ABA Billing and CPT Codes in 2026: The Complete Sourced Reference (and What Changes January 1, 2027)

On January 1, 2027, the code set your entire revenue cycle runs on stops existing in its current form. The AMA CPT Editorial Panel approved six new Category I codes, a revision of every code from 97151 through 97158, revised guidelines for how the set is used, and the deletion of the temporary T codes (0362T and 0373T). It was decided at the Panel’s September 2025 meeting.

Here is the strange part, and the reason this page exists: nobody is allowed to tell you what the new codes say. The descriptors are under the AMA’s CPT confidentiality agreement until the 2027 CPT Professional Code Book publishes in late 2026. The organizations that wrote the applications are legally barred from describing their own work.

That gap — a confirmed, field-wide billing change that no one can legally detail for another few months — is exactly the kind of vacuum that fills with confident nonsense. It is already starting.

So this page draws hard lines. It gives you every current ABA code with its official descriptor, separates what is confirmed about 2027 from what is speculation, and lays out what the real federal data says about denials and prior authorization — from the HHS Inspector General, the AMA, and KFF, not from billing vendors. Where a number does not exist in citable form — and one very popular number does not — we say that instead of inventing it.

What is actually confirmed about the 2027 overhaul

You do not have to take a vendor’s word for any of this. It is in the AMA’s own public document: the September 2025 CPT Editorial Panel Summary of Panel Actions, Tab 56, “Adaptive Behavior Services Revisions.” The six new codes appear there under placeholder numbers (97X1X through 97X6X) — placeholders are how the AMA lists accepted codes whose descriptors are still embargoed. It is corroborated by the organizations that filed the applications: the ABA Coding Coalition, the Association of Professional Behavior Analysts, and the Virginia Association for Behavior Analysis.

6 new codes

The Panel accepted the addition of six new Category I CPT codes for adaptive behavior services. Category I matters: these are permanent, standard codes, not temporary tracking codes.

97151–97158

All eight existing Category I codes are being revised, along with the guidelines governing how the set is used.

T codes deleted

0362T and 0373T — the two surviving Category III codes, used for the two-technician, QHP-on-site scenarios — are being deleted outright.

Jan 1, 2027

Effective date. The 2027 CPT Professional Code Book, which will contain the actual descriptors, publishes in late 2026.

Sept 2025

The AMA CPT Editorial Panel meeting where this was approved. This has been settled for roughly ten months, which is worth knowing if it is news to you.

Read the shape of that and you can infer the direction without guessing at the language. Every ABA service code becomes permanent Category I. The temporary codes go away. The set grows from ten codes to fourteen. A field whose billing has been partly stuck in Category III purgatory since 2014 is getting a fully permanent code set — and Category III codes are the ones payers most often treat as investigational and decline to price.

What you cannot know yet: the exact descriptors, the time units, the supervision requirements, which services the six new codes cover, and how the revisions change what you are doing today with 97153 and 97155. Anyone telling you those specifics right now is guessing.

The current ABA code set, with official descriptors

Until January 1, 2027, this is the set. A note on what follows: the official CPT descriptors are copyrighted by the AMA, and reproducing them in full generally requires a license. So the summaries below are ours, not the AMA’s wording. The structural facts — which code, who performs it, the time unit, whether the QHP must be present — are facts, and they are verified against the ABA Coding Coalition’s official supplemental guidance. For the verbatim descriptors, go to that document or the CPT code book.

The thing to internalize: every code in this set is a 15-minute timed code. There are no per-hour codes, no per-day codes, and since 2019 no “first 30 minutes plus add-on” codes. That is the most common misconception in ABA billing.

Assessment codes.

Treatment codes.

Three rules that cause more denials than any coding error. Supervision without the patient present is not billable — that is an indirect service, and CPT has no stand-alone code for it. Ongoing treatment planning is bundled into the direct service codes. And indirect services have no CPT code at all unless your payer allows a HCPCS workaround. If your model assumes you can bill for team meetings or planning time, the code set disagrees.

On concurrent billing, the rule people get wrong: 97153 and 97155 can be billed at the same time, but not by the same person. The Coalition is explicit that a single QHP may not report both concurrently. It requires two people — technician delivering, QHP directing, both face-to-face with the patient. Also settled: 97154 and 97158 cannot be billed together, and 0373T cannot be billed with 97155 because directing the technician is already bundled into 0373T’s on-site requirement.

Two pieces of history worth knowing, because they explain why 2027 matters. This set only became permanent Category I on January 1, 2019. Before that, ABA billed entirely through temporary Category III codes (the 0359T–0374T family) introduced July 1, 2014 — codes payers could and did refuse to price. The 2019 transition deleted fourteen of those codes, converted untimed codes to 15-minute units, abolished the 30-minute-plus-add-on structure, and left 0362T and 0373T behind as Category III strays. The 2027 change finally cleans that up: the strays are deleted and everything lives in Category I.

