In the formal course of merchant credit card and other electronic payment processing, a Checklister is a computer program that acts as a system – or what is known as a “gatekeeper” – through which all applications are entered. Once these application are submitted to the Checklister system, each one is automatically checked and verified for completeness and are then subsequently summarized in order to rapidly determine the exact status of that file, such as the acceptance or denial of a payment used in a traditional retail sales transaction or an online sales transaction.