ABA Authorizations and Units: Track 97151-97158 So Sessions Get Paid

An ABA approval is a unit budget with three parts: which codes it covers, how many 15-minute units it allows and the period it runs. Payers can set all three differently.

That last point matters more than it sounds. Two clients with the same hours can sit under two very different approvals. One payer approves units for a group of codes. Another writes one monthly number keyed to a single code. A third asks for hours per week. If your tracking assumes one structure for everyone, the math breaks the first time a payer does it differently.

Here is how four payers describe their structure in their own documents. These are examples, not a list of every option.

Read the approval letter for five things

Before you log an approval, pull out:

• the codes or clusters it covers
• the number of units or hours
• whether the period is a week, a month or the whole authorization span
• the start and end dates
• any limit on who can render the service or where

Approval letters don't all look alike, so treat this as a reading list for your team, not a list of fields every payer prints. If the letter leaves one of these out, ask the payer before the first session rather than after the first denial.

Every code from 97151 to 97158 is reported per 15 minutes. But assessment and treatment codes are authorized and capped differently.

The CPT descriptors for the whole family are written "each 15 minutes" (CMS CY 2027 PFS proposed rule, §(47)). Evernorth's provider guide says the same thing in plain words: "All of the ABA CPT codes are in 15-minute increments" (Evernorth autism resource guide). What differs is whether the code needs an authorization at all and how many units Medicare's edits allow in a day.

MUE values come from the CMS Medicare NCCI practitioner MUE table for Oct 1 to Dec 31, 2026. Each one is a date-of-service edit. Prior-auth sources: Optum Q1, Evernorth PA form, Virginia DMAS.

Medicaid is its own question. CMS publishes a separate Medicaid MUE file. For this quarter its values for 97151–97158 match Medicare's except that 97151 is 32. The file header also says it "should NOT be used by state Medicaid programs as their edit file" (CMS Medicaid NCCI edit files). So for Medicaid clients check your state's own limits.

This post only covers how each code is counted. For who can render each code, modifiers and the common denials, see our ABA therapy billing 101 guide.

Four 15-minute units make one hour of a single code. How a partial unit rounds is set by the payer, so check each contract.

Hours to units

The math for full hours is simple. Weekly hours × 4 = weekly units for one code. Monthly approvals add a step. Evernorth multiplies the hours requested per week by 4.33 "to determine monthly averages" (Evernorth PA form).

Illustrative example (not a payer rule): a client approved for 20 hours a week of 97153 has 80 units a week. Under Evernorth's monthly conversion that's 20 × 4.33 = 86.6 hours, or about 346 units a month. Round the way your approval letter does. Don't assume.

Do the math for each code or cluster on its own. Twenty hours of 97153 and two hours of 97155 are two separate lines unless the payer approves them as one pool.

Partial units

We found no national rule for rounding a partial ABA unit in the CMS and payer sources we checked. The best-known minute table, 8 to 22 minutes for one unit, sits in Medicare's Claims Processing Manual chapter for Part B outpatient rehabilitation and CORF services (CMS Claims Processing Manual ch. 5, §20.2). It's written for those services, not for ABA.

Payers set their own position. Optum is a good example. Some of its commercial ABA fee schedules may have carried a footer saying 10 minutes or more must be provided to bill a unit. Optum says that footer "is a recommendation for record-keeping purposes, and not a formal requirement" and that claims should be "consistent with CMS billing and coding guidelines" (Optum ABA CPT FAQ, Q36). Read your contract and fee schedule before you build session templates around a minute threshold.

Daily caps

A medically unlikely edit (MUE) is the most units of a code that the same provider reports for the same beneficiary on the same date of service on the vast majority of correct claims. Medicare contractors use MUEs to reduce improper payments (CMS MUE page). For 97153 that's 32 units a day, or eight hours.

Commercial plans can use them too. Optum says "For our commercial ABA program MUE's apply." It also allows 32 units a day of 97151 so assessments can run in longer sessions (Optum ABA CPT FAQ, Q50–Q51). Long assessment days and full-day intensive schedules are where daily caps bite, so check them when you schedule, not when you bill.

When two providers bill the same minutes

Concurrent billing changes the ledger. Evernorth says only one provider can bill for a unit of time, with an exception for 97153, 97154 and 97155 when the BCBA directs the technician and both are face to face with the patient (Evernorth autism resource guide). Optum allows 97153 and 97155 to be billed concurrently when supervision happens (Optum ABA CPT FAQ, Q16).

Where it's allowed, both providers bill units for the same minutes and both draw on what was approved. One supervised hour can use four units of 97153 and four of 97155. Log both. Also note what can't overlap. Evernorth policy EN0499 says ABA isn't covered "at the same time as any other treatment modality", for example ABA and speech therapy (Evernorth EN0499).

Track every authorization as its own line and compare four numbers each week: approved, scheduled, delivered and billed.

A unit ledger is a running record of each approval and what has been used against it. It can live in your practice management system or a spreadsheet. What matters is that it's current and that everyone who schedules or bills reads the same one.

The two formulas

Remaining = approved − billed − delivered but not yet billed − scheduled through the end date.

Pace = units used ÷ (approved × days elapsed ÷ days in the period).

A pace over 100% means the client will run out before the end date at the current schedule. A pace well under 100% means hours were approved but not delivered. That can come up when you ask to continue, so note the reason, like illness or a school break, while you still remember it.