And to answer the question that brings most people here: there were no CPT descriptor revisions in 2025 or 2026. The 2019 descriptors have been in force this entire time. Everything is happening on January 1, 2027.

Denials and prior authorization, by the numbers

Start with the thing nobody in this industry will tell you, because it is bad for business: there is no citable ABA-specific claim denial rate. It does not exist. Every “ABA denial rates run 10–30%” claim you have read traces to a vendor blog citing another vendor blog. The federal transparency data that produces real denial rates cannot be broken out by service — KFF, whose analysis is the gold standard, says so explicitly: because the data do not link denial reasons to the services denied, neither the share denied for a given reason nor the service most often denied can be calculated.

So anyone quoting you an ABA denial rate sourced to KFF is fabricating. What follows is real data that is either all-payer or behavioral-health-wide, labeled as such. It is less satisfying than a made-up number and considerably more useful.

The first federal audit of behavioral health denials landed six weeks ago, and it is damning.

100 of 100

Sampled denied behavioral health prior authorization requests that failed to meet all requirements, in an HHS Office of Inspector General audit of a Pennsylvania Medicaid managed care organization. A 0% compliance rate. The OIG notes this is its first audit ever to review behavioral health service denials — issued June 8, 2026. Report A-03-24-00204. One MCO, one state — do not generalize it to your payer. Do notice that the first time anyone federal looked, every single denial was out of compliance.

1 in 8

Prior authorization requests denied by Medicaid managed care organizations, across 115 MCOs covering 29.8 million enrollees. Twelve of those MCOs denied over 25% — twice the overall rate. HHS OIG, 2019 data.

95% / 18%

Share of appealed Medicare Advantage prior-auth denials that were overturned, versus the share of denials that were actually appealed. HHS OIG, June 2026. This is skilled nursing facility admissions, not ABA — but it is the clearest evidence anywhere that denials are frequently wrong and rarely challenged.

Now the appeal math, which is the part most clinics get wrong. Across ACA marketplace plans, fewer than 1% of denied claims are ever appealed — and when they are, insurers uphold their own denial 66% of the time, meaning roughly a third get overturned. Only 40% of consumers even know they have the right to appeal. KFF, 2024 data.

19%

In-network claim denial rate across HealthCare.gov issuers in 2024, from 451 million in-network claims across 157 insurers. Out-of-network runs 37%. Note the scope: marketplace plans only — not employer plans, not Medicaid, not Medicare. The famous “insurers deny 1 in 5 claims” line comes from here, and the qualifier gets dropped constantly.

3% – 36%

The spread in in-network denial rates between individual insurers in the same year. A twelve-fold difference. Which payer you contract with matters more than almost anything you do operationally.

36%

Share of in-network denials whose stated reason was “other” — no reason disclosed. The single largest category. Medical necessity, which is what everyone builds their appeals strategy around, accounts for 5%.

Prior authorization is the tax underneath all of it. The AMA’s 2025 physician survey (n=1,000, fielded December 2025) is the best measurement of the burden, and Medicaid — where most ABA volume lives — sits near the top.

40 / 13 hrs

Prior authorizations per physician per week, and physician-plus-staff hours per week spent on them. 40% of practices have staff working exclusively on prior auth. AMA, 2025.

59%

Physicians who do not appeal adverse PA decisions because they do not believe an appeal will succeed; another 52% cite insufficient staff or time. Set that next to the OIG’s 95%-overturn finding. The belief that appeals do not work is itself the most expensive thing in the revenue cycle.

26%

Physicians reporting that prior authorization led to a serious adverse event for a patient; 8% report it contributed to disability, permanent damage, or death. Note this is “more than 1 in 4” — if you have seen “1 in 3,” that is the stale 2021 figure.

95% / 79%

Physicians reporting PA delays necessary care, and physicians reporting PA can at least sometimes lead to treatment abandonment. Read that second one carefully: it is a share of physicians reporting, not a share of patients who abandon treatment. It is mangled into the latter constantly.

Finally, the one genuinely ABA-specific, actionable billing finding in the peer-reviewed literature — and the real answer to “what is my per-day unit limit.” It is not a payer policy. It is the Medically Unlikely Edit, and we pulled the current values straight from CMS’s practitioner MUE table effective July 1, 2026.

8 units

Medicare’s MUE for 97151 — two hours per day. The tightest limit in the set, and the one the ABA Coding Coalition is actively lobbying CMS to raise.

32 / 24 units

Medicare’s MUE for 97153 (8 hours) and 97155 (6 hours). For the rest: 97152, 97156, 97157, 97158 and 0362T are 16 units; 97154 is 18; 0373T is 24.

Not a benefit limit

CMS defines an MUE as the maximum units reported on the vast majority of appropriately reported claims — not a cap on what is medically necessary. Kornack, Unumb, and Williams, in Behavior Analysis in Practice, document payers misusing MUEs as hard limits and denying ABA on that basis.

