In simple words: This code is used when you get physical therapy services as part of a treatment plan, and you're not staying in the hospital overnight.

This modifier is appended to a Healthcare Common Procedure Coding System (HCPCS) code when the provider renders services that are part of a physical therapy plan of care for an outpatient. The medical documentation must include a diagnosis code that is consistent with a condition that requires physical therapy.

Example 1: A patient with a diagnosis of osteoarthritis of the knee receives outpatient physical therapy services including therapeutic exercises and manual therapy. The physical therapist appends modifier GP to the codes for these services., A patient with a diagnosis of low back pain receives outpatient physical therapy which includes ultrasound and electrical stimulation. Modifier GP is appended to the codes billed by the physical therapist., Following a rotator cuff repair, the patient receives physical therapy services in an outpatient setting. The therapist includes the GP modifier for appropriate codes billed.

Documentation must support the medical necessity of the therapy services, including the diagnosis, the plan of care, and the services provided. It should also clearly indicate that the service was provided in an outpatient setting.