ABA Therapy Billing 101: Codes, Auths & Denials

In 2019, the American Medical Association (AMA) CPT Editorial Panel converted temporary Category III tracking codes into permanent Category I CPT codes for adaptive behavior services.

Almost every ABA code is billed in 15-minute increments. You have to match the right provider credential to the right code, or the claim kicks back immediately.

It’s important to record session minutes accurately. Payers follow time rules from the Centers for Medicare & Medicaid Services (CMS). If your session times don’t match the units on your claim form, you could fail an audit.

You cannot bill any ABA services without an approved authorization on file. ABA authorizations work in two distinct phases:

Treatment authorizations are usually approved for a period of six months. In order to ensure that your ongoing treatment plans are approved without delay, it is important that the packet includes:

• Scores obtained from established tools such as the VB-MAPP, ABLLS-R, AFLS, or Vineland-3.
• Behavioral goals that are measurable and have specific targets for reduction together with clear criteria for mastery.
• If the treatment plan doesn’t contain parent training or states that the parents have refused to take part, many commercial payers will cut back on the direct 1:1 hours that have been approved.
• A clear discharge plan outlining how hours will fade as the child meets goals.

Concurrent billing happens when a BCBA provides protocol modification (97155) in the same room where an RBT is running direct therapy (97153).

Both providers are working with the same child at the same time. How do you bill for that?

You also need to comply with the Behavior Analyst Certification Board (BACB), which means that RBTs must have direct supervision for at least 5% of their total monthly ABA delivery hours. If your billing arrangement causes you to omit the documentation of supervision due to billing confusion, then both your certifications and your income are put at risk.

Because ABA clinics employ multiple tiers of providers (BCBA-D, BCBA, BCaBA, and RBT), claims must clearly communicate who delivered each unit of service. Payers use specific modifiers to determine reimbursement rates and verify provider qualifications:

• Modifier HO: Master’s degree level (applied to BCBAs).
• Modifier HN: Bachelor’s degree level (applied to BCaBAs or mid-tier supervisors).
• Modifier HM: High school level / less than Bachelor’s (commonly applied to RBTs and line therapists).
• Modifier HP: Doctoral level (applied to BCBA-Ds or licensed clinical psychologists).
• Modifier 95: Synchronous telehealth service (used when parent guidance via 97156 or remote supervision is approved for virtual delivery).

Always confirm whether a payer requires the billing NPI to be the group practice (Box 33a on the CMS-1500) while the individual RBT or supervising BCBA appears as the rendering provider (Box 24J).

To keep days in accounts receivable (A/R) below 35, ABA practices should establish a strict, repeatable revenue cycle routine:

• Audit Diagnoses Early: Confirm that the child’s ASD diagnosis meets specific payer requirements and contains clear ICD-10 coding from an authorized medical evaluator.
• Track Units Weekly: Do not wait until month-end to check authorization pools. Run weekly utilization reports to prevent technicians from exhausting hours before the authorization cycle ends.
• Make sure that technicians and BCBAs complete, sign, and seal the session notes within 24 hours; if the clinical notes are delayed then the billing batches will be delayed and this will cause cash flow problems.
• Audit Overlapping Timestamps: Ensure your scheduling software prevents technicians and supervisors from accidentally entering overlapping time slots that violate payer rules.