What is and why do we need a Fault Contract? Well, if the days of ASMX based web services there was no built-in way to report exceptions back to the client. For the most part, the only way a client found out something was wrong was that the call to the web service timed out. There was no other explanation. This was a tremendous source of frustration for client developers, and also prompted many a developer and architect to pull their hair out over the prospect of reporting some sort of exception information back to the client. A lot of developers, myself included, broke out the duct tape, chewing gum and bailing wire and attempted to build some sort of notification mechanism that would not leave the clients hanging (no pun intended). These solutions ranged from complicated to outrageously complicated. All met with limited success. WCF introduced the concept of a Fault Contract.