FIX Specification

Version 1.0.4

Supported Message Types

Message	MsgType	Description
Logon	A	Sent by FIX client to authenticate and establish the FIX session
Heartbeat	0	Sent by either client or server at preset interval within the working FIX session
Test Request	1	Sent to force a heartbeat from the opposing application
Resend Request	2	To request retransmission of messages which were missed
Reject	3	Response to a message that could not be processed
Sequence Reset	4	To reset the FIX session sequence number
Logout	5	To safely disconnect the connected FIX session
New Order - Single	D	To submit a new single order
Execution Report	8	Sent whenever the state of the order changes
Order Cancel Request	F	To request cancellation of an order
Order Cancel/Replace Request	G	To request modification of an order
Order Cancel Reject	9	Sent if the Order Cancel Request (F) or Order Cancel/Replace Request (G) could not be executed

Message Header

All messages should contain the following tags in the header:

Tag	Field	Mandatory	Description
8	BeginString	Y	FIX.4.2
9	BodyLength	Y	Size of the message body in bytes
34	MsgSeqNum	Y	Message sequence number
35	MsgType	Y	Message type, should be one of the types supported in this doc
49	SenderCompID	Y	Provided by Alpaca, must be present in all FIX messages. This will be returned as TargetCompID (56) in all FIX messages to clients
52	SendingTime	Y	UTC timestamp of message transmission. Precision supported: Millis, Micros, Nanos
56	TargetCompID	Y	Provided by Alpaca, must be present in all FIX messages. This will be returned as SenderCompID (49) in all FIX messages to clients

Message Trailer

All messages should contain the following tags in the trailer:

Tag	Field	Mandatory	Description
10	CheckSum	Y	Last field in the messages with trailing `<SOH>`. Value calculated by the FIX engine from message data

Logon (A)

Tag	Field	Mandatory	Description
35	MsgType	Y	A - For Logon
98	EncryptMethod	Y	0 - None, only accepted value
108	HeartBtInt	Y	Must be set to `30` for 30 seconds
141	ResetSeqNumFlag	N	Y - Resets both sender and target sequence number to 1

Example FIX Message

|8=FIX.4.2|9=73|35=A|34=1|49=SENDER|52=20240524-16:02:42.003|56=ALPACA|98=0|108=30|141=Y|10=131|

Heartbeat (0)

Sent by either client or server if no message has been received since the last heartbeat interval. This is also sent in response to a Test Request (1).

Tag	Field	Mandatory	Description
35	MsgType	Y	0 - For Heartbeat
112	TestReqID	N	Required only when Heartbeat is sent in response to a Test Request (1)

Example FIX Message

|8=FIX.4.2|9=91|35=0|49=SENDER|56=ALPACA|34=2|52=20230330-16:52:321.029|10=049|

Test Request (1)

May be sent by either client or server, to force a Heartbeat (0) from the other party.

Tag	Field	Mandatory	Description
35	MsgType	Y	1 - For Test Request
112	TestReqID	Y	Identifier to be returned in the resulting Heartbeat (0)

Example FIX Message

|8=FIX.4.2|9=91|35=1|49=SENDER|56=ALPACA|34=2|52=20230330-16:52:321.029|112=TEST|10=049|

Resend Request (2)

Sent to request retransmission of messages which were missed.

Tag	Field	Mandatory	Description
35	MsgType	Y	2 - For Resend Request
7	BeginSeqNo	Y	Beginning sequence number of requested messages
16	EndSeqNo	Y	Ending sequence number of requested messages

Example FIX Message

|8=FIX.4.2|9=66|7=9|16=36|34=12|35=2|49=SENDER|52=20230627-14:10:21.769|56=ALPACA|10=126|

Reject (3)

Sent when a message is rejected or cannot be processed by the FIX server.

