On AAPC FAQ page:

“How do I cancel an exam?
This service is available on our website for your convenience, located under your upcoming events, on the main page. Click on “Cancel This Exam” link. An AAPC Exam Service Charge will be assessed ($100.00 US and $150.00 for all international exams). Exam must be cancelled 21 days prior to scheduled exam date. The Exam Service Charge must be paid in full prior to rescheduling your exam.”