Demystifying FIX Rejections
Rejections are an often poorly understood aspect of the FIX Protocol. They manifest in a variety of ways. Some are a normal part of trading, while others represent serious problems. Even worse, some are effectively invisible to trading platforms (OMS/EMS), requiring raw FIX troubleshooting to address.
The 35=3 session-level rejections are often invisible to trading systems. 35=j “business” rejections are rarely handled with any consistency. It pays to know the basics of rejecting in FIX if you’re a member of operations, trade support, or development!