Why ABA Has a Higher Denial Rate Than Other Specialties

ABA billing has a structurally higher denial rate than most other healthcare specialties for several reasons:

  • Complex authorization requirements — ABA requires prior authorization from virtually every payor, with payor-specific documentation requirements
  • High unit volume — ABA clients often receive 20–40 hours per week of services, creating more billing opportunities for errors
  • Multiple provider types — Claims involve BCBAs, BCaBAs, and RBTs with different modifier requirements
  • Frequent policy changes — Payor ABA policies change more frequently than most specialty policies

    • The average ABA practice has a denial rate of 8–15%. Best-in-class practices achieve 3–5%. Here are the ten most common denial reasons and how to address them.

    Denial #1: Authorization Not on File

    Frequency: Most common denial reason across all payors

    Cause: The claim was submitted for a date of service that falls outside the authorization period, or the authorization was not obtained before services began.

    Prevention:

  • Verify authorization status before every session, not just at intake
  • Set up automated alerts in your practice management system for authorizations expiring within 30 days
  • Implement a "no auth, no service" policy for new clients

    • Recovery: If services were rendered without authorization, file a retro-authorization request immediately. Most payors have a 30-day window for retro-auth requests.

    Denial #2: Exceeds Authorized Units

    Frequency: Second most common denial

    Cause: The claim bills more units than were authorized, either because the authorization was not tracked correctly or because the client received more services than authorized.

    Prevention:

  • Configure your practice management system to track remaining authorized units in real-time
  • For Anthem clients specifically, configure weekly unit tracking (not total authorization tracking)
  • Implement a workflow to notify schedulers when a client is within 10% of their authorized unit limit

    • Recovery: File a concurrent review request with the payor to request additional authorized units. Include updated progress notes showing clinical need.

    Denial #3: Missing or Incorrect Modifier

    Frequency: Third most common denial

    Cause: The wrong credential-level modifier (HM, HN, HO) was used, or the telehealth modifier (95 or GT) was missing for telehealth sessions.

    Prevention:

  • Create a modifier matrix for each provider type in your practice
  • Configure your billing system to automatically apply the correct modifier based on the rendering provider's credential level
  • Audit claims monthly for modifier accuracy

    • Recovery: File a corrected claim with the correct modifier. Most payors accept corrected claims within 365 days of the original date of service.

    Denial #4: Diagnosis Code Mismatch

    Frequency: Fourth most common denial

    Cause: The ICD-10 diagnosis code on the claim does not match the diagnosis code on the authorization, or the diagnosis code is not covered for ABA services.

    Prevention:

  • Verify that the diagnosis code on the claim exactly matches the authorization
  • ABA services are covered for ASD diagnoses (F84.0, F84.1, F84.3, F84.5, F84.8, F84.9) — not for related conditions like speech delay or intellectual disability alone
  • When a client has multiple diagnoses, list the ASD diagnosis first

    • Recovery: File a corrected claim with the correct diagnosis code. If the original authorization was issued with the wrong diagnosis code, contact the payor to correct the authorization record.

    Denial #5: Timely Filing Exceeded

    Frequency: Fifth most common denial, and the most difficult to recover from

    Cause: The claim was submitted after the payor's timely filing deadline.

    Timely filing limits by payor:

  • Aetna: 180 days
  • Anthem: 90–365 days (varies by plan)
  • Cigna: 90 days
  • UHC: 90–365 days (varies by plan)
  • Medicaid: 12 months (most states)

    • Prevention:

  • Submit claims within 30 days of the date of service
  • Monitor your claim submission queue daily for claims that have not been submitted
  • Set up automated alerts for claims approaching the timely filing deadline

    • Recovery: Timely filing denials are very difficult to overturn. Document any extenuating circumstances (system outages, natural disasters, payor portal issues) and file an appeal with supporting documentation.

    Denial #6: Provider Not Credentialed

    Frequency: Sixth most common denial

    Cause: The rendering provider (BCBA or RBT) is not credentialed with the payor, or the credentialing is pending.

    Prevention:

  • Begin credentialing new providers immediately upon hire — the process takes 90–120 days
  • Maintain a credentialing status tracker for all providers
  • Do not schedule new clients with providers who are not yet credentialed

    • Recovery: File an appeal with documentation of the credentialing application and the date it was submitted. Some payors will retroactively process claims once credentialing is complete.

    Denial #7: Duplicate Claim

    Frequency: Seventh most common denial

    Cause: The same claim was submitted twice, either due to a system error or a manual resubmission after an initial submission was not received.

    Prevention:

  • Implement claim submission tracking to prevent duplicate submissions
  • When resubmitting a claim, always void the original claim first

    • Recovery: Identify which submission was processed and void the duplicate.

    Denial #8: Place of Service Mismatch

    Frequency: Eighth most common denial

    Cause: The place of service code on the claim does not match the actual location where services were rendered, or the payor does not cover ABA at the billed place of service.

    Prevention:

  • Verify that the payor covers ABA at the place of service where the client receives services (home, clinic, school)
  • For telehealth, use POS 10 (patient's home) when the client is at home, not POS 02

    • Recovery: File a corrected claim with the correct place of service code.

    Denial #9: Missing Documentation

    Frequency: Ninth most common denial (more common for audits than initial submissions)

    Cause: The payor requests documentation to support the claim and the practice cannot produce it within the required timeframe.

    Prevention:

  • Maintain session notes, authorization records, and treatment plans in a centralized, easily accessible location
  • Implement a documentation audit process to verify that all required documentation is complete before billing

    • Recovery: Respond to documentation requests within the payor's specified timeframe (typically 30–45 days). Incomplete responses result in automatic denials.

    Denial #10: Coordination of Benefits Issue

    Frequency: Tenth most common denial

    Cause: The client has secondary insurance and the primary payor has not yet processed the claim, or the coordination of benefits information is incorrect.

    Prevention:

  • Verify coordination of benefits at intake and at each authorization renewal
  • Submit to the primary payor first and wait for the Explanation of Benefits before submitting to the secondary payor

    • Recovery: Obtain the primary payor's EOB and submit to the secondary payor with the EOB attached.