MUEs are used by Medicare to help reduce improper payments for Part B claims. This article will address the use of the National Correct Coding Initiative (NCCI) and Medically Unlikely Edits (MUEs) and how they are used by CMS.  MUEs are applied to Healthcare Common Procedure Coding System (HCPCS) and Current Procedural Terminology (CPT) codes to indicate the maximum number of units commonly used on a single date of service.    

CMS assigns Medically Unlikely Edits (MUEs) for HCPCS/CPT to most codes. However, not every code has an MUE assigned.  According to CMS, MUE edits are used to limit tests and treatments provided to a Medicare patient for a single date of service or for a single line item on a claim form. It is important to understand that MUEs are not to be used as utilization guidelines; CMS is concerned that providers will incorrectly interpret MUE values as utilization guidelines. MUE values do NOT represent units of service that may be reported without concern about medical review. Providers should continue only to report services that are medically reasonable and necessary. 

According to CMS, although CMS publishes most MUE values on its website, other MUE values are confidential.  Confidential MUE values are not releasable. 

Find-A-Code lists the MUE values that have been released by CMS; these MUEs can be found on the CPT code information page under the additional information for easy access. 

Reminder: MUEs are used on a case-by-case basis and are not to be used as utilization guidelines. In other words, if your clinical data reflects the need for additional units and it is medically reasonable and necessary, it should be reported.

Reasons for MUE Rationale 

  • Published Contractor Policy
  • CMS Policy
  • Clinical: Data
  • Nature of Equipment 

Bilateral Procedures and MUEs

You may be wondering how MUEs work with bi-lateral procedures, good question. We first need to understand Medicare's correct coding instructions; we are required to report a bilateral procedure with a 50 Modifier and one Unit of Service (UOS) on the same line. To understand if a procedure can be performed bilaterally, pay careful attention to the following. 

The code description: Always start here; the code may state in the description if the procedure is bilateral, for example, 27395- Lengthening of hamstring tendon: multiple tendons, bilateral.

Bilateral Indicator: Medicare uses what is called Medicare Physician Fee Schedule (MPFS) indicators; one indicator is called a Bilateral Surgery Indicator, letting us know whether special payment rules apply, such as the 150% payment rule for a bilateral procedure. The bilateral surgery indicator lets us know if modifier 50 is allowed to be reported with the procedure/CPT code. Let's take a look at the same CPT code, 27395- Lengthening of hamstring tendon: multiple tendons, bilateral.  CMS has assigned a bilateral Surgery indicator of "2," indicating the 150% payment adjustment for bilateral surgery does NOT apply. Therefore, you cannot code this procedure with Modifier 50, as the code already includes a bilateral procedure in the description.  


What are the MAI indicators?

Each MUE is assigned a Medicare Adjudication Indicator (MAI), further specifying how MACS look at MUEs. MUEs and MAIs are used by providers, suppliers, and MACS in all settings.  These are the most common and published MAIs. There are MUEs with a value of less than 1 and a value of 4 or more that are not published due to concerns from CMS about fraud and abuse.

MAI 1 -  adjudicated as a claim line edit 
MAI 2 -  per day edits based on policy (Impossible to bill excess MUEs)
MAI 3 -  per day edits based on clinical benchmarks (UOS in excess of the MUE value were actually provided, were correctly coded, and were medically necessary)

MUEs are automatically denied or deemed an "auto-deny edit."

Because they are auto-deny edits, it is important to be aware of the MAIs assigned to each MUE. These types of denials should all be appealed and sent back for reconsideration if denied incorrectly.  ASC Providers (specialty Code 49) cannot use modifier 50 (Bilateral procedure); therefore, the MUE with an MAI of 1 is automatically doubled by the MAC.

Incorrect usage of MUEs will be denied as a coding denial, not a clinical or medically necessary denial. 

Claim Remark Codes 

On your EOB or remittance advice, to identify claims that fail the MUE edit claim, remark codes N362 and MA01 will be used.   

Durable Medical MUEs
CMS also assigns MUEs to Durable medical using HCPCS codes as mentioned above.  


For questions on a specific claim, you will need to contact your MAC representitave. If your questions are about the MUE program or questions related to NCCI (PTP, MUE, and Add-On) edits, send them to

Appeals and Reconsideration

According to HHS If a national healthcare organization, provider, or other party wants to submit a request for reconsideration of an MUE value, the procedure described in the Frequently Asked Questions (FAQs) should be followed.  See the web link below.  Such requests should be addressed to:

National Correct Coding Initiative