CPT code 99396 refers to a preventive medicine evaluation for patients aged 65 and older, involving a comprehensive annual wellness visit that includes medical history, physical examination, counseling, screenings, and risk assessment. Proper billing for this code requires adherence to specific guidelines such as medical necessity, time documentation, and accurate coding. Primary care providers can optimize reimbursement by following best practices in documentation and coding, and can seek assistance from medical billing specialists like Legion Healthcare Solutions.