PHP and IOP Billing for Substance Use Treatment Facilities: What Makes It Different

Billing for a PHP or an IOP is nothing like billing for office visits. There isn't one session and one claim. You have programs that run for hours a day, several days a week, paid by the day, sitting behind authorizations that have to be renewed on a schedule, with payers that each want their own codes. Small differences in how a day is documented can decide whether the whole day gets paid.

This is a plain look at how that billing works for substance use treatment programs, where the denials tend to come from, and why Medicare is mostly not part of the picture.

PHP and IOP in plain terms

Both are structured outpatient programs. Patients go home at night, but they spend a big part of the week in treatment. The difference is how big.

An intensive outpatient program (IOP) usually means at least 9 hours of treatment a week, over at least three days. A partial hospitalization program (PHP) is more intense: usually 20 or more hours a week, often five days. In the ASAM criteria, which most payers use to decide what level of care a patient needs, these are Level 2.1 and Level 2.5. The fourth edition of the criteria came out in late 2023 and payers have been adopting it on their own schedules, so ask each payer which edition and which hour thresholds it applies.

How these programs get billed

Most payers pay these programs per day rather than per session. The codes you will see most often are H0015 for substance use IOP, S9480 for psychiatric IOP, and S0201 or H0035 for PHP, depending on the payer. Some payers use H2036, another per day alcohol and drug treatment code, instead. On the facility claim, IOP is often reported with revenue code 0905 for psychiatric care or 0906 for substance use.

Which code a payer wants is a contract question more than a coding question. Two payers can pay the same program under different codes, and the right service billed under the wrong code will deny. Get the code, the revenue code, what counts as a unit and the daily rate in writing when you contract, and check them again whenever the payer sends a policy update.

Authorization decides a lot

One industry review of the criteria says virtually all major commercial payers require prior authorization for IOP before the program starts. For PHP, payers want documentation that the patient would otherwise need hospital-level care. After that comes concurrent review, typically every 5 to 10 sessions for IOP and every 5 to 7 days for PHP. Every review is a chance to lose days.

The clinical record also has to support the level of care you billed. If the notes don't, claims can be denied, or paid and then taken back later. That means the billing side and the clinical side need to talk every week about who is due for review and what the payer needs to see.

Where the denials come from

One billing guide for IOP programs lists the usual causes. A missing or expired authorization. Billing two units on the same day, for example a mental health day and a substance use day for the same patient, which payers can treat as duplication. Days beyond what was approved. And thin documentation, or days shorter than the code expects. Some payers look for at least three hours for an IOP day.

The fix is not clever, it's just consistent. Check benefits for the specific level of care before the first day. Keep a tracker with authorization dates and approved days. Make sure the notes support the hours before the claim goes out. And work denials by reason, so you can see which cause is costing you the most. Our guide on reading a claim denial is a good starting point for that.

Why Medicare is mostly not part of the picture

People often say Medicare won't let these programs be "in network." The reality is a little different, and it matters for billing. Original Medicare doesn't use networks at all. What it has instead is enrollment: a provider is either a type of organization that Medicare pays for a service, or it isn't. For PHP and IOP, the benefit is tied to where the program operates.

Medicare Part B covers partial hospitalization when it is delivered by a hospital outpatient department or a community mental health center. It is described as an alternative to inpatient psychiatric care, and a provider has to certify that the patient would otherwise need inpatient treatment. Medicare added coverage for intensive outpatient programs on January 1, 2024. The settings that can furnish and bill it are hospital outpatient departments, Medicare-certified community mental health centers, federally qualified health centers, rural health clinics and, for opioid use disorder, opioid treatment programs. According to a summary from the Center for Health Care Strategies, other community-based substance use treatment facilities are not authorized to bill Medicare for IOP. Check current CMS guidance on telehealth before assuming virtual sessions are covered.

So a standalone treatment center licensed by the state as a substance use facility generally falls outside the benefit. To bill Medicare it would need to operate as one of the covered types, which usually means a different structure with its own certification and requirements, not just extra paperwork.

In practice, a patient with Original Medicare who walks into a standalone program often can't have that program billed to Medicare. Find that out at verification, before day one, not after the first claim. Medicare Advantage is different, because those plans run their own networks and each plan decides which programs it contracts with. Call the plan and ask directly whether it will authorize and pay for PHP or IOP at your facility, and under which codes. For most programs like these, commercial insurance and Medicaid will do most of the paying, so that is where the contracts and state rules matter.

Questions to ask before you take on a payer

Which level-of-care criteria and which edition do they use? Which codes and revenue codes do they want, and what is a unit? Is prior authorization required, and how many days are approved at a time? How often is review? What is the daily rate? And what does the claim need to show to be paid? If you can get those answers in writing, most of the surprises go away.

This kind of billing rewards careful tracking more than anything else, and it's the work we do with substance use and behavioral health programs. If you want to see what that looks like for yours, read about our behavioral health billing, our questions to ask before outsourcing billing, or just talk to us.

This article is general information, not legal or financial advice. Medicare rules, payer policies and state requirements change and vary, so confirm current details with each payer and with CMS. Sources: Medicare.gov, Partial hospitalization; CMS, CY 2024 OPPS final rule fact sheet; Center for Health Care Strategies, New changes to intensive outpatient program coverage; Ensora Health, IOP billing codes; Bluebrix, ASAM criteria and levels of care.

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