When a TP determines that it should not process a particular conversation it has accepted, the TP can reject the conversation by calling the Reject_Conversation service. For example, a TP might reject a conversation if it determines that the conversation has an unsupported sync_level. When it rejects a conversation, the TP communicates the reason for the rejection to its partner by specifying a sense code as an input parameter to the Reject_Conversation service. The partner LU resolves the sense code to a return code that it passes it to the partner TP.

The Reject_Conversation service must be used early in a transaction; that is, before any communication activity has occurred (such as data being sent or received).