What the OIG found in ABA Medicaid audits, and how to run your own check
The 30-second answer
Between December 2024 and February 2026, the HHS Office of Inspector General published four state audits in its series on Medicaid ABA payments: Indiana, Wisconsin, Maine and Colorado. In each one, all 100 sampled child-months had improper or potentially improper claim lines, mostly because session notes did not support the code, the units, the signature or the credentials. Estimated improper payments ranged from at least $18.5 million to at least $77.8 million per state. You can run the same check on your own records, one child-month at a time.
Key facts
What the OIG series is
The HHS Office of Inspector General announced its series of Medicaid ABA audits on January 24, 2022. Its stated aim is to determine whether state ABA payments complied with federal and state requirements1. The series has 8 projects: four are completed and four are active, and the titles of projects in progress stay unpublished until their reports are posted1.
The OIG audits states, not individual providers. In Indiana, for example, it asked ABA facilities for the prior authorization, the diagnostic evaluation and referral, the treatment plan and the session notes behind each sampled month2. The State Medicaid Manual, which the OIG cites, makes expenditures allowable only to the extent that adequate, readily reviewable documentation exists when the claim is filed2.
The four published reports
| State and report | Date | Period | Estimated improper payments, at least | Child-months with note or record problems |
|---|---|---|---|---|
| Indiana, A-09-22-02002 | Dec 2024 | 2019 and 2020 | $56.5 million ($39.4 million federal) | 95 of 1002 |
| Wisconsin, A-06-23-01002 | Jul 2025 | 2021 and 2022 | $18.5 million ($12.2 million federal) | 96 of 1003 |
| Maine, A-01-24-00006 | Jan 2026 | 2023 | $45.6 million ($28.7 million federal) | 64 of 1004 |
| Colorado, A-09-24-02004 | Feb 2026 | 2022 and 2023 | $77.8 million ($42.6 million federal) | 93 of 1005 |
Maine’s audit covers rehabilitative and community support services, which for children with autism include ABA and other treatments4. In all four audits, all 100 sampled child-months had improper or potentially improper claim lines2345.
How to read the numbers
- The amounts are estimates. To be conservative, the OIG recommends recovery at the lower limit of a two-sided 90 percent confidence interval, and each headline figure is that lower limit2345.
- Besides the improper payments, each report estimates a larger sum of potentially improper ones: $76.7 million in Indiana, $94.3 million in Wisconsin and $207.4 million in Colorado235. Those are set aside for the state to review.
- The OIG did not review medical necessity in Indiana2.
- The states did not all agree. Wisconsin’s health department disagreed with the main finding on the use of code 971553.
The findings that repeat
- Notes that do not support the code. With 97155 billed, Wisconsin had 75 of 95 months with no sign that an issue was resolved or the protocol changed3. Indiana had 81 months where the notes did not support the code, Colorado 7225.
- Units beyond the documented time. Indiana, 52 months; Colorado, 6325. Causes included nap time, overlapping services and notes signed before the session ended23.
- Signatures. Notes with no signature, signed by someone other than the person who delivered the service, or with electronic signatures that did not meet requirements: 39 months in Indiana and 22 in Colorado25.
- Missing notes. 17 months in Indiana and 26 in Colorado had billed dates with no note25.
- Generic descriptions. Notes that did not say the techniques used, goals or data: 98 months in Indiana, 100 in Wisconsin and 96 in Colorado235.
- Credentials and diagnosis. Staff without the right credentials (26 months in Indiana, 18 in Colorado) and children without the required evaluation or referral (22 in Indiana)25.
On the state side, the OIG found that none of the audited states had done a statewide postpayment review of ABA claims, and that guidance was insufficient26. The OIG noted that a coalition’s industry guidance may have caused confusion about when to bill 971552. In Wisconsin, the state had given no guidance on how to document a protocol change3.
Self-audit list, one child-month at a time
Pick a few child-months, as the OIG does, and compare the claims against the notes. The flags in the CMS toolkit of August 2026 are signals states may use, not rules: CMS says the toolkit creates no new federal requirements7. The list below mixes what the OIG found with those signals.
For the note itself, see what makes a session note hold up.
What is in force and what may change
The OIG series is still open, with four active projects whose titles are unpublished1. No source consulted says whether the OIG has audited or will audit Florida. The toolkit was released on August 4, 2026 and is guidance7.
Each state has its own documentation rules. Florida’s are in its coverage policy8, and the AHCA integrity initiative adds site visits and revalidation. This article is not legal or billing advice: if your check turns up a problem, talk to your plan or an attorney before correcting claims.
Frequently asked questions
Has the OIG audited ABA in Florida?
The published reports cover Indiana, Wisconsin, Maine and Colorado. The OIG series has four more active projects whose titles stay unpublished until the reports are posted, so the series page does not say which states they cover.
Do the OIG audits examine providers or states?
States. Each audit samples one state's fee-for-service payments and asks the ABA facilities for the supporting records. The recommendations are addressed to the state, including refunding the federal share and doing postpayment reviews.
What does improper versus potentially improper mean?
Improper payments are those the OIG found did not meet requirements, such as notes that did not support the code billed. Potentially improper ones are set aside for the state to resolve because the documentation was not detailed enough or looked unreliable.
Is the CMS toolkit a new federal rule for ABA providers?
No. CMS says the toolkit does not establish new federal requirements. It is a resource for state Medicaid and CHIP agencies, and its list of documentation flags shows what states may look at.
Sources
- Audits of Medicaid Applied Behavior Analysis for Children Diagnosed With Autism (series SRS-A-25-029). HHS Office of Inspector General (OIG), work plan, last modified Feb 25, 2026.
- Indiana Made at Least $56 Million in Improper Fee-for-Service Medicaid Payments for Applied Behavior Analysis (A-09-22-02002). HHS Office of Inspector General (OIG), December 2024.
- Wisconsin Made at Least $18.5 Million in Improper Fee-for-Service Medicaid Payments for Applied Behavior Analysis (A-06-23-01002). HHS Office of Inspector General (OIG), July 2025.
- Maine Made at Least $45.6 Million in Improper Fee-for-Service Medicaid Payments for Rehabilitative and Community Support Services (A-01-24-00006). HHS Office of Inspector General (OIG), January 2026.
- Colorado Made at Least $77.8 Million in Improper Fee-for-Service Medicaid Payments for Applied Behavior Analysis (A-09-24-02004). HHS Office of Inspector General (OIG), February 2026.
- State Medicaid & CHIP Applied Behavior Analysis Toolkit. Centers for Medicare & Medicaid Services (CMS), copy hosted by AHCA, August 2026.
- CMS Launches New State Toolkit to Protect Children with Autism, Strengthen Oversight of Applied Behavior Analysis Services. Centers for Medicare & Medicaid Services (CMS), Aug 4, 2026.
- Florida Medicaid Behavior Analysis Services Coverage Policy. Agency for Health Care Administration (AHCA), December 2024, rule 59G-4.125.