Header and Trailer

All FIX messages must begin with header fields and end with a trailer field.

Tag	Field Name	Data Type	Req’d	Comments
8	BeginString	string	Y	Identifies beginning of new message and protocol version. Always the first field in a message. Value is FIX.4.4.
9	BodyLength	int	Y	Message length, in bytes, forward to the CheckSum `<10>` field. Always second field in message and unencrypted.
35	MsgType	string	Y	Defines message type. Always third field in message.
49	SenderCompID	int	Y	Used to identify a firm which sends the message.
56	TargetCompID	string	Y	Used to identify a receiving firm.
34	MsgSeqNum	int	Y	Integer message sequence number.
43	PosDupFlag	boolean	C	Required for retransmitted messages as a result of ResendRequest.
97	PossResend	boolean	C	Required when message may be a duplicate of another message sent under a different sequence number.
122	OrigSendingTime	timestamp	C	Required for messages sent as a result of ResendRequest. Time of original transmission in UTC.
52	SendingTime	timestamp	Y	Time of message transmission in UTC.

Tag	Field Name	Data Type	Req’d	Comments
10	CheckSum	int	Y	Simple checksum. Always defined as three characters in the last field in the message.