Medically Unlikely Edits (MUE) Program

Published 10/02/2023

The Centers for Medicare & Medicaid Services (CMS) Medically Unlikely Edits (MUE) program was developed to reduce the paid claims error rate for Medicare claims. MUEs are designed to reduce errors due to clerical entries and incorrect coding based on anatomic considerations, HCPCS/CPT® code descriptors, CPT® coding instructions, established CMS policies, nature of a service/procedure and unlikely clinical treatment.

Medicare adjudicates MUEs against each line of a claim rather than the entire claim. If a HCPCS/CPT® code is reported on more than one line of a claim by using CPT® modifiers, each line with that code is separately adjudicated against the MUE. The entire claim line is denied if the units of service on the claim line exceed the MUE value. Since claim lines are denied, the denial may be appealed for HCPCS code with a MUE adjudication indicator (MAI) of "1" or "3."

HCPCS codes with a MAI "2" are absolute date of service (DOS) and per day edits based on policy.  The MAI "2" designation indicates that units of service on the same DOS more than the MUE value would be considered impossible because it was contrary to statute, regulation or sub-regulatory guidance.

Denial may be appealed for HCPCS code with an MAI "2." However, please note that the CMS sub-regulatory guidance includes clear correct coding policy that is binding on both providers and the MACs. Providers may submit a corrected claim and request to reduce the number of units by submitting a redetermination request with a correct UB attached.

Since each claim line is adjudicated separately against the MUE of the code on that line; an appropriate use of CPT® modifiers to report the same code on separate lines of a claim will enable a provider to report medically reasonable and necessary units of service more than an MUE. Modifiers such as CPT® modifier 76 (repeat procedure by same physician), CPT® modifier 77 (repeat procedure by another physician), anatomic HCPCS modifiers (e.g., RT, LT, F1, F2), CPT® modifier 91 (repeat clinical diagnostic laboratory test), and CPT® modifier 59 (distinct procedural service) will accomplish this purpose. CPT® modifier -59 should be utilized only if no other modifier describes the service.

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