The Eight ABA CPT Codes

The AMA introduced the current ABA CPT code set (97151–97158) in 2019, replacing the older H-code billing structure. Understanding what each code covers, who can bill it, and how to apply modifiers correctly is fundamental to ABA billing.

97151 — Behavior Identification Assessment

What it covers: The functional behavior assessment (FBA) or behavior identification assessment conducted by a BCBA or BCaBA under BCBA supervision. Includes record review, caregiver interview, direct observation, and report writing.

Who can bill it: BCBA (no modifier) or BCaBA under BCBA supervision (modifier HO or HN depending on payor).

Unit structure: 15-minute units. Most payors authorize 8–16 units (2–4 hours) for an initial assessment.

Key billing rules:

  • Cannot be billed on the same day as 97152 by the same provider
  • The assessment must result in a written report
  • Re-evaluations are billed under 97151 with modifier 52 for some payors

    • 97152 — Behavior Identification Supporting Assessment

    What it covers: Observation and data collection conducted by a technician (RBT or BT) as part of the behavior identification assessment. The technician is collecting data under the direction of the BCBA conducting the 97151.

    Who can bill it: RBT or BT under BCBA supervision (modifier HM or HN depending on payor).

    Key billing rules:

  • Must be billed in conjunction with 97151 on the same date of service
  • The supervising BCBA must be physically present or immediately available
  • Some payors (notably Medicaid programs) do not cover 97152 separately

    • 97153 — Adaptive Behavior Treatment by Protocol

    What it covers: Direct ABA therapy delivered by a technician (RBT or BT) implementing a treatment protocol developed by the supervising BCBA. This is the most commonly billed ABA code.

    Who can bill it: RBT or BT under BCBA supervision (modifier HM).

    Unit structure: 15-minute units. Authorizations typically specify weekly hours.

    Key billing rules:

  • The supervising BCBA must review session notes and provide supervision at the required ratio
  • Telehealth billing is permitted by most payors with modifier 95 or GT
  • Place of service codes: 02 (telehealth), 11 (office), 12 (home), 99 (other)

    • 97154 — Group Adaptive Behavior Treatment by Protocol

    What it covers: ABA therapy delivered to 2 or more clients simultaneously by a technician implementing a treatment protocol.

    Who can bill it: RBT or BT under BCBA supervision.

    Key billing rules:

  • Bill once per client per session (not once per group)
  • Group size limits vary by payor (typically 2–4 clients per technician)
  • Some payors require prior authorization specifically for group services

    • 97155 — Adaptive Behavior Treatment with Protocol Modification

    What it covers: Direct therapy delivered by a BCBA that includes modifying the treatment protocol based on data analysis. This is the BCBA-delivered direct therapy code.

    Who can bill it: BCBA (no modifier) or BCaBA under BCBA supervision (modifier HO).

    Key billing rules:

  • Cannot be billed simultaneously with 97153 for the same client by the same provider
  • The BCBA must be directly providing therapy, not supervising a technician
  • Some payors limit the number of 97155 units relative to 97153 units

    • 97156 — Family Adaptive Behavior Treatment Guidance

    What it covers: Parent/caregiver training conducted by a BCBA or BCaBA. Includes training caregivers to implement behavior intervention strategies.

    Who can bill it: BCBA (no modifier) or BCaBA under BCBA supervision (modifier HO).

    Key billing rules:

  • The client does not need to be present for 97156 to be billed
  • Most payors authorize a limited number of 97156 units per authorization period
  • Documentation must reflect specific skills taught to the caregiver

    • 97157 — Multiple-Family Group Adaptive Behavior Treatment Guidance

    What it covers: Parent/caregiver training delivered to multiple families simultaneously.

    Who can bill it: BCBA or BCaBA under BCBA supervision.

    Key billing rules:

  • Bill once per family per session
  • Rarely authorized separately — most payors include it under the general 97156 authorization

    • 97158 — Group Adaptive Behavior Treatment with Protocol Modification

    What it covers: Group ABA therapy delivered directly by a BCBA with protocol modification.

    Who can bill it: BCBA or BCaBA under BCBA supervision.

    Key billing rules:

  • Bill once per client per session
  • Requires prior authorization from most payors

    • Modifier Quick Reference

    ModifierMeaningWhen to Use
    HMLess than master's degreeRBT/BT delivering 97152, 97153, 97154
    HNBachelor's degreeBCaBA delivering 97151, 97155, 97156
    HOMaster's degreeBCBA delivering 97151, 97155, 97156
    95Synchronous telemedicineTelehealth sessions (most payors)
    GTInteractive audio/videoTelehealth sessions (some Medicaid programs)
    U1–U9State-specificRequired by some Medicaid programs

    The Five Most Common ABA Billing Errors

    1. Wrong modifier for provider type. Using HO (master's degree) for an RBT delivering 97153. The correct modifier for RBT-delivered services is HM.

    2. Billing 97153 and 97155 simultaneously. A BCBA cannot bill 97155 (BCBA direct therapy) and 97153 (technician therapy) for the same client at the same time. These codes are mutually exclusive during the same time period.

    3. Missing place of service code. Telehealth sessions require POS 02 (or 10 for patient's home telehealth). Using POS 11 (office) for a telehealth session will result in a denial.

    4. Exceeding authorized units. Billing more units than authorized, particularly for Anthem (weekly limit) and other payors with strict unit caps.

    5. Incorrect diagnosis code. ABA services must be billed with an ASD diagnosis code (F84.0 for Level 1, F84.1 for Autistic Disorder, etc.). Using a related but non-ASD diagnosis code (e.g., F80.9 for speech delay) will result in a denial.