lunch and breaks aren't counted.
- Evening IOP: 6:00–7:30 and 7:40–9:10, three evenings a week, is also 9 hours.
Attendance has to prove these hours. An EHR that records minutes per service and totals them by week, like Cima EHR's Program plan, catches a short week before the authorization review does.
Typical billing codes
Programs commonly bill a daily rate. Each plan decides which code and claim form it accepts, so confirm in every contract:
| Level | Common HCPCS or CPT (CMS-1500) | Common revenue codes (UB-04) |
|---|---|---|
| PHP | S0201 per diem; some plans want H0035 or H2012 | 0912, 0913 |
| SUD IOP | H0015 per diem | 0906 |
| Mental health IOP | S9480 per diem | 0905 |
| Outpatient | Per session: 90791 (assessment), 90832, 90834, 90837 (individual), 90853 (group); some SUD plans use H0001 (assessment) and H0004 (counseling) | Varies by plan |
- Medicare marks partial hospitalization claims with condition code 41 and intensive outpatient claims with condition code 92 (CMS MLN MM13222).
- A plan that has paid your PHP days under one code may deny them under another. Track which code each plan has actually paid, not just what the contract says, and bill that way.
- Cima EHR bills per diem on the code you set for each level and plan; see Cima for IOP and PHP programs. Before admission, verify benefits with the VOB checklist and get the prior authorization.
Staffing by level
The staff a program needs grows with the hours each client spends there. Credential rules come from your state (in Texas, counseling in an SUD program is by or under qualified credentialed counselors; see the Texas IOP and PHP guide), so check yours.
- Outpatient: licensed clinicians on a schedule, with supervision for associates and interns.
- IOP: counselors who lead groups and carry caseloads, a clinical director who supervises, a medical director under contract, and someone who owns intake and utilization review.
- PHP: everything in IOP, plus more clinical hours per client every day, daily access to a prescriber, and often nursing.
For scale, the example our financial projection starts from, a 24-client program split 40% PHP and 60% IOP, staffs a program and clinical director, three counselors, an intake and UR coordinator, a behavioral health tech and a contract medical director at a fifth of full time: about $34,300 a month with payroll taxes. That's an assumption to start the conversation, not a staffing rule; see the full example budget. The staffing plan, job descriptions and credential files are part of the program launch package, built for the levels you choose.
Which to open first, and why
Most new programs should open IOP with outpatient step-down first, then add PHP:
- Less to staff and build. Three days of three hours needs fewer clinical hours per client, less space and no lunch area. An evening track serves people who work.
- Lighter review while you learn. Your utilization review habits get built on the level payers watch less closely.
- PHP needs somewhere to step down to. Every PHP client's plan names the next level. Without your own IOP, you hand clients to someone else at the moment they're ready to step down.
- Outpatient keeps people connected after IOP, and is often the level self-pay clients can afford.
Open PHP from day one only if your referral base clearly needs it (hospitals or residential programs in your area with nowhere to send people who still need a full treatment day), you can staff the medical side, and your target plans contract for it. The pull is real: in our example, a PHP client five days a week at $400 a day brings in about $2,000 a week against about $675 for an IOP client three days at $225. But those dollars come with the closest review any outpatient level gets. Adding PHP later is covered in adding PHP to an IOP.
Whatever you open, the license, the policy manual, the criteria and the payer contracts should name every level you might add, so adding PHP later is a staffing change, not a new application. That's how we write them in the IOP / PHP Program Launch.
Questions
What is the difference between IOP and PHP?
Hours and intensity. IOP is at least 9 hours a week, usually three days, for people who can keep up with daily life; PHP is about 20 hours a week, usually five days, for people who need daily treatment and close monitoring but can go home at night.
Is PHP the same as inpatient?
No. PHP clients go home every night. It's the most intensive outpatient level, often used to step down from a hospital or residential stay or to avoid one.
What's the difference between IOP and outpatient?
IOP is a structured program of at least 9 hours a week, mostly groups, usually billed per day. Outpatient is fewer than 9 hours, often one session a week, billed per session.
How long does a client stay in IOP or PHP?
As long as they meet the criteria for that level. It isn't a fixed number of weeks: the payer reviews progress at each authorization, and the treatment plan names the signs that the client is ready to step down.
What does ASAM Level 2.5 mean now?
It's the level traditionally called partial hospitalization. The 4th edition of The ASAM Criteria calls it high-intensity outpatient, and many payers use both names.
Does insurance cover IOP and PHP?
Most commercial plans and many Medicaid programs do, with authorization and medical-necessity review. Medicare covers them only from certain provider types, which leaves out most freestanding programs.
Deciding which levels to open?
The IOP / PHP Program Launch designs your levels, schedule and ASAM-based criteria, writes the license application and policies, and contracts with eight plans, for $24,500 flat.
Or book a free 30-minute call and talk it through with people who run all three levels.
Sources
- California DHCS, BH-CONNECT and CalAIM workgroup slides: ASAM 4th edition level names.
- Excellus BlueCross BlueShield, medical policy: partial hospitalization for substance use disorders.
- NAATP, ASAM 4th edition workshop slides.
- CMS, CY 2024 outpatient (OPPS) final rule fact sheet: Medicare IOP benefit.
- CMS, Medicare Benefit Policy Manual, chapter 6: PHP and IOP certification.
- CMS, MLN MM13222: condition codes for PHP and IOP claims.
- Schedule, codes, staffing and example rates: Cima Consulting's program kit and financial projection (2026).