Faults can be of four basic types: VersionMismatch, MustUnderstand, Client and Server: VersionMismatch: invalid namespace for the SOAP Envelope MustUnderstand: a required header was not understood by the server Client: the message sent by the client was not properly formed, or did not contain the necessary information to fulfill the request. Server: the message could not be processed Faults can also contain other information, such as a basic message describing the fault, the URI of the originator of the fault, and a detail field that can be used to provide additional information on the fault.