The reject message should be issued when a message is received but cannot be properly processed due to a session-level rule violation. An example of when a reject may be appropriate would be the receipt of a message with invalid basic data (e.g. MsgType=&) which successfully passes de-encryption, CheckSum and BodyLength checks. As a rule, messages should be forwarded to the trading application for business level rejections whenever possible.
Rejected messages should be logged and the incoming sequence number incremented.
Note: The receiving application should disregard any message that is garbled, cannot be parsed or fails a data integrity check. Processing of the next valid FIX message will cause detection of a sequence gap and a Resend Request will be generated. Logic should be included in the FIX engine to recognize the possible infinite resend loop, which may be encountered in this situation.
Generation and receipt of a Reject message indicates a serious error that may be the result of faulty logic in either the sending or receiving application.
If the sending application chooses to retransmit the rejected message, it should be assigned a new sequence number and sent with PossResend=Y.
Whenever possible, it is strongly recommended that the cause of the failure be described in the Text field (e.g. INVALID DATA - FIELD 35).
If an application-level message received fulfills session-level rules, it should then be processed at a business message-level. If this processing detects a rule violation, a business-level reject should be issued. Many business-level messages have specific "reject" messages, which should be used. All others can be rejected at a business-level via the Business Message Reject message. See Volume 1: "Business Message Reject" message.
Note that in the event a business message is received, fulfills session-level rules, however, the message cannot be communicated to the business-level processing system, a Business Message Reject with BusinessRejectReason = "Application not available at this time" should be issued.
The '^' character is used to represent SOH character.