Author: Lori Carlin, CPC, COC, CPCO, CCS, CRC


Author: Angela Wood, CPC
Senior Physician Auditor / Educator


(303) 801-0111

In part one we discussed procedure to procedure (“PTP”) edits. In this article we will discuss Medically Unlikely Edits (“MUEs”).


The Centers for Medicare and Medicaid Services (“CMS”) defines an MUE as “the maximum units of service reported for a HCPCS/CPT code on the vast majority of appropriately reported claims by the same provider/supplier for the same beneficiary on the same date of service.”


There are two types of MUEs, Claim line MUEs and date of service MUEs. This may just sound like semantics, but it really matters.


A claim line MUE is adjudicated based on the units billed on the line item of the claim. The Medicare Administrative Contractor (“MAC”) is specifically looking to see how many units were billed for that CPT or HCPCS code on that particular line item. In contrast, date of service (“DOS”) MUEs are adjudicated based on how many units of a given CPT or HCPCS code are billed by the same provider to the same patient on the same day. This means they will look at data across all claims billed by that provider for that patient on that DOS. They will sum up the units for that specific CPT or HCPCS code and then compare it to the MUE.


CMS updates all NCCI edits (including MUEs) once a quarter. We have provided a link below so you can download the file from the CMS website. You can use this file to determine what type of MUE edit your code has and what the maximum units are.


You will want to become familiar with the MUE Adjudication Indicators (“MAIs”) to properly utilize the MUE files.


1This is a line item edit.If documentation supports the units you have billed, you can use modifiers like 59 or anatomical modifiers on separate lines of the claim to get your units paid.
2Absolute date of service edit.No real recourse. MACs are restricted from overriding these edits during processing, reopening or redetermination.
3Per day edit based clinical benchmarks.If your documentation supports the units billed, the MAC can bypass the MUE during processing, reopening or higher-level appeal.


Let’s walk through a few examples.


Code 44950 Appendectomy has an MAI of 2 and an MUE of 1. This indicates the MUE for 44950 is an absolute per day MUE. We can only bill 1 unit of 44950. The MAC will look across all claims for this patient by the provider on this DOS and if they see more than one unit of 44950 billed, they will deny any units over 1. You cannot appeal to the MAC to review this because CMS does not allow them to pay more than 1 unit period. The MUE for 44950 is based on anatomical consideration since there is only one appendix.


Now, let’s look at a code that has an MAI of 3. CPT code 71045 Radiologic examination, chest; single view has an MAI of 3 and an MUE of 4. This means only 4 units of 71045 can be billed per date of service, per provider for a patient. However, if the clinical documentation supported medical necessity for 5 units, you could appeal to your MAC to review the initial determination and override the edit.


The NCCI manual has a lot of great information on how to properly bill units which should encourage you to keep up with all the updates. It also details how to properly report bilateral procedures. Be on the lookout for our next article where we will discuss this in detail.


Keeping up with all the nuances of NCCI edits can be exhausting. PERCS is here to help you remain compliant. If you have any questions or need assistance, please contact Angie Wood, CPC, Sr. Physician Auditor and Educator at or Lori Carlin, CPC, COC, CPCO, CCS, CRC, Principal, at They will be readily available to answer your questions and provide expert advice, so you are well equipped to move forward!