The X{EPSU} Modifiers Further Define Modifier 59

Same patient, same day, two separate nonevaluation and management services or procedures … this can present a coding challenge in light of the Medicare National Correct Coding Initiative (NCCI).

NCCI edits reject codes on claims that should not be reported together with certain other codes in all or most situations because, typically, the procedure identified by one code is bundled into the procedure identified by the other.

Sometimes, however, two procedures that normally would be bundled actually are distinct. The codes you need to override NCCI edits in these circumstances – when appropriate – are modifiers XE, XS, XP, XU, and 59.

Current Procedural Terminology modifier 59 is the overarching “distinct procedural service” modifier, but think of it a modifier of last resort – use it only when none of the more specific modifier applies. Turn first to Healthcare Common Procedure Coding System modifiers XE, XS, XP, XU to report a distinct procedural service with greater specificity. These codes were created to act as subsets of modifier 59.

Modifier XS
Use XS (“separate structure”) for procedural services that you (1) perform at different anatomic sites, (2) would not ordinarily perform or encounter on the same day, and (3) cannot describe by one of these more specific anatomic NCCI modifiers: RT, LT, E1-E4, FA, F1-F9, TA, T1-T9, LC, LD, RC, LM, or RI.

Under NCCI, “different anatomic sites” means different organs or anatomic regions or, in certain instances, different lesions in the same organ or anatomic regions. Treatment of contiguous structures in the same organ or anatomic region does not constitute treatment of different anatomic sites. Typically, NCCI edits prevent the billing of lesions and sites not considered separate and distinct. Thus you would use modifier XS to identify clearly independent services, for example, a biopsy on a facial lesion that was distinct from the excision of a separate benign lesion on the face.

Modifier XE

Use XE (“separate encounter”) for procedural services you perform in different sessions on the same day and cannot describe using one of these more specific NCCI modifiers:  24, 25, 27, 57, 58, 78, 79, or 91. For example, a cardiovascular stress test and a rhythm ECG performed in the same session would be bundled under NCCI edits. But if you perform the stress test in the morning and the ECG in the afternoon, even if on the same day, you can indicate they were separate services with modifier XE.

You also can use modifier XE for two services described by timed codes (e.g., per 15 minutes, per hour) you provide during the same encounter, but only when one service is completed before the subsequent service begins.

Modifier XP

Use XP (“separate practitioner”) when one physician in a practice performs a service and another physician in the same specialty from the same practice performs a normally bundled service on the same patient, for medically necessary reasons. An example might be in the care of a trauma patient. Typically, Medicare considers two physicians in the same group with the same specialty performing services on the same day as the same provider. Using modifier XP merely to parcel out services among physicians in a group is not a correct use of it.

 Modifier XU

Use XU (“unusual non-overlapping service”) to indicate a service that is distinct because it does not overlap usual components of the main service. An example is performing a cardiac diagnostic test, and as a result of that test, performing a cardiac procedure later in the same day. If the diagnostic procedure is an inherent component of the surgical procedure, however, it would not be reported separately. A diagnostic procedure you perform after a completed therapeutic procedure might qualify for modifier XU, but only when the diagnostic procedure is not a common, expected, or necessary follow-up to the therapeutic procedure.


  • Don’t apply any of these modifiers simply because the narrative description of the two codes of the code pairs are different.
  • Don’t report any of these modifiers with an evaluation and management code.
  • Do have sound documentation to support a different session, different procedure or surgery, different site or organ system, separate incision/excision, separate lesion, or separate injury (or area of injury in extensive injuries).

Find more information from the Centers for Medicare & Medicaid Services’ MLN Matters No.: SE1418 Revised and Novitas Solutions.

Have coding or billing questions? Contact TMA’s certified coders at (800) 880-1300, ext. 1414 or at paymentadvocacy[at]texmed[dot]org for help.

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Last Updated On

December 27, 2021

Originally Published On

June 10, 2014

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