A working Web API application, server and client. The client user employs an object to call the server Web API with the client user credential (login ID and transaction key), credit card holder name, credit card number, credit card expiration date, security code, and the amount of the purchase. The server Web API 1. Receives the call. 2. Authenticates the client user credential against the User table (Login ID and Transaction Key). 1. If authenticated successfully, validates the credit card with the CreditCard table (card number, card holder, card expiration date, security code, credit fund, on hold. 1. If the credit card is valid (not on hold) and has sufficient credit fund, generate and return the client user a randomized Authorization Code. 2. If the credit card is invalid (on hold) or has insufficient credit fund, return the client user a Decline message. 2. If not authenticated successfully, returns to the client user with Not valid user message. The client user displays the returned message.