Medicaid ABA audits: what OIG found and how small agencies can get audit-ready

Federal audits of Medicaid ABA payments have become a steady series. Since late 2024, the federal Office of Inspector General (OIG) has published audit reports on Medicaid ABA payments in four states, and more are underway. For a small agency, that can sound alarming. We see it differently: the reports are a free, public guide to exactly what auditors look for, and an agency that runs to that standard is simply a better-run agency.

This article walks through what OIG found, what the findings have in common, and a practical audit-readiness checklist for owners of small and mid-size ABA agencies. It’s general information, not legal or billing advice, and every state’s rules differ, so check yours.

Where the Medicaid ABA audit series stands

OIG runs these reviews as one series, “Audits of Medicaid Applied Behavior Analysis for Children Diagnosed With Autism.” Its series page lists eight projects. Four are complete: Indiana (December 2024), Wisconsin (July 2025), Maine (January 2026) and Colorado (February 2026). The other four are listed as active, with titles unpublished until the reports post.¹

The completed audits reviewed each state’s fee-for-service Medicaid payments for ABA. The headline findings:

• Indiana: at least $56 million in improper fee-for-service payments for ABA in 2019 and 2020. OIG recommended the state refund $39.4 million, the federal share.²
• Wisconsin: at least $18.5 million in improper payments for ABA in 2021 and 2022, with a recommended federal refund of $12.2 million.³
• Maine: at least $45.6 million in improper payments for rehabilitative and community support services for children with autism, which in Maine include ABA.⁴
• Colorado: at least $77.8 million in improper payments for ABA in 2022 and 2023, with a recommended federal refund of $42.6 million.⁵

In Indiana, Wisconsin and Colorado, OIG reviewed a sample of 100 enrollee-months, and in each state all 100 included at least one claim line that was improper or potentially improper.^2,3,5 These audits are addressed to state Medicaid agencies, not to individual providers. But the claims in those samples were agencies’ claims, and OIG also recommended that states run their own periodic postpayment reviews of ABA claims, to educate providers and recover payments that didn’t meet requirements.^2,3,5 That’s the part that reaches agencies directly.

What the OIG ABA audits have in common

Read the recommendations side by side and the same handful of themes appear. Almost none of them are about the quality of care. They’re about whether the paperwork proves the service that was billed.

• Session notes that don’t support the claim. OIG asked Indiana, Wisconsin and Colorado to give providers more guidance on the detail session notes need to support the ABA billed.^2,3,5 In Maine, OIG found session notes that lacked a full description of the services provided, the goals addressed or the data collected.⁴
• Signatures. State signature requirements come up in Indiana, Wisconsin and Colorado.^2,3,5 In Maine, some required assessments were missing the signatures of the staff who conducted them or of the parents or guardians.⁴
• What counts as billable time. Indiana, Wisconsin and Colorado were each asked to clarify what the state considers billable ABA time.^2,3,5
• Supervision codes. The reports single out the documentation needed to support CPT 97155 (and, in Indiana, 97156).^2,3,5
• Who rendered the service. OIG recommended Wisconsin verify which provider rendered 97153 services and pay based on that provider’s level, and Colorado was asked to give guidance on credentialing requirements.^3,5
• The front-end file. In Indiana and Colorado, OIG asked the states to check how their prior authorization contractors verify diagnostic evaluations and treatment referrals.^2,5 In Maine, some services went to children who had not received the required assessment.⁴

The good news for a small agency: every item on that list is an operations habit, not a mystery. You can fix it this quarter.

An audit-readiness checklist for small ABA agencies

Here’s the routine we’d put in place. It assumes you already have a practice-management or billing system; the point is the habits around it.

