Why Modifiers Matter in ABA Billing

Modifiers are two-character codes appended to CPT codes that provide additional information about the service rendered. In ABA billing, modifiers primarily communicate the credential level of the provider delivering the service. Getting modifiers wrong is one of the leading causes of ABA claim denials.

The Credential-Level Modifiers

The three credential-level modifiers used in ABA billing correspond to the provider's highest degree:

HM — Less Than Master's Degree

Used for Registered Behavior Technicians (RBTs) and Behavior Technicians (BTs) delivering direct therapy.

Use with: 97152, 97153, 97154, 97158

Example: An RBT delivering 4 hours of direct ABA therapy bills: 97153 HM × 16 units

HN — Bachelor's Degree

Used for BCaBAs (Board Certified Assistant Behavior Analysts) and other providers with bachelor's-level credentials.

Use with: 97151, 97155, 97156, 97157 (when delivered by BCaBA)

Note: Some payors use HN for BCaBAs and HO for BCBAs. Others use HO for all BCBA-level providers regardless of whether they hold a master's or doctoral degree. Always verify with the specific payor.

HO — Master's Degree

Used for BCBAs delivering assessment, direct therapy, or parent training.

Use with: 97151, 97155, 97156, 97157 (when delivered by BCBA)

Note: BCBAs with doctoral degrees (BCBA-D) typically still bill with HO unless the payor specifically recognizes a doctoral-level modifier.

Telehealth Modifiers

95 — Synchronous Telemedicine Service

The standard telehealth modifier accepted by most commercial payors and an increasing number of Medicaid programs.

Use with: Any ABA CPT code delivered via synchronous audio/video

Payor-specific notes:

  • Aetna, Cigna, UHC, Humana: Accept modifier 95
  • Anthem: Accepts modifier 95 for most plans; verify plan-specific requirements
  • Medicaid: Varies significantly by state (see GT below)

    • GT — Interactive Audio and Video Telecommunication System

    The legacy telehealth modifier still required by some Medicaid programs and a few commercial payors.

    Use with: Any ABA CPT code delivered via synchronous audio/video, when required by the specific payor

    When to use GT vs. 95:

  • If the payor's fee schedule or provider manual specifies GT, use GT
  • If the payor accepts either, use 95 (more universally accepted)
  • Never use both 95 and GT on the same claim line

    • State Medicaid Modifier Requirements

    Several state Medicaid programs require additional modifiers beyond the standard credential-level modifiers:

    StateAdditional ModifierMeaning
    FloridaU1BCBA-supervised services
    TexasU5Telehealth services (instead of GT)
    CaliforniaU1Specific to DHCS ABA billing
    New YorkHHCommunity-based services
    OhioU1BCBA-level supervision

    Always verify current modifier requirements with the state Medicaid fee schedule, as these can change with annual updates.

    The Modifier Matrix

    CPT CodeRBT/BTBCaBABCBATelehealth Add-On
    97151—HNHO+ 95 or GT
    97152HM——+ 95 or GT
    97153HM——+ 95 or GT
    97154HM——+ 95 or GT
    97155—HNHO+ 95 or GT
    97156—HNHO+ 95 or GT
    97157—HNHO+ 95 or GT
    97158—HNHO+ 95 or GT

    Common Modifier Errors

    Error 1: Using HO for RBT services. The most common modifier error. RBTs must bill with HM, not HO. Using HO implies the service was delivered by a master's-level provider, which triggers audits and potential recoupment.

    Error 2: Missing telehealth modifier. Billing telehealth sessions without modifier 95 or GT will result in the claim being processed as an in-person service. If the place of service code (02 or 10) doesn't match the modifier, the claim will deny.

    Error 3: Stacking incompatible modifiers. Some modifier combinations are invalid. For example, you cannot use both HM and HO on the same claim line.

    Error 4: Wrong modifier for the payor. Some payors have non-standard modifier requirements. Always verify modifier requirements in the payor's provider manual before billing.