In Self-Match Prevention, how is the oldest executable order/quote chosen for deletion?

In Self-Match Prevention, how is the oldest executable order/quote chosen for deletion?

• A. Cancel the newest
• B. Cancel oldest principal - older of two executable orders/quotes is deleted from order book
• C. Cancel both
• D. Cancel the one with smaller size

Answer: (B)

Self-Match Prevention aims to stop a trader’s own orders from trading against their own quotes. When two executable orders or quotes could cross, the policy is to cancel the older of the two executable orders/quotes, removing the oldest one from the order book. This keeps the newer order in place and prevents a self-trade scenario. The “older” is determined by the time the orders were entered (timestamp) with standard tie-break rules applied. It isn’t based on size, and it doesn’t cancel both.

Self-Match Prevention aims to stop a trader’s own orders from trading against their own quotes. When two executable orders or quotes could cross, the policy is to cancel the older of the two executable orders/quotes, removing the oldest one from the order book. This keeps the newer order in place and prevents a self-trade scenario. The “older” is determined by the time the orders were entered (timestamp) with standard tie-break rules applied. It isn’t based on size, and it doesn’t cancel both.