Modifier AS

Physician Assistant (PA), Nurse Practitioner (NP) or Clinical Nurse Specialist (CNS) assistant at surgery services.


Append this modifier to appropriate procedure codes when Non-Physician Practitioners (NPPs) are assisting a principal surgeon as an assistant surgeon. The assistant at surgery provides more than ancillary services. NPPs include a CNS, NP and PA.

Correct Use

  • The Medicare Physician Fee Schedule (MPFS) Indicator/Descriptor lists under column A will confirm if assistant at surgery is allowed.
    • 2 = payment restriction for assistants at surgery does not apply to this procedure. Assistant surgeon may be paid).
  • NPP, mid-level practitioner or advance practice practitioner (APP)
    • Append this modifier only
  • NPP must accept assignment
  • NPPs are allowed 85% of 16% physician fee allowable or 14% of surgery

Incorrect Use

  • Inappropriate for NPPs to use modifiers 80, 81 or 82 (physician only modifiers)
  • Modifier 80 (assistant surgeon), 81 (minimum assistant surgeon) or 82 (qualified resident surgeon not available) with physician (MD/DO) assisting at surgery



Last Updated Oct 25 , 2022