Partial Hospitalization (PHP) and Intensive Outpatient (IOP) are structured programs, not just a series of appointments. Payers (especially Medicare) have strict rules. The biggest question you must answer is: are you billing per-diem or fee-for-service?

Per-Diem (Medicare Standard)

This is the most common model for facility billing. You are paid one flat rate for all services provided on a given day.

PHP (Partial Hospitalization):

• Requires 20+ hours per week.
• Billed on a UB-04 form with Bill Type 013x and Revenue Code 0912.

IOP (Intensive Outpatient):

• Requires 9-19 hours per week.
• Billed on a UB-04 form with Bill Type 013x and Revenue Code 0913.

Key Billing Rules

• No Unbundling: Under per-diem, you cannot bill individual psychotherapy codes (90834), group codes (90853), or prescriber visits (9921x) on the same day. It is all included in the per-diem rate.
• Minimum Hours: The patient must meet the minimum hours for the program. If a PHP patient only attends 15 hours one week, you must bill that week as IOP.
• Commercial Payers: This is the trap. Many commercial payers do not use per-diem and require you to bill fee-for-service (i.e., bill 90834, 90853, 99213 all on the same claim).

The Payer Policy Trap