1. Write your own “billable time” rule. Pull your state Medicaid ABA manual and each managed care plan’s policy, and write one page for your team on what is and isn’t billable: setup, travel, cancellations, note-writing, overlapping sessions. Train new staff on it in week one.
2. Make notes complete before they’re billable. Set up your system so a session can’t move to billing until the note has the required fields and signatures. That one rule addresses several of the findings above.
3. Treat 97155 and 97156 as their own category. Make sure the note for every supervision or caregiver-guidance unit shows what was done, in the terms your state requires. The OIG reports singled these codes out.
4. Match the rendering provider to the claim. Check that the person on the claim is the person in the note, and that their credential, enrollment and payer credentialing were active on the date of service.
5. Keep a complete intake file for every client. Diagnostic evaluation, referral, assessment, authorization and consent forms, signed and dated, in one place before services start. A short intake checklist does most of the work.
6. Run a monthly self-audit. Pull a small random sample of claims, around ten, and check each against its note, signatures, authorization and rendering provider. Fix the pattern, not just the claim. If you find money you shouldn’t have been paid, talk to a healthcare attorney about how to return it.
7. Know what you’d hand over. If a records request arrived tomorrow, who would pull the files, and how fast? Practice once, before you have to.

Most of this overlaps with good revenue habits. If you haven’t yet, read authorized, delivered, billed: where ABA revenue quietly leaks and our guide to ABA claim denials and cash flow. The same clean documentation that holds up in an audit also gets claims paid the first time.

Why audit readiness is worth it, even if you’re never audited

For a small agency, a single payback demand can strain cash flow for months. But the bigger payoff of audit readiness shows up every day:

• Fewer denials and faster payment, because claims go out right the first time.
• Less dependence on one person who “just knows” how billing works.
• A stronger position with partners and buyers. Anyone looking closely at an agency will look at its documentation and billing. If you’re thinking about your next stage, see how to prepare your ABA agency for sale.
• Peace of mind. Knowing your files would hold up frees you to focus on growth.

How Anchor helps agencies tighten compliance and billing

We’ve built and run ABA agencies ourselves, across 13+ states and many different payers, so we know how these rules show up in day-to-day operations. We work with owners in three ways:

• Advisory. On a monthly retainer, we work alongside you from the outside: clear KPIs and visibility into your operation, tight workflows, and practical help with intake, authorizations, utilization, billing and collections.
• Partner. For established agencies ready to grow: growth capital from $250K to $1M+, plus an experienced operator at your side who works within your systems and with your vendors. You run the agency.
• M&A. For owners ready to explore the next chapter, confidentially, whether that means stepping back or weighing options.

We’re not your attorney or your billing auditor, and we’ll tell you when you need one. What we bring is the operating side: systems, workflows and the discipline to keep them running. Read why we partner with established ABA agencies, see how a conversation with us works, or write to us at hello@anchorhcp.com. Every conversation is confidential.

Sources

Reports and pages as published on the dates shown. Federal, state and payer requirements change; check your state Medicaid manual, your payer agreements and your own legal and billing advisors before relying on them.

1. HHS Office of Inspector General, Work Plan series SRS-A-25-029: Audits of Medicaid Applied Behavior Analysis for Children Diagnosed With Autism (read November 3, 2026).
2. HHS Office of Inspector General, Indiana Made at Least $56 Million in Improper Fee-for-Service Medicaid Payments for Applied Behavior Analysis Provided to Children Diagnosed With Autism (A-09-22-02002) (issued December 16, 2024).
3. HHS Office of Inspector General, Wisconsin Made at Least $18.5 Million in Improper Fee-for-Service Medicaid Payments for Applied Behavior Analysis Provided to Children Diagnosed With Autism (A-06-23-01002) (issued July 10, 2025).
4. HHS Office of Inspector General, HHS-OIG Audit Finds Maine Made At Least $45.6 Million in Improper Medicaid Payments for Autism Services (report A-01-24-00006) (report completed January 16, 2026).
5. HHS Office of Inspector General, Colorado Made at Least $77.8 Million in Improper Fee-for-Service Medicaid Payments for Applied Behavior Analysis Provided to Children (A-09-24-02004) (issued February 25, 2026).