Modifier XU: Unusual non-overlapping service
When it is appropriate
Use XU when the column two service represents work that does not overlap the usual components of the column one procedure, capturing an unusual, non-overlapping situation that the other X modifiers do not describe.
When it is not appropriate
Do not use XU for a service that is, in fact, an inherent part of the primary procedure's usual work; that is exactly the bundling NCCI intends to enforce.
CMS preference
Use XU over 59 as the more specific choice whenever the situation is genuinely about non-overlapping service components rather than encounter, structure, or practitioner differences.
Retrieved 2026-07-18.
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