Tag	Field	Mandatory	Description
35	MsgType	Y	3 - For Reject
45	RefSeqNum	Y	Sequence number of the rejected message
58	Text	N	Reason for rejection
371	RefTagID	N	The tag number of the FIX field being referenced
372	RefMsgType	N	The MsgType (35) of the FIX message being referenced
373	SessionRejectReason	N	Reject reason codes. 0 - Invalid tag number 1 - Required tag missing 2 - Tag not defined for this message type 3 - Unsupported Message Type 4 - Tag specified without a value 5 - Value is incorrect (out of range) for this tag 6 - Incorrect data format for value 9 - CompID problem 10 - SendingTime accuracy problem 11 - Invalid MsgType

Example FIX Message

|8=FIX.4.2|9=0134|35=3|34=44196|49=ALPACA|56=TARGET|52=20230330-20:18:38.039|58=0005 Tag specified without a value|45=44196|371=11|372=8|373=4|10=092|

Sequence Reset (4)

Sent to reset the incoming sequence number on the other side. The sequence reset should be used only to increase the sequence number. Any request to decrease the sequence number will result in a Reject (3) message.

Tag	Field	Mandatory	Description
35	MsgType	Y	4 - For Sequence Reset
36	NewSeqNo	Y	New sequence number
123	GapFillFlag	N	N - Sequence reset to recover from an out-of-sequence condition, MsgSeqNum(34) is ignored Y - Gap fill message, MsgSeqNum(34) field must be valid

Example FIX Message

|8=FIX.4.2|9=61|34=12|35=4|36=9|49=SENDER|52=20230627-14:14:51.732|56=ALPACA|10=156|

Logout (5)

May be sent by either client or server, to terminate the session. The other party would respond with a confirming Logout message as an acknowledgement.

Tag	Field	Mandatory	Description
35	MsgType	Y	5 - For Logout

Example FIX Message

|8=FIX.4.2|9=56|34=12|35=5|49=SENDER|52=20230627-14:16:50.690|56=ALPACA|10=197|

New Order - Single (D)

Sent by the client to submit a new single order.

Tag	Field	Mandatory	Description
35	MsgType	Y	D - For New Order - Single
1	Account	Y	Account number
11	ClOrdID	Y	Unique identifier of the order assigned by the client (must be no longer than 48 characters)
12	Commission	N	Commission to collect from the account holder
13	CommType	N	1 - per share 2 - percentage, 5% should be represented as .05 3 - absolute
18	ExecInst	N	1 - Not held 5 - Held
21	HandlInst	Y	1 - Automated execution with no broker intervention, only accepted value
38	OrderQty	N	Number of shares to trade, required if CashOrderQty (152) is not set
40	OrdType	Y	1 - Market 2 - Limit 3 - Stop 4 - Stop limit 5 - Market on close B - Limit on close
44	Price	N	Required for Limit `40=2` and Stop Limit `40=4` orders
54	Side	Y	1 - Buy 2 - Sell
55	Symbol	Y	Ticker symbol
59	TimeInForce	Y	0 - Day (day) 1 - Good Till Cancel (gtc) 2 - At the Opening (opg) 3 - Immediate or Cancel (ioc) 4 - Fill or Kill (fok) 7 - At the Close (cls)
60	TransactTime	Y	UTC timestamp of order creation by client
77	OpenClose	N	Indicates whether the resulting position from the trade would be an opening or closing position. O - Open C - Close
99	StopPx	N	Required for Stop `40=3` and Stop Limit `40=4` orders
109	ClientID	N	Sub-account tag for omnibus accounts
152	CashOrderQty	N	Notional value to trade, required if OrderQty (38) is not set
336	TradingSessionID	N	8 - Extended Hours Required for extended hours orders only