If you want an early warning, pick your own trigger, for example a pace of 110% for two weeks running. That's your own internal setting, not a payer standard.

Match the ledger to the payer's structure

Build the line the way the approval is written. For example:

• Optum: one line per cluster, since units can shift inside a cluster.
• Evernorth: one monthly line keyed to 97155, with the treatment codes drawing from it.
• Aetna: weekly hours for treatment codes and an auth-period total for assessment codes.
• Virginia Medicaid: one line per treatment code.

A ledger built per code for a payer that approves by cluster can show false shortfalls. A ledger built as one pool for a payer that approves per code can hide real ones.

Reconcile every week

Each week, match three things. Scheduled sessions should match session notes. Notes should match claims. Claims should match remits. Session notes do the most work here. Optum's minimum for a daily session note is place of service, start and stop time, who rendered the service, the specific service, who attended and the interventions that occurred (Optum ABA CPT FAQ, Q9). A note missing a stop time falls short of that minimum, so catch it in the weekly check, not at audit.

If keeping this ledger current across a full caseload is more than your team can carry, our ABA billing services track 15-minute unit usage against active authorizations.

Continuation requests have a window. Ask too early and the request may not be accepted. Ask too late and you risk a gap or a retrospective review.

We found no single industry deadline. Each payer publishes its own clock. Here are five examples:

Two things follow from this. First, an early request isn't automatically safe. Under Optum's rule a request sent 45 days ahead is outside the window. Second, late can cost more than a few days. Evernorth's guide links late requests to retrospective review, which can hold up the determination.

Put each authorization's end date and its request window in the calendar the day the approval is logged. If a reassessment is due, as with Aetna's 6-to-12-month cycle, schedule it so the scores are ready when the request goes in.

If request deadlines are slipping across payers, our behavioral health prior authorization services handle reauthorization tracking and submissions.

Ask for more before the units are gone. Add a code to the authorization before you bill it.

Clinical needs change mid-authorization. Behavior escalates, a parent-training goal gets added or a new technician joins the case. The approval doesn't change by itself. Here are two examples of what payers say about mid-period changes:

• Optum: for more services in the current approval period, call the ABA/Autism team and give the clinical rationale (Optum Q30). Include assessment hours in your treatment request when you call in (Optum Q12). Inside a cluster you can shift codes as clinically appropriate (Optum Q13).
• Virginia Medicaid: when the per-code rule started, existing fee-for-service authorizations continued to their end date. Additional units before the end of a current authorization go through Acentra Health's Atrezzo portal (Virginia DMAS bulletin). Cardinal Care members go through their MCO.

Now say you add 97156 parent training halfway through. Check whether the approval already covers it. Under a cluster structure it may sit in a cluster you already have. Under a per-code structure it may need a new or amended request. Either way, confirm before the first session is billed, not after the remit.

The ledger helps here too. If pace says a client will run out three weeks early, that's your cue to send the clinical rationale now while there's still time for a decision.

On Jan 1, 2027 the codes 97151–97158 are revised, six new codes are added and 0362T and 0373T are deleted. Authorizations that run across that date need checking.

At its September 2025 meeting the AMA CPT Editorial Panel accepted six new adaptive behavior codes. It also revised 97151–97158 and the guidelines, and deleted 0362T and 0373T, effective January 2027 (AMA Summary of Panel Actions, Sept 2025). In February 2026 the Panel also accepted guideline revisions for January 2027 (AMA Summary of Panel Actions, Feb 2026). The AMA says the CPT 2027 code set goes into effect on January 1 (AMA CPT 2027 release).

CMS's CY 2027 proposed rule describes the new set (CMS CY 2027 PFS proposed rule, §(47)):

• 97155 is redefined around the QHP directing the technician and analysis.
• A new QHP code covers direct treatment with analysis for one patient.
• A new QHP code covers non-face-to-face work such as reviewing data and session notes and modifying protocols.
• Harmful-behavior assessment and treatment get new codes delivered by two technicians, each with an add-on code for additional technicians. 0362T and 0373T are deleted.
• CMS proposes contractor pricing for the six new codes and no status change for the eight revised codes, which are already contractor priced.

That's a proposed rule and a final rule will follow. Until AMA and CMS publish the final numbers for the six new codes, don't load placeholder codes into your system.

What to do now:

• List open authorizations whose end date falls after Dec 31, 2026.
• Flag any that include 0362T or 0373T, or that rely on 97155 for QHP direct treatment.
• Ask each payer in writing how open approvals will carry over to the new codes.

Don't assume a crosswalk. Evernorth's policy notes that "deleted codes and codes which are not effective at the time the service is rendered may not be eligible for reimbursement" (Evernorth EN0499, Coding Information). Get the payer's answer before the first January session.

• Each new approval logged in the payer's structure (per code, cluster or monthly)
• Start and end dates in the calendar with the payer's request window
• Next week's scheduled units checked against remaining units
• Delivered units reconciled to billed units
• Concurrent units logged for both providers
• Daily units checked against MUEs and payer daily limits
• Session notes complete with start and stop times
• Continuation requests dated inside each payer's window
• New codes added to the approval before they're billed
• 2027 carry-over question sent for authorizations that span Jan 1

Not sure whether gaps like these are already costing you paid sessions? Start with a free revenue audit.

Payer and state rules vary and change. Confirm the details with each payer and your state Medicaid program. This isn't legal or coding advice.