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Modifiers GP, GO, GN: Mandatory Therapy Disciplines

Last Updated: October 27, 2025

Medicare requires every single outpatient therapy claim to identify the discipline (specialty) under which the service was provided. Failing to append the correct discipline modifier results in an immediate, automated rejection.

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The Three Therapy Modifiers

  • Modifier GP: Services delivered under an outpatient Physical Therapy plan of care.
  • Modifier GO: Services delivered under an outpatient Occupational Therapy plan of care.
  • Modifier GN: Services delivered under an outpatient Speech-Language Pathology plan of care.

Who Needs to Use Them?

These are not just for private PT clinics. If a primary care physician (MD/DO) or orthopedic surgeon performs and bills for a therapeutic exercise (97110) in their office, they MUST append Modifier GP to the code.

NCCI and Modifier Stacking

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Not sure if these codes bundle? Check the latest Medicare NCCI database updates before you bill.

These modifiers are informational and must be stacked with pricing/unbundling modifiers. (e.g., 97140-59-GP). Put the pricing/unbundling modifier first, followed by the discipline modifier.

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