If I am doing an audit such as that, I like to first find out the exact responsibilities of the biller as well as their credentials. For example you say you are looking to make sure they are using correct codes, for me I would first find out if coding were a responsibility of the biller and if so are they properly trained/certified. This makes a difference even before beginning the audit. Then I have the following reports run by carrier: payments, adjustments, denials/rejections, and aging report. Then I gather the report for all CPT codes billed (by carrier) as well. If you are doing an audit to determine proper coding, you will most likely need all patient charts for the audit and I'm assuming you are a correctly trained and/or certified coder. Also I would caution you on the removal of patient charts from the provider's office. I never conduct any audit with records removed from the office due to liability issues. These type of audit's I do IN their office and is billed hourly in addition to any travel/accommodations that might be needed. I also have a separate contract and it specifically states there will be limited to no contact with the current biller in regards to the audit (that can bias the audit) Hope this helps.