Glossary · Updated Aug 10, 2026
MUE (Medically Unlikely Edit)
A Medically Unlikely Edit (MUE) is the maximum number of units of a HCPCS/CPT code that CMS considers plausible for one patient on one date of service. It is a claims-editing threshold meant to catch clear billing errors—not a statement of the correct or typical number of units.
What the value catches Copy link
An MUE value guards against gross errors like a misplaced decimal, a per-unit code billed as a per-encounter count, or a data-entry mistake—not against clinically implausible-but-real high-unit claims, which is why exceeding the value does not automatically mean the billing was wrong.
The adjudication indicator Copy link
How an excess is handled depends on the MUE adjudication indicator (MAI). An MAI of 1 is a claim-line edit: each line is checked on its own, and reporting the code on separate lines with appropriate modifiers allows medically necessary units above the limit, though contractors restrict those modifiers for some codes. An MAI of 2 or 3 is a date-of-service edit: units are summed across all lines for that code on that date before the limit is checked. The difference between them is what a contractor may do about an excess—an MAI of 2 is absolute, and CMS instructs contractors that overriding it would be contrary to CMS policy, while an MAI of 3 rests on clinical benchmarks and may be bypassed where the contractor has evidence the units were provided, correctly coded, and medically necessary. Any MUE denial may be appealed, whatever the indicator; the indicator governs the bypass, not the right to appeal.
| MAI | Edit type | How excess units are handled |
|---|---|---|
| 1 | Claim-line edit | Each line checked separately; appropriate modifiers on separate lines allow medically necessary units above the limit |
| 2 | Date-of-service edit, absolute | Units summed across all lines for that code on that date; CMS instructs contractors that an override would be contrary to CMS policy |
| 3 | Date-of-service edit, clinical benchmarks | Units summed the same way, but a contractor may bypass the edit on evidence the units were provided, correctly coded, and medically necessary |
A ceiling, not a target Copy link
A code without a published MUE simply has no unit limit from this particular edit—it is not evidence that unlimited units are appropriate. Likewise, billing right up to the MUE limit is not itself a signal of correct coding; the limit only screens out clearly implausible unit counts.
Frequently asked Copy link
Does exceeding the MUE always deny the claim?
Exceeding a claim-line MUE denies all units on that line; exceeding a date-of-service MUE denies all units for the code on the current claim. What you can do next depends on the adjudication indicator. On a claim-line edit (1), reporting the code across separate lines with appropriate modifiers can carry medically necessary units above the limit. An absolute date-of-service edit (2) is one CMS instructs contractors not to override. A clinical date-of-service edit (3) may be bypassed where the contractor has evidence the units were provided, correctly coded, and medically necessary.
Can an MUE denial be appealed?
Yes. CMS states that denials due to claim-line or date-of-service MUEs may be appealed to the local claims processing contractor, whatever the adjudication indicator. The indicator decides whether a contractor may bypass the edit, not whether you may appeal the denial.
Is there an MUE for every code?
No. Codes without a published MUE are not limited by this edit, though other edits (like PTP) may still apply.
Sources Copy link
Written from primary CMS sources—see how we source, compute, and verify everything on this site.
- An MAI of 1 marks a claim-line MUE, while an MAI of 2 or 3 marks a date-of-service MUE. —CMS Medicare NCCI Policy Manual (2026)
- On a claim-line MUE, appropriate use of CPT modifiers to report the same code on separate lines lets each line be adjudicated separately against the limit, though contractors have rules restricting those modifiers for some codes. —CMS Medicare NCCI Policy Manual (2026)
- An MAI of 2 is an absolute date-of-service edit, and CMS instructs claims processing contractors that overriding it during processing, reopening, or redetermination would be contrary to CMS policy. —CMS Medicare NCCI Policy Manual (2026)
- An MAI of 3 rests on clinical benchmarks, and a contractor with evidence that excess units were actually provided, correctly coded, and medically necessary may bypass the edit. —CMS Medicare NCCI Policy Manual (2026)
- Denials due to claim-line MUEs or date-of-service MUEs may be appealed to the local claims processing contractor. —CMS Medicare NCCI Policy Manual (2026)
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