FIX Tag 11 – ClOrdID

ClOrdID (Client Order ID) is a unique identifier assigned by the client to identify an order. It must be unique within a trading session (or per day, depending on broker requirements). This tag is mandatory for NewOrderSingle (35=D), OrderCancelRequest (35=F), and OrderCancelReplaceRequest (35=G) messages.

Correct Usage

Generate a unique ClOrdID for each new order. Common approaches include: UUID, timestamp-based IDs, or sequential IDs with session prefix. The ClOrdID is echoed back in ExecutionReports and is used to reference orders in cancel/replace requests via OrigClOrdID (41).

Common Issues

1) Duplicate ClOrdID within same session causes rejects, 2) Missing ClOrdID triggers RefTagID=371 reject, 3) ClOrdID reused across sessions when broker requires daily uniqueness, 4) Empty or null ClOrdID value, 5) ClOrdID too long (some brokers have length limits).

Example FIX Message

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