Here is the actionable part. Medicaid MUEs differ from Medicare MUEs, and Medicaid’s are the clinically appropriate ones for ABA — the typical ABA patient is a child, not a Medicare beneficiary. Kornack et al. reported Medicaid’s 97151 MUE at 32 units against Medicare’s 8 (as of 2023 — we could not re-verify the current Medicaid value, because the CMS dataset the Coalition links to is dead). Yet commercial payers routinely adopt the stricter Medicare edit. If your 97151 claims are getting chopped at two hours, that is a concrete, checkable thing to raise with your payer.

That paper is also, as far as we can find, essentially the only peer-reviewed literature on ABA insurance denials. A field billing billions of dollars a year has one study. That is not a gap in our research; it is a gap in the evidence base, and it is why the vendor blogs have had such an easy time filling it.

Worth knowing where the limits do not come from: no major commercial payer publishes per-day or per-week CPT unit caps for ABA. We went through Aetna’s medical necessity guide, Cigna/Evernorth policy EN0499, Optum’s ABA FAQ, and Anthem’s state provider guides. The unit-limit tables circulating on billing-vendor blogs, attributed to these payers, are not in these payers’ documents. What the payers actually publish is supervision ratios — Optum expects about 2 hours of QHP direction per 10 hours of technician time, Aetna and Cigna 1 to 2 hours per 10. That is the real constraint on your staffing model, and it is nowhere near as widely discussed as the fake unit caps.

The audit nobody in ABA is talking about, and probably should be

Everything above is about money payers keep from you. This is the opposite: money the federal government is trying to take back, and it is the most ABA-specific data in this entire article.

HHS OIG is running an audit series on Medicaid ABA payments, announced in January 2022 and running through FY2027. Four states are published so far. In all four, the finding is the same sentence: all 100 sampled enrollee-months included payments for one or more claim lines that were improper or potentially improper. One hundred out of one hundred. Four times.

$56M

Improper fee-for-service Medicaid ABA payments in Indiana (2019–2020), with a $39.4M federal refund recommended. In 97 of 100 sampled months, services were rendered by staff without appropriate credentials.

$18.5M

Wisconsin (2021–2022). Top two causes: session notes that did not support the CPT code billed, and session notes that did not support the number of units billed.

$45.6M

Maine (2019–2023), $28.7M federal refund recommended.

$77.8M

Colorado (2022–2023), issued February 2026. Documentation failures concentrated in 97155, plus uncredentialed behavior technicians. Colorado’s FFS Medicaid ABA spending had grown from $60.1M in 2019 to $163.5M in 2023.

Read the root causes rather than the dollar figures, because the root causes are a checklist for your own documentation. Session notes that do not justify the code billed. Session notes that do not justify the units billed. Staff without the credentials the code requires. Missing signatures. No documentation of protocol changes. Nothing exotic — it is the ordinary stuff, at scale, in every state examined.

Two fairness notes. The OIG’s framing is contested: the ABA Coding Coalition met with OIG in September 2025 to address what it called misunderstandings evident in the Indiana and Wisconsin reports, and OIG agreed to present at APBA and CASP conferences. And be careful with the Colorado number — some coverage reported “$285.2 million,” which aggregates improper and potentially-improper federal-share figures. OIG’s own headline is “at least $77.8 million.” Use OIG’s.

Billing statistics that are wrong, stale, or mangled

Same disease as the workforce numbers, different organ. These are all in current circulation.

Two numbers we went looking for and could not responsibly publish, which we mention because their absence is itself information. There is no citable figure for the share of a therapy clinic’s revenue lost to denials and underpayment — every version traces to vendor marketing. And the MGMA benchmarks everyone quotes for days in A/R and clean claim rate (“35 days,” “top quartile under 5%”) could not be verified against MGMA’s actual paywalled report; every instance we found was a billing company restating them without attribution. We would rather leave a hole than fill it with something we cannot stand behind.

What this means for your clinic

Billing is where a rate cut becomes real. When reimbursement per unit falls — and it is falling in the states with the most volume, as we covered in A Rate Cut Is Not a Margin Problem — the two levers left are collecting more of what you have already earned, and serving more families. The first is a billing problem. The second is a demand problem, and it is the one most clinics leave untouched.

Citing this page

Suggested citation: ABA Clinic Marketing, “ABA Billing and CPT Codes in 2026: The Complete Sourced Reference,” July 16, 2026, abaclinicmarketing.com/blog/aba-billing-cpt-codes-2026. Code descriptors belong to the AMA and are reproduced here for reference; cite the ABA Coding Coalition for the code set itself.

We will update this page when the 2027 descriptors publish and the confidentiality period ends. If you spot an error, tell us and we will fix it and say so.