What ABA Providers Should Know About CMS, NCCI, and MUEs

Billing for ABA therapy isn’t just about entering CPT codes and hoping for a clean claim. Behind every approved claim are federal rules, coding standards, and volume limits that shape how payers evaluate ABA services. Three of the most important players in this system are CMS, NCCI, and MUEs.

Most ABA providers learn about these rules the hard way through denials. But understanding CMS guidelines, NCCI edits, and MUEs before you bill can save you from denials, payment delays, and compliance headaches.

Understanding the Basics: CMS, NCCI, and MUEs

What Is CMS?

CMS stands for the Centers for Medicare & Medicaid Services, the agency that sets national coverage and billing standards.

CMS creates the billing rules that most of the healthcare industry follows. Commercial insurance companies, managed care organizations, and state Medicaid programs often adopt CMS guidelines as their standard.

In short, even when you bill a private payer, you’re often still playing by CMS rules.

How CMS Affects ABA Providers

Even when every client has commercial insurance, CMS rules still influence your billing.

Why this matters to ABA providers

• CMS establishes coverage standards that shape how states reimburse adaptive behavior services.

• Many commercial insurers follow CMS code definitions, time requirements, and documentation expectations.

• CMS updates influence reimbursement trends, audits, and compliance benchmarks.

Even if 100% of your clients have commercial insurance, you're still subject to CMS-based billing rules because those commercial payers adopted them.

What Is NCCI?

The National Correct Coding Initiative (NCCI) prevents improper payments by identifying incorrect code combinations, known as edit pairs. These rules determine whether certain CPT codes can be billed together.

In ABA billing, NCCI helps you

• Avoid coding combinations that trigger automatic payer denials.

• Ensure your reported services follow medical necessity and standardized coding logic.

• Protect your practice from preventable rejections that slow cash flow.

Example

If you submit two codes that NCCI classifies as mutually exclusive, the payer will deny one or both lines, even if the service was legitimate.

What Are MUEs (Medically Unlikely Edits)?

MUEs are limits created under the National Correct Coding Initiative (NCCI) to set the maximum number of units a provider can bill for a specific CPT code on a single date of service. The idea is simple: these limits act as a safeguard against billing errors or unrealistic unit reporting.

When a claim goes over the MUE value, a payer may do one of two things:

• Pay only up to the allowed unit limit, or

• Deny the entire claim line outright.

It’s also important to remember that not every CPT code has an MUE, and not every payer treats them the same way. Some Medicaid programs follow CMS limits closely. Others don’t. Commercial payers may use CMS values, modify them, or set their own.

Real scenario

Your RBT provides 6 hours of ABA therapy (24 units of 97153). You accidentally enter 64 units instead of 24. The claim is denied for exceeding the MUE. Even though the error is obvious, you still have to correct and resubmit.

Current MUE Limits for ABA CPT Codes

These values originate from the ABA Coding Coalition and CMS updates. Most payers still follow them:

CPT Code	MUE Limit (Units per Day)	Notes
97151	8 for Medicare; ~32 for Medicaid	Medicare level is still widely followed by commercial payers
97152	16	Increased from 8
97153	32	Common ABA treatment code
97154	18	Increased from 12
97155	24	The request for 32 units was denied
97156	16	Parent training
97157	16	Group adaptive behavior
97158	16	Group treatment
0362T	16	Increased from 8
0373T	24	Severe behavior code

If you exceed these limits, the MAI (MUE adjudication indicator) determines whether you can appeal the denial. Most ABA codes fall under MAI 3, meaning appeals are possible—but the documentation burden is high.

How These Rules Influence ABA Billing

CMS Shapes Coverage and Coding Logic

Even if your caseload is mostly commercial insurance, the underlying rules often originate from CMS. Commercial payers lean heavily on CMS for defining how ABA codes should be used, what documentation is expected, and which provider types can bill each code.

CMS guidance affects areas such as:

• When supervision and treatment codes can be billed together

• Expected assessment durations and repeat frequency

• Requirements for one-to-one versus group services

• Credentialing and provider qualifications for each CPT code

A simple example

Medicaid raised the MUE for 97151 to 32 units (eight hours), but Medicare kept it at 8 units (two hours). Some payers adopted the Medicaid value. Others stayed aligned with Medicare. Practices billing multi-hour assessments suddenly saw denials, not because the service was unnecessary, but because the payer followed the stricter MUE.

Are NCCI Edits Triggering Your ABA Claim Denials?

ABA teams often assume denials come from missing authorizations or diagnosis issues. But a large share of preventable denials is actually tied to NCCI edits.

Common NCCI-related denial triggers include:

Invalid Code Combinations: Certain codes cannot be billed together without proper justification.

Missing or Incorrect Modifiers: Modifiers like 59, XE, or XU are often required to show that two services were distinct.

Overlapping Time Documentation: If one staff member appears to deliver two services at the same time, the claim flags as an error.

Incompatible Code Usage: For example, billing a full assessment and a full treatment session during overlapping time periods.

Quick way to identify issues

Review your top 20 denial codes each month and look for phrases such as:

• NCCI edit

• bundled service

• code pair

• unbundling

This simple check often points directly to the problem area.

Why MUE Limits Can Reduce Your Reimbursement Without Warning

MUEs aren’t just technical billing rules sitting in a CMS table. They quietly decide how many units a payer will actually reimburse no matter how much care you delivered, and even when you have a perfectly valid authorization in your hand. That’s the part that catches most teams off guard.

Example

A plan may approve ten hours of 97153, but if they enforce a six-hour MUE, you’ll only be paid for six hours unless you appeal and justify the additional time.

FAQ

1. What is the difference between NCCI and MUE edits?

NCCI edits decide which codes can be billed together, while MUE edits limit how many units of a code a payer will reimburse in one day. NCCI prevents incorrect combinations; MUE prevents unrealistic quantities.

2. Are ABA services covered by Medicare?

Medicare does not broadly cover ABA therapy. Coverage exists mainly through specific demonstrations or limited programs. Most ABA services are funded through Medicaid or commercial insurance, which follow their own rules based on CMS guidance.

3. What is the MUE for 97153?

The current MUE for CPT 97153 is 32 units per date of service. Some payers may enforce stricter limits, so checking each payer’s policy is important to avoid unexpected reductions or denials.

Conclusion

In ABA billing, understanding CMS, NCCI, and MUEs isn’t just a compliance exercise it’s a practical necessity for every ABA provider trying to stay ahead of denials and maintain predictable cash flow. 

The more familiar your team becomes with these guidelines, the fewer surprises you’ll face in AR, appeals, and payment timelines. Understanding CMS, NCCI, and MUEs isn’t just about revenue it’s about making sure your clients receive uninterrupted services supported by clean, compliant billing.