Example FIX Messages

|8=FIX.4.2|9=139|1=TEST_ACCOUNT|11=c5bfc5f6-163d-450e-bb4a-fb25188cde8e|34=12|35=D|38=10|40=1|49=SENDER|52=20230613-14:01:37.330|54=1|55=SPY|56=ALPACA|59=1|10=030|

|8=FIX.4.2|9=141|1=TEST_ACCOUNT|11=c5bfc5f6-163d-450e-bb4a-fb25188cde8e|34=12|35=D|40=1|49=SENDER|52=20230613-14:43:47.572|54=1|55=SPY|56=ALPACA|59=0|152=100|10=130|

|8=FIX.4.2|9=149|1=TEST_ACCOUNT|11=c5bfc5f6-163d-450e-bb4a-fb25188cde8e|34=12|35=D|38=10|40=2|44=350.78|49=SENDER|52=20230613-14:45:58.303|54=1|55=SPY|56=ALPACA|59=0|10=005|

|8=FIX.4.2|9=149|1=TEST_ACCOUNT|11=c5bfc5f6-163d-450e-bb4a-fb25188cde8e|34=12|35=D|38=10|40=3|49=SENDER|52=20230613-14:50:51.223|54=1|55=SPY|56=ALPACA|59=0|99=350.78|10=006|

|8=FIX.4.2|9=159|1=TEST_ACCOUNT|11=c5bfc5f6-163d-450e-bb4a-fb25188cde8e|34=12|35=D|38=10|40=4|44=350.78|49=SENDER|52=20230613-15:26:35.992|54=1|55=SPY|56=ALPACA|59=0|99=350.78|10=246|

|8=FIX.4.2|9=149|1=TEST_ACCOUNT|11=c5bfc5f6-163d-450e-bb4a-fb25188cde8e|34=12|35=D|38=10|40=2|44=350.78|49=SENDER|52=20230613-14:45:58.303|54=1|55=SPY|56=ALPACA|59=5|10=005|

Execution Report (8)

Sent by the server whenever an order receives an update. Each execution report contains field OrdStatus (39) which is used to convey the current status of the order as understood by Alpaca, as well as fields ExecType (150) and ExecTransType (20) which describe the purpose of the message.

Tag	Field	Mandatory	Description
35	MsgType	Y	8 - For Execution Report
1	Account	Y	Account number
6	AvgPx	Y	Average price of all fills on this order
11	ClOrdID	Y	Unique identifier of the order as assigned by the client
12	Commission	N	Monetary commission value charged on a fill/partial fill
14	CumQty	Y	Filled quantity on the order
15	Currency	N	Account base currency, default USD
17	ExecID	Y	Unique identifier of the execution assigned by Alpaca
19	ExecRefID	N	ExecID (17) of the original execution being canceled or corrected when `20=1` or `20=2`
20	ExecTransType	Y	Transaction type. 0 - New 1 - Cancel 2 - Correct 3 - Status, for Restated (D) message upon stop trigger
30	LastMkt	N	Market of execution for this fill
31	LastPx	N	Price of this fill
32	LastShares	N	Quantity traded on this fill
37	OrderID	Y	Unique identifier of the order assigned by Alpaca
38	OrderQty	N	Either CashOrderQty (152) or OrderQty (38) is provided
39	OrdStatus	Y	Identifies current status of order. 0 - New 1 - Partially filled 2 - Filled 3 - Done for day 4 - Canceled 5 - Replaced 6 - Pending Cancel 8 - Rejected A - Pending New C - Expired E - Pending Replace
40	OrdType	N	Same as specified on the order. 1 - Market 2 - Limit 3 - Stop 4 - Stop limit 5 - Market on close B - Limit on close
41	OrigClOrdID	N	ClOrdID (11) of the original order in cancel and cancel/replace requests
44	Price	N	Sent when specified on the order
54	Side	Y	1 - Buy 2 - Sell
55	Symbol	Y	Ticker symbol
58	Text	N	Contains reject reason when `150=8`
59	TimeInForce	N	Same as specified on the order. 0 - Day (day) 1 - Good Till Cancel (gtc) 2 - At the Opening (opg) 3 - Immediate or Cancel (ioc) 4 - Fill or Kill (fok) 7 - At the Close (cls)
60	TransactTime	N	Server time in UTC when execution occurred, nanoseconds precision
99	StopPx	N	Sent when specified on the order
150	ExecType	Y	Describes the type of execution report. 0 - New 1 - Partial fill 2 - Fill 3 - Done for day 4 - Canceled 5 - Replaced 6 - Pending Cancel, ack for Order Cancel Request (F) 8 - Rejected A - Pending New C - Expired D - Restated, for stop price triggers E - Pending Replace, ack for Order Cancel/Replace Request (G)
151	LeavesQty	Y	Unfilled quantity on the order. When order is closed (filled, done for day, canceled, replaced, rejected, expired) value could be 0
152	CashOrderQty	N	Either CashOrderQty (152) or OrderQty (38) is provided. Specifies the notional amount conveyed on the order
378	ExecRestatementReason	N	Populated when ExecType (150) = Restated (D). 100 - Stop triggered, for stop and stop limit orders

