Question: Our emergency department physician is performing multiple procedures during a trauma encounter. One of these procedures needs to be billed using an unlisted CPT® code. However, the existing CPT® code we are comparing it to would need a modifier 59 appended when billed along with the other procedures the physician performed. Should I append a modifier 59 to the unlisted procedure code? Texas Subscriber Answer: If a procedure you’re coding requires that it be submitted with an unlisted CPT® code, you should never append a modifier to the unlisted code. This rule exists across the board for all modifiers, including laterality modifiers such as LT (Left side), RT (Right side), and 50 (Bilateral procedure), and overriding modifiers such as 59 (Distinct procedural service). You’ll see that CPT® Assistant (August 2018; Volume 28, Issue 8) broaches this subject in response to a reader question inquiring about the use of modifier 62 (Two surgeons) on an unlisted procedure: “Although modifier 62, Two Surgeons, is typically appended to procedure codes when performed by co-surgeons, it is not appropriate to append modifiers to unlisted procedure codes because these codes do not describe specific procedures. Instead, when reporting an unlisted code to describe a procedure or service, it is necessary to submit supporting documentation (for instance, a procedure report) along with the claim to provide an adequate description of the nature, extent, and need for the procedure, as well as the time, effort, and equipment necessary to provide the service.” Therefore, you should avoid using modifiers with your unlisted codes, and instead should include your supporting documentation to reflect exactly what was performed.