Error Handling

Overview

Margin FIX uses standard FIX error messages with additional detail in the Text field. Errors fall into two categories:

Session-level errors: Protocol violations, handled with Reject (35=3)
Business-level errors: Application logic issues, handled with BusinessMessageReject (35=j) or order-specific rejection messages

Error Message Types

Reject (35=3)

Used for session-level protocol violations.

Tag	Name	Description	Required
45	RefSeqNum	Sequence number of rejected message	Yes
58	Text	Human-readable error description	No
371	RefTagID	Tag that caused the rejection	No
372	RefMsgType	Message type being rejected	No
373	SessionRejectReason	Rejection reason code	No

Session Reject Reasons (373)

Code	Reason	Description
0	Invalid tag number	Unknown tag in message
1	Required tag missing	Mandatory field not present
2	Tag not defined for message	Tag not valid for this message type
3	Undefined tag	Tag number not in FIX specification
4	Tag without value	Empty tag value
5	Incorrect value	Invalid value for tag
6	Incorrect data format	Wrong data type
8	Signature problem	Authentication failure
9	CompID problem	SenderCompID/TargetCompID issue
10	SendingTime accuracy	SendingTime must be within 30 seconds of server time
11	Invalid MsgType	Unknown message type

BusinessMessageReject (35=j)

Used for application-level business logic errors.

Tag	Name	Description	Required
45	RefSeqNum	Sequence number of rejected message	Yes
58	Text	Human-readable error description	No
372	RefMsgType	Message type being rejected	Yes
379	BusinessRejectRefID	Business ID from rejected message	No
380	BusinessRejectReason	Business rejection reason code	Yes

Business Reject Reasons (380)

Code	Reason	Description
0	Other	See Text field
1	Unknown ID	Referenced ID not found
2	Unknown Security	Invalid symbol
3	Unsupported Message Type	Message type not implemented on this margin session
4	Application not available	System temporarily unavailable
5	Conditionally required field missing	Context-specific field missing

Order-Specific Rejections

Order Reject Reasons (103)

In ExecutionReport (35=8) with ExecType=Rejected:

Code	Reason	Common Causes
1	Unknown symbol	Invalid margin market ticker
2	Exchange closed	Trading paused or unavailable
3	Order exceeds limit	Risk limit breach or insufficient margin
4	Too late to enter	Market not accepting new orders
5	Stale order	Expired timestamp on request
6	Duplicate order	ClOrdID already used
11	Unsupported order characteristic	Invalid order parameters
13	Incorrect quantity	Invalid order size
15	Unknown account	Subaccount not found or permission denied
99	Other	See Text field

Cancel Reject Reasons (102)

In OrderCancelReject (35=9):

Code	Reason	Description
0	Too late to cancel	Order already filled
1	Unknown order	Order not found or identifiers do not match
99	Other	See Text field

Common Error Scenarios

Example: Invalid Tag

// Sent
8=FIXT.1.1|35=D|11=123|38=10|333333=test|...

// Response: Reject
8=FIXT.1.1|35=3|45=5|58=Undefined tag received|371=333333|372=D|373=3|

Example: Order Rejected by Exchange

// Sent
8=FIXT.1.1|35=D|11=456|38=10|55=BTC-PERP|44=19.5000|...

// Response: ExecutionReport (Rejected)
8=FIXT.1.1|35=8|11=456|150=8|39=8|58=EXCHANGE_PAUSED|103=2|...

Order-entry failures returned by the exchange are sent as ExecutionReport (35=8) with ExecType=Rejected, not as BusinessMessageReject. BusinessMessageReject (35=j) is used for application-layer failures before normal exchange rejection handling, such as rate limiting or listener-session restrictions.

Example: Insufficient Balance

// Response: ExecutionReport
8=FIXT.1.1|35=8|11=789|150=8|39=8|58=INSUFFICIENT_BALANCE|103=3|...

Troubleshooting

MsgSeqNum Too High on Logon

Symptom: Logon fails or the server sends a ResendRequest for messages the client doesn’t have. Cause: The client is sending a MsgSeqNum higher than what the server last saw. This typically happens when the client’s local sequence store persists across sessions but the server has reset (e.g. after maintenance or a prior ResetSeqNumFlag=Y logon). Fix:

KalshiNR, KalshiDC: Set ResetSeqNumFlag<141>=Y on every Logon. These sessions require it; Logon will be rejected without it.
KalshiRT: If you don’t need to recover missed messages, set ResetSeqNumFlag<141>=Y to reset both sides to 1. If you do need retransmission continuity, ensure your local sequence store matches the server’s state.

If using QuickFIX, set ResetOnLogon=Y in your session config for non-retransmission sessions.

SendingTime Rejected

Symptom: Reject (35=3) with SessionRejectReason<373>=10. Cause: The client’s clock is more than 30 seconds off from the server. Sync your system clock via NTP.

Duplicate Session (“already exists”)

Symptom: Logout (35=5) immediately after Logon with Text<58>="already exists". Cause: Another FIX connection is already active with the same API key and TargetCompID. Only one connection is allowed per API key per session type. This can also occur if a previous connection was not cleanly closed and the server hasn’t yet detected the disconnect. Fix: Ensure the previous session is fully disconnected before reconnecting. If the prior connection was lost unexpectedly, wait for the server’s heartbeat timeout to expire (up to 60 seconds depending on your HeartbeatInt setting) before retrying. Use separate API keys for concurrent connections.

Logon Signature Rejected

Symptom: Logout immediately after Logon with a signature error. Cause: The SendingTime used in the pre-hash string doesn’t match the SendingTime<52> in the actual Logon message. If using a FIX library, the library may auto-populate SendingTime. Use that exact value when computing the signature, not a separately generated timestamp.

Overview

REST

WebSockets

FIX

Overview

Error Message Types

Reject (35=3)

Session Reject Reasons (373)

BusinessMessageReject (35=j)

Business Reject Reasons (380)

Order-Specific Rejections

Order Reject Reasons (103)

Cancel Reject Reasons (102)

Common Error Scenarios

Troubleshooting

MsgSeqNum Too High on Logon

SendingTime Rejected

Duplicate Session (“already exists”)

Logon Signature Rejected

​Overview

​Error Message Types

​Reject (35=3)

​Session Reject Reasons (373)

​BusinessMessageReject (35=j)

​Business Reject Reasons (380)

​Order-Specific Rejections

​Order Reject Reasons (103)

​Cancel Reject Reasons (102)

​Common Error Scenarios

​Troubleshooting

​MsgSeqNum Too High on Logon

​SendingTime Rejected

​Duplicate Session (“already exists”)

​Logon Signature Rejected

Overview

Error Message Types

Reject (35=3)

Session Reject Reasons (373)

BusinessMessageReject (35=j)

Business Reject Reasons (380)

Order-Specific Rejections

Order Reject Reasons (103)

Cancel Reject Reasons (102)

Common Error Scenarios

Troubleshooting

MsgSeqNum Too High on Logon

SendingTime Rejected

Duplicate Session (“already exists”)

Logon Signature Rejected