Common components

The header and trailer every message carries, and the party group that identifies the client on order-entry and drop-copy messages.

StandardHeader

TAG	NAME	TYPE	REQ	DESCRIPTION
8	BeginString	string	Y	Must be set to FIXT.1.1. Since FIX version 5.0, this field represents the session version. The application version gets specified in Logon message's DefaultApplVerID (1137) tag.
9	BodyLength	int	Y	Message length in bytes up to the checksum field; must be the second field in message.
35	MsgType	string	Y	The type of message proceeding the header; must be the third field in the message. Supported values include: Administrative (all sessions) A: Logon j: BusinessReject 0: Heartbeat 1: TestRequest 2: ResendRequest 3: Reject 4: SequenceReset 5: Logout Order Entry D: NewOrderSingle G: OrderCancelReplaceRequest F: OrderCancelRequest 9: OrderCancelReject Market Data x: SecurityListRequest y: SecurityList BK: SecurityListUpdateReport V: MarketDataRequest Y: MarketDataRequestReject W: MarketDataSnapshotFullRefresh X: MarketDataIncrementalRefresh
49	SenderCompID	string	Y	Value chosen by the user used to identify sending session.
56	TargetCompID	string	Y	Value assigned by the exchange.
34	MsgSeqNum	int	Y	Monotonically increasing sequence number.
43	PossDupFlag	boolean	C	Indicates possible retransmission of a message: N: Original Transmission Y: Possible duplicate
97	PossResend	char	C	Indicates whether the message may have already been sent with a different sequence number. Useful when performing a replay: N: Original transmission Y: Possible resend
52	SendingTime	utc timestamp	Y	Time the message was transmitted, expressed in UTC, microseconds: YYYYMMDD-HH:MM:SS.ssssss.

StandardTrailer

TAG	NAME	TYPE	REQ	DESCRIPTION
10	CheckSum	string	Y	Three-byte checksum calculated by summing every byte in the message up to and not including the checksum field itself. This value is then moduloed by 256 and written with prefixed 0s (if necessary) to meet the 3-byte requirement.

Parties

TAG	NAME	TYPE	REQ	DESCRIPTION
453	NoPartyIDs	int	Y	Number of PartyID (448), PartyIDSource (447), and PartyRole (452) entries. This tag must be the first entry before the repeating group(s). Must be set equal to 1. Only one party is supported per request.
↳448	PartyID	string	Y	Start of a new party group entry. Party identifier/code.
↳452	PartyRole	int	Y	Identifies the type or role of the PartyID (448) specified: 3: Client ID

Next: Order entry, the messages you send to place, amend and cancel orders.