Example FIX Messages

|8=FIX.4.2|9=216|1=TEST_ACCOUNT|17=694bc450-3ca6-461e-8566-f977dcec9e2d|34=12|35=8|37=c5bfc5f6-163d-450e-bb4a-fb25188cde8e|39=A|40=1|49=ALPACA|52=20230615-18:14:29.702|54=1|55=SPY|56=SENDER|59=0|60=20230615-18:14:29.702|150=A|151=10|10=088|

|8=FIX.4.2|9=216|1=TEST_ACCOUNT|17=694bc450-3ca6-461e-8566-f977dcec9e2d|34=12|35=8|37=c5bfc5f6-163d-450e-bb4a-fb25188cde8e|39=0|40=1|49=ALPACA|52=20230615-18:14:45.263|54=1|55=SPY|56=SENDER|59=0|60=20230615-18:14:45.263|150=0|151=10|10=054|

|8=FIX.4.2|9=251|1=TEST_ACCOUNT|6=350.78|14=5|15=USD|17=694bc450-3ca6-461e-8566-f977dcec9e2d|31=350.78|32=5|34=12|35=8|37=c5bfc5f6-163d-450e-bb4a-fb25188cde8e|39=1|40=1|49=ALPACA|52=20230615-18:15:00.622|54=1|55=SPY|56=SENDER|59=0|60=20230615-18:15:00.622|150=1|151=5|10=185|

|8=FIX.4.2|9=253|1=TEST_ACCOUNT|6=350.78|14=10|15=USD|17=694bc450-3ca6-461e-8566-f977dcec9e2d|31=350.78|32=10|34=12|35=8|37=c5bfc5f6-163d-450e-bb4a-fb25188cde8e|39=2|40=1|49=ALPACA|52=20230615-18:15:21.920|54=1|55=SPY|56=SENDER|59=0|60=20230615-18:15:21.920|150=2|151=0|10=024|

|8=FIX.4.2|9=216|1=TEST_ACCOUNT|17=694bc450-3ca6-461e-8566-f977dcec9e2d|34=12|35=8|37=c5bfc5f6-163d-450e-bb4a-fb25188cde8e|39=E|40=1|49=ALPACA|52=20230615-18:26:53.971|54=1|55=SPY|56=SENDER|59=0|60=20230615-18:26:53.971|150=E|151=10|10=112|

|8=FIX.4.2|9=256|1=TEST_ACCOUNT|17=694bc450-3ca6-461e-8566-f977dcec9e2d|34=12|35=8|37=c5bfc5f6-163d-450e-bb4a-fb25188cde8e|39=5|40=1|41=56fcd203-7a97-430d-b14c-b0d9a7f59f2f|49=ALPACA|52=20230615-18:15:38.108|54=1|55=SPY|56=SENDER|59=0|60=20230615-18:15:38.108|150=5|151=10|10=144|

|8=FIX.4.2|9=216|1=TEST_ACCOUNT|17=694bc450-3ca6-461e-8566-f977dcec9e2d|34=12|35=8|37=c5bfc5f6-163d-450e-bb4a-fb25188cde8e|39=6|40=1|49=ALPACA|52=20230615-18:24:50.191|54=1|55=SPY|56=SENDER|59=0|60=20230615-18:24:50.191|150=6|151=10|10=060|

