Modifier GP

Medicare uses three discipline modifiers to tie each therapy line to the plan of care behind it: GP for physical therapy, GO for occupational therapy and GN for speech-language pathology. The rule reaches everyone who bills a listed therapy code, from therapists in private practice to physicians, nonphysician practitioners, hospitals, skilled nursing facilities and outpatient rehabilitation providers. The modifiers identify therapy whether or not a financial limitation is in force, and Medicare’s claims records use them to track each patient’s therapy spending. They do not let anyone bill a service they are not qualified to furnish.

The edits are mechanical, so claims fail on them mechanically. A professional claim with an always-therapy code and no therapy modifier is returned, and Medicare’s instructions pair that denial with CARC 4¹. Listed codes billed by a physical therapist in private practice always count as therapy. Sometimes-therapy codes billed by a physician or nonphysician practitioner may go out without a modifier when the service was not therapy. On institutional claims, a physical therapy revenue code line may carry only GP, and no line may carry more than one discipline modifier.

Two more modifiers travel with GP. CQ flags a service that a physical therapist assistant performed all or some of, and it must be paired with GP, or the claim is returned as unprocessable; since January 1, 2022 those lines have been paid at 85 percent of the Part B payment that would otherwise apply¹. KX joins the line once the patient’s therapy spending passes the annual threshold and the record shows the care is still medically necessary.