FIX Error Codes – Complete Index of FIX Protocol Errors

This index provides detailed explanations for common FIX protocol errors, reject codes, and troubleshooting steps. Each error page includes root causes, broker-side vs client-side actions, and how to resolve the issue.

Missing Mandatory Tags

Tag 371 Missing ClOrdID

ClOrdID (tag 11) is required but missing from order messages

Missing Side (54)

Side field required for order submission

Missing Symbol (55)

Symbol field required for trading

Missing OrderQty (38)

Order quantity required for new orders

FIX Reject Codes

Reject 102 – Too Late to Cancel

Order cancellation rejected because order is already filled or canceled

Reject 103 – Invalid Price

Price value outside acceptable range or invalid format

Reject 5 – Invalid Tag Number

Tag number not recognized in FIX specification

Reject 6 – Required Tag Missing

Mandatory tag absent from message

Sequence & Session Issues

FIX Gap Fill Issue

Sequence number gaps detected in FIX session

Sequence Reset Required

Sequence numbers out of sync, reset needed

Duplicate MsgSeqNum

Message sequence number already received

Invalid Values

Invalid Tag Value

Tag value doesn't match expected format or enum

Invalid MsgType

Message type not recognized or invalid

Invalid Timestamp (52)

SendingTime format incorrect or timezone issue

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FIX Error Codes – Complete Index