|8=FIX.4.2|9=216|1=TEST_ACCOUNT|17=694bc450-3ca6-461e-8566-f977dcec9e2d|34=12|35=8|37=c5bfc5f6-163d-450e-bb4a-fb25188cde8e|39=4|40=1|49=ALPACA|52=20230615-18:17:45.813|54=1|55=SPY|56=SENDER|59=0|60=20230615-18:17:45.813|150=4|151=10|10=070|

|8=FIX.4.2|9=227|1=TEST_ACCOUNT|17=694bc450-3ca6-461e-8566-f977dcec9e2d|34=12|35=8|37=c5bfc5f6-163d-450e-bb4a-fb25188cde8e|39=8|40=1|49=ALPACA|52=20230615-18:15:51.825|54=1|55=SPY|56=SENDER|59=0|60=20230615-18:15:51.825|103=Price too low|150=8|10=191|

Order Cancel Request (F)

Sent by the client to request cancellation of an order.

Tag	Field	Mandatory	Description
35	MsgType	Y	F - For Order Cancel Request
1	Account	Y	Account number
11	ClOrdID	Y	Unique identifier of cancel request assigned by the client
41	OrigClOrdID	Y	ClOrdID (11) of the order to be canceled as assigned by the client
54	Side	Y	As specified on the order to be canceled
55	Symbol	Y	As specified on the order to be canceled
60	TransactTime	Y	UTC timestamp when cancel request was initiated

To acknowledge this message, an Execution Report (8) with 150=6 is sent immediately followed by an Execution Report (8) with 150=4 or an Order Cancel Reject (9) message. Sometimes an Order Cancel Reject (9) message might be sent directly without sending an Execution Report (8) with 150=6.

Example FIX Messages

|8=FIX.4.2|9=190|35=F|34=5|49=SENDER|52=20240524-16:02:44.709|56=ALPACA|1=account1|11=b165965d-0c9d-467e-a174-ee30f3fe6dbe|41=b5db0b8e-bbc1-4906-aff8-c58d18ba3398|54=1|55=AAPL|60=20240524-16:02:44.709206406|10=226|

Order Cancel/Replace Request (G)

Sent by the client to request modification of an order.

Tag	Field	Mandatory	Description
35	MsgType	Y	G - For Order Cancel/Replace Request
1	Account	Y	Account number
11	ClOrdID	Y	Unique identifier of the replacement order assigned by the client (must be no longer than 48 characters)
21	HandlInst	Y	1 - Automated execution with no broker intervention, only accepted value
38	OrderQty	N	Modified quantity for the order
40	OrdType	Y	As specified on the original order
41	OrigClOrdID	Y	ClOrdID (11) of the order to be modified as assigned by the client
44	Price	N	Modified price for the order
54	Side	Y	As specified on the original order
55	Symbol	Y	As specified on the original order
59	TimeInForce	N	Modified time in force for the order
60	TransactTime	Y	UTC timestamp when cancel/replace request was initiated
99	StopPx	N	Modified stop price for the order

Example FIX Messages

|8=FIX.4.2|9=212|35=G|34=21|49=SENDER|52=20240524-16:16:58.956|56=ALPACA|1=account1|11=45169819-088a-4089-9758-f28e830e95f0|21=3|40=2|41=f001f209-2c3e-42e3-9ab1-10e74ee39fe5|44=1.50000|54=1|55=AAPL|60=20240524-16:16:58.956849295|10=173|

Order Cancel Reject (9)

Sent by the server if the Order Cancel Request (F) or Order Cancel/Replace Request (G) message could not be honored. Some common reject scenarios include:

when order is already filled or closed
when a previous Order Cancel Request (F) or Order Cancel/Replace Request (G) is pending for this order

