In ABA therapy billing, one billing unit represents 15 minutes of service.

Standard Category I CPT codes, such as 97153 (direct therapy), 97155 (protocol modification), and 97156 (family guidance), are all billed in these 15-minute increments. The total number of units reported on an insurance claim reflects the exact duration of care provided during a session.

To ensure accurate billing, providers often follow the 8-minute rule (or mid-session rule) to determine how to round units:

• At least 8 minutes of a 15-minute block must be completed to count as one unit.
• For example, a session lasting 23 minutes would be billed as 1 unit, whereas a session lasting 24 minutes would be billed as 2 units.
• A 53-minute session would be billed as 3 units.

It is important to calculate units separately for each specific CPT code used, as minutes from different codes cannot be combined.

• ABA Therapy CPT Codes: Complete Guide for Providers