When it comes to Medicare, a lot can change in four years—whether it be the rise and fall of functional limitation reporting or answers to questions like, “Do outpatient rehab therapists have to report MIPS?” (You can get that answer here, by the way.) So, when CMS introduced the X modifiers back in 2015 and told PTs, OTs, and SLPs they wouldn’t have to use them, anyone familiar with Medicare rules knew that advice was subject to change. And yet, here we are, nearly four years later, and the question of when therapists will have to use X modifiers remains largely up in the air. Still, therapists may have to use these modifiers eventually, so it’s important they know how to use them correctly. With that in mind, here’s everything we know so far about X modifiers as they relate to rehab therapy:

Setting the Stage for the New X Modifiers

A little background: In January 2015, CMS issued new guidance for proper use of modifier 59. As part of that announcement, the agency established four new modifiers—collectively referred to as -X{EPSU} modifiers—to better define distinct procedural services. These new codes include:

  1. XE (Separate Encounter): A service that’s distinct because it occurred during a separate encounter
  2. XS (Separate Structure): A service that’s distinct because it was performed on a separate organ/structure
  3. XP (Separate Practitioner): A service that’s distinct because it was performed by a different practitioner
  4. XU (Unusual Non-Overlapping Service): A service that’s distinct because it doesn’t overlap the usual components of the main service

Misuse of modifier 59 has gotten some providers into hot water. Per CMS, the modifier has been “associated with considerable abuse and high levels of manual audit activity.” Thus, the introduction of the new HCPCS modifiers made sense. In fact, the new subsets allow for greater coding specificity, which theoretically would reduce errors and misuse. But, what are the guidelines for using modifier 59, anyway? Glad you asked.

Understanding When to Use Modifier 59

As indicated above, modifier 59 should only be used to identify distinct procedures or services that aren’t typically billed together, but were appropriately provided and are separately billable given the circumstances. Moreover, clinicians, coders, and billers should only use it as a last resort—when there’s not a better option. Here’s when you should apply modifier 59:

  • When you’re billing for two services that form a National Correct Coding Initiative (NCCI) edit pair—also called linked services—and you provided those services separately and independently of one another;
  • When your documentation supports characterizing those services as separate and distinct; and
  • When no other, more descriptive modifier is available.

Now, you’re probably scratching your head on that last bullet. After all, the reason CMS created these new -X{EPSU} modifiers in the first place was to provide practitioners with a library of more descriptive modifiers. But, while other healthcare providers were given the green light to use those modifiers in 2015, physical therapists weren’t immediately required to use them. However, according to this 2018 APTA resource, “movement toward the use of these modifiers—and greater scrutiny of claims using the 59 modifier—is happening.” (CMS also released additional clarification on the use of X modifiers in early 2018.)

Determining Where We Go From Here

So, we know that generally speaking, PTs, OTs, and SLPs still don’t have to use the X modifiers, but should they? According to compliance expert Rick Gawenda, probably not. During a recent open forum-style webinar, Gawenda explained that while therapists can use these modifiers if they’d like, he still recommends using modifier 59, as some MACs may not have the new modifiers built into their automatic claims processes yet.

That means rehab therapists can continue to use modifier 59 when billing for two services that meet the criteria outlined in the previous section. But, like anything else in health care, changes could happen fast—which means rehab therapists should keep an eye out for any further instruction that might come down the pike from either CMS or commercial insurance payers. (On that note, if you haven’t already, be sure to subscribe to the WebPT Blog to stay ahead of any updates.)


Still need to brush up on modifier 59? Check out this blog post or our modifier webinar recording for more information.