Tag	Field	Mandatory	Description
35	MsgType	Y	9 - For Order Cancel Reject
1	Account	Y	Account number
11	ClOrdID	Y	Unique identifier of cancel or cancel/replace request as assigned by the client
37	OrderID	Y	Unique identifier of the order as assigned by Alpaca for which the cancel or cancel/replace request was rejected
39	OrdStatus	Y	Order status after this cancel reject is applied
41	OrigClOrdID	Y	ClOrdID (11) of the order for which the cancel or cancel/replace request was rejected
58	Text	N	Reject reason
60	TransactTime	N	Server time in UTC when cancel or replace reject occurred
102	CxlRejReason	N	Code to identify reason for cancel rejection. 0 - Too late to cancel 1 - Unknown order 2 - Broker Option 3 - Order already in Pending Cancel or Pending Replace status
434	CxlRejResponseTo	Y	1 - Response to Order Cancel Request (F) 2 - Response to Order Cancel/Replace Request (G)

Example FIX Messages

|8=FIX.4.2|9=220|35=9|34=18|49=ALPACA|52=20240524-16:02:46.215|56=SENDER|1=account1|11=a7860828-4dc5-4f8f-bfb1-8fbca8855c88|37=f50af678-bba4-44ea-9b23-0fc452ed4921|39=6|41=2c017b79-a843-4146-a2b7-3bf83af89482|58=TOO_LATE_TO_CANCEL|434=1|10=116|

|8=FIX.4.2|9=198|35=9|34=45|49=ALPACA|52=20240524-16:16:59.085|56=SENDER|1=account1|11=5cdf9082-067b-4497-a90c-f5e8c666409b|37=UNKNOWN|39=8|41=c7feaf5a-54d2-458d-8ab2-9b2f337a28ec|58=replace pending for order|434=2|10=179|

Version History

Version	Date	Change
0.1.0	08/05/2024	Document Creation
0.1.1	24/05/2024	Changed FIX version to FIX.4.2 Removed ApplVerID (1128) from Message Header Added ClOrdID (11) and OrigClOrdID (41) as required in Order Cancel Request (F) and Order Cancel/Replace Request (G) Removed OrderID (37) from Order Cancel Request (F) and Order Cancel/Replace Request (G) Added OrderQty (38) to Order Cancel/Replace Request (G) Updated FIX examples
0.1.2	12/06/2024	Removed Account (1) and RawData (96) from Logon (A) message Added RefTagID (371), RefMsgType (372) and SessionRejectReason (373) to Reject (3) message Added HandlInst (21), TransactTime (60) and OpenClose (77) to New Order - Single (D) Added 1 (per share) as an accepted value for CommType (13) in New Order - Single (D) Updated AvgPx (6) to mandatory in Execution Report (8) Added Commission (12), ExecRefID (19), ExecTransType (20), LastMkt (30), OrderQty (38) and CashOrderQty (152) to Execution Report (8) Removed OrdRejReason (103) from Execution Report (8) Updated possible values for ExecType (150) in Execution Report (8)
1.0.0	13/06/2024	Added Side (54), Symbol (55) and TransactTime (60) to Order Cancel Request (F) Added OrderID (37) to Order Cancel Reject (9) Added HandlInst (21), OrdType (40), Side (54), Symbol (55) and TransactTime (60) to Order Cancel/Replace Request (G)
1.0.1	04/09/2024	Added Market on close (5) and Limit on close (B) as values for OrdType (40) on New Order - Single (D) Added At the Close (7) as a value for TimeInForce (59) on New Order - Single (D)
1.0.2	08/10/2024	Added Restated (D) as value for ExecType (150) on Execution Report (8) Added ExecRestatementReason (378) to Execution Report (8) Added Status (3) as value for ExecTransType (20) on Execution Report (8) Added TransactTime (60) to Order Cancel Reject (9)
1.0.3	14/01/2025	Added Good Till Crossing (5) as a value for TimeInForce (59) on New Order - Single (D) Added ClientID (109) to New Order - Single (D)
1.0.4	03/04/2025	Removed Good Till Crossing (5) as a valid value for TimeInForce (59) on New Order - Single (D) Added TradingSessionID (336) to New Order - Single (D)