An ABN is Advanced Beneficiary Notice-a written document that health care providers give to patients under certain circumstances, who are Medicare beneficiaries. According to CMS guidelines, the ABN must be given to patients when health care provider believes Medicare probably will not or certainly will not pay for the items or services that the patient has requested. The ABN must include an explanation that the patient can understand as to why the health care provider believes so. Vicki Sue Miller (coder)