Occupational Therapy Assistants/Physical Therapy Assistants Modifier Policy​ Despite challenges from National Therapy Associations and other national therapy stakeholders, CMS has proposed Occupational Therapy Assistants and Physical Therapy Assistants payment reduction modifier policy that would reimburse only 85% of the Medicare fee schedule for services that involve both a therapist and assistant if the assistant provides therapy care for more than 10% of the total treatme