FIX Error InvalidMsgType: Invalid message type
What this error means
An invalid MsgType error occurs when tag 35 (MsgType) contains a value that is not recognized in the FIX specification or is not supported by the counterparty. Common examples include typos, unsupported message types, version mismatches, or corrupted message type fields.
Common causes
Common causes include:
1) Typo in MsgType value during message construction,
2) Using message type not supported by counterparty,
3) FIX version mismatch (message type exists in different version),
4) Custom message types not recognized by receiving party,
5) Message type field corrupted during transmission,
6) Incorrect message type for the FIX version in use.
Example log snippet
8=FIX.4.4|9=100|35=Z|49=CLIENT|56=EXCHANGE|34=5|52=20231116-10:30:00|10=123|
How to fix it
1) Verify MsgType value is correct (D=NewOrderSingle, 8=ExecutionReport, 3=Reject, etc.)
2) Check counterparty supports the message type you're sending
3) Verify FIX version compatibility - ensure message type exists in your FIX version
4) Use standard FIX message types from the specification
5) Validate MsgType before sending messages
6) Review message construction code for typos or incorrect assignments
7) Check for message corruption during transmission
Related Knowledge Articles
Analyze Your FIX Logs
Upload or paste your FIX logs to automatically detect this error and get detailed diagnostics.
Analyze FIX Logs