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Medically Unlikely Edits: Avoid denials and appeals properly coding the first time
Last Modified: 12/1/2024
Location: FL, PR, USVI
Business: Part A, Part B
First Coast is receiving appeals for denials of services in which the provider did not bill the initial claim with the appropriate number of units based on Medically Unlikely Edit (MUE) values. Many of the appeals filed for MUE denials denied due to an MUE Adjudication Indicator (MAI) 2 edit. MAI 2 is an absolute date-of-service limit that can’t be overridden or bypassed with a modifier. Since MAI 2 is a date-of-service edit and is absolute (will never change), these denials cannot be appealed.
CMS developed MUEs to reduce the paid claims error rate for Part B claims. An MUE for a HCPCS or CPT code is the maximum units of service that a provider would report under most circumstances for a single beneficiary on a single date of service. CMS publishes most MUE values on its website; however, some MUE values are confidential.
1. Practitioner services
2. Durable medical equipment
3. Facility outpatient hospital services
Part B MUEs are located in the practitioner file. The table contains four columns:
1. HCPCS/CPT Code: Contains code with MUE value.
2. Practitioner services MUE values: Maximum units of service a practitioner would report under most circumstances for a beneficiary on a single date of service.
3. MAI: Describes the type of MUE (claim line or date of service), or logic behind the edit.
• MAI 1: Applied at line level (claim line) – Appropriate use of modifiers to report the same code on separate lines of a claim will enable the reporting of medically necessary units of service in excess of MUE
• Modifier examples: 76, 77, 91, RT, LT, F1, F2
• MAI 2: Absolute criteria (date of service) – CMS has not identified any instances in which a higher value is payable. Since MAI 2 is a date-of-service edit and is absolute, these denials cannot be appealed. Justification would be impossible as shown in the example below:
• For example, an appendectomy has an MUE of 1 and MAI of 2. The maximum unit billable for an appendectomy is one because a patient only has one appendix.
While this example shows how MAI 2 prohibits billing the medically impossible, MAI 2 might also help avoid an error that is systematically impossible (e.g., CPT code 17000 used for lesion destruction states in the definition "first lesion"). By definition, it would be impossible to bill anything other than one unit of service. Additional units of service for lesion destruction would be billed with the add-on code +17
003 or code 17004.
• MAI 3: Value unlikely to appear on correctly coded claim but could, in unusual circumstances, be payable (date of service) – exceptions rare; supporting documentation required.
4. MUE Rationale: Provides underlying basis
If the number of units is over the MUE value, all units are denied. These denials may be appealed with supporting documentation. Note: Keep in mind that you cannot appeal denials with an MAI 2.
Many MUE denials are a result of incorrect billing. If you encounter a code with frequent denials due to an MUE, ensure the following:
• Submit records with the claim to support the medical necessity of the number of services reported
• The denial is NOT MAI 2. These denials cannot be appealed.
• The HCPCS/CPT code reported is correct
• The units of service were counted correctly
• An applicable and appropriately documented modifier was submitted, and
• The numbers of services reported were medically reasonable and necessary.
Note: The Washington Publishing Company maintains the CARCs and RARCs. Visit the
Washington Publishing Company 
website to view or print these codes.
Inquiries about the MUE program other than those related to MUE values for specific HCPCS/CPT codes should be emailed to
NCCIPTPMUE@cms.hhs.gov.
First Coast Service Options (First Coast) strives to ensure that the information available on our provider website is accurate, detailed, and current. Therefore, this is a dynamic site and its content changes daily. It is best to access the site to ensure you have the most current information rather than printing articles or forms that may become obsolete without notice.
