Modifier XU: Unusual Non-Overlapping Service
Modifier XU unbundles a service that doesn't overlap the main procedure's usual parts. CMS's definition, when XU fits better than 59, and the NCCI denial traps.
Modifier XU is a HCPCS Level II modifier that tells Medicare a service bundled by a National Correct Coding Initiative (NCCI) edit was distinct because it didn't overlap the usual components of the main service. CMS defines it as "Unusual non-overlapping service, the use of a service that is distinct because it does not overlap usual components of the main service" (MLN1783722, April 2026). It is the most specific replacement for modifier 59 when the separation isn't a different site, encounter or practitioner.
Key takeaways
- XU is one of four X modifiers CMS created to replace 59 where possible: XE (separate encounter), XS (separate structure), XP (separate practitioner) and XU (non-overlapping service).
- CMS names two situations for XU: a diagnostic procedure that decided the treatment, and a diagnostic procedure after treatment that isn't an expected follow-up.
- XU only works on NCCI pairs with a modifier indicator of 1.
- Different code descriptions or different diagnoses never justify XU.
- XU doesn't change the rate; it lets the bundled code be paid.
Modifier XU · payment effect
With and without the modifier
75710 without XU · national office
$149.30
Extremity angiography
75710-XU · No change to the rate
$149.30
Unusual non-overlapping service. Unbundles an NCCI pair; each service is paid at its own rate.
When to use modifier XU
NCCI procedure-to-procedure (PTP) edits pair a column 1 code (paid) with a column 2 code (denied). When the pair's modifier indicator is 1, an NCCI-associated modifier can bypass the edit if the services really were separate. CMS lists two situations where 59 or XU applies because the services were separated in time and didn't overlap, even in the same encounter (MLN1783722):
- A diagnostic procedure before a therapeutic one, when it is the basis for the treatment. It counts as separate only if it happened first and wasn't mingled with the treatment, clearly gave the information needed to decide whether to proceed, and isn't something the treatment would have required anyway. Example: a diagnostic angiogram (75710) that shows a blockage and leads the physician to treat it in the same session.
- A diagnostic procedure after a completed therapeutic one, when it isn't a common, expected or necessary follow-up. It must come after the treatment ends, not be mixed with it, and not be a service the treatment includes.
CMS allows XU on either the column 1 or column 2 code (Change Request 11168). Documentation isn't sent with the claim, but the record must show the timing and the decision.
When not to use modifier XU
- Different anatomic site in the same session. Use XS, or RT/LT and other anatomic modifiers.
- Separate encounter on the same day. Use XE. Two timed services in separate blocks are 59 or XE, not XU.
- Different practitioner. Use XP.
- A separate E/M visit. Use modifier 25; X modifiers never go on E/M codes.
- The NCCI indicator is 0. No modifier can bypass it.
- The payer doesn't accept X modifiers. Some commercial payers only recognize 59.
How modifier XU affects payment
XU has no payment percentage. When it is valid, the column 2 code is paid at its normal fee schedule amount instead of being denied. Multiple procedure reductions (modifier 51) and medically unlikely edits still apply. Because XU replaces a denial with a payment, it is one of the modifiers MACs and auditors review most closely.
XU vs 59, XE, XS and XP
| Modifier | Distinct because | Typical use |
|---|---|---|
| XU | The service doesn't overlap the main service's usual parts | Diagnostic study that decided the treatment |
| XS | Separate organ or structure | Lesions in different anatomic regions |
| XE | Separate encounter on the same date | Patient returns later in the day |
| XP | Different practitioner | Another provider performs the second service |
| 59 | Any of the above when no X modifier fits | Payers that don't accept X modifiers |
CMS's instruction is to use the X modifiers instead of 59 whenever possible and to use 59 only when no more specific modifier is appropriate. Never report XU and 59 on the same line for the same reason. The modifier 25 vs 59 guide covers the visit-plus-procedure version of this decision.
FAQ
Are modifier 59 and XU the same?
No. Both bypass NCCI edits, but XU says specifically that the service didn't overlap the main service. 59 is the general modifier for any kind of separation. CMS prefers XU over 59 when it fits.
Can XU and 59 be billed together?
Not for the same reason on the same line. They describe the same thing at different levels of detail, and CMS's instruction is to use the more specific X modifier instead of 59.
What is the XU modifier for?
For a service that NCCI bundles with another, when the record shows it didn't overlap the main service, most often a diagnostic procedure that led to the treatment, or one after treatment that wasn't an expected follow-up.
What are modifiers XE, XP, XS and XU?
They are CMS's specific subsets of modifier 59: XE for a separate encounter, XP for a separate practitioner, XS for a separate structure and XU for an unusual non-overlapping service.
Do I need a different diagnosis to use XU?
No, and a different diagnosis alone isn't enough. The codes stay bundled unless the services were at different sites, separate encounters, or one of CMS's non-overlap exceptions.
Keep reading
- Modifier 59, the general distinct-service modifier.
- Modifier 25 vs 59 for visits on procedure days.
- Modifier 51 for multiple-procedure reductions that still apply.
- Codes on this page: 75710 97140 93015
Sources: CMS MLN1783722, Proper Use of Modifiers 59, XE, XP, XS & XU (April 2026); CMS Change Request 11168; Medicare NCCI Policy Manual, ch. 1 (2026). Verified October 6, 2026.
