RAC Audit

“I have had a RAC audit for a L1951 (from performant) claiming an overpayment stating, “the custom- fitted orthosis did not include a detailed description of the necessary modifications.” L1951 is a prefab which does not require modifications. Where can I go to get any documents (Medicare preferred) stating that L1951 is prefab and as such does not require modifications to respond to this demand?”

Can you please explain what a “RAC” audit is?