Therapy codes are not payable without one of these modifiers to distinguish the discipline of the plan of care under which the service is delivered. 

Use these modifiers for all plan types to ensure the correct billing category is applied.

• GN: Indicates services delivered under an outpatient speech-language pathology plan of care
• GO: Indicates services delivered under an outpatient occupational therapy plan of care
• GP: Indicates services delivered under an outpatient physical therapy plan of care

See also: Physical therapy billing