If I place an order to buy or sell a stock or futures contract through a regular retail brokerage, is there any sort of personal identifier that goes to the exchange along with my order? I don't necessarily mean my name or SSN, but just any sort of identifier that is unique to me.

So if I buy 1067 shares of a stock at 9:37 am, and then later that day I place a stop order to sell those 1067 shares, would the exchange know the stop order was placed by the same person who bought the shares at 9:37 am?

Edit: On my broker's Level II quotes, it has columns for Ex (name of exchange, e.g. NSDQ, EDGX, ARCA, PHLX, NYSE, etc.), Bid/Ask, and Bid Size/Ask Size. I noticed that if I submit a buy limit order, the Level II quotes show my bid with my account number in the "Ex" field. I wonder if my account number is being sent to the exchange along with my order?

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    Are you placing these trades through a regular retail brokerage, or are you placing these trades using direct market access? Not all orders go to a public exchange. Which country are you in? – Flux Aug 4 '20 at 18:52
  • I can't source it but my recollection is that your broker tags the order with an identification code so that if the order is filled, he knows what account to attribute it to. Out of curiosity, why would you be concerned if the exchange or ECN knew that it was your stop order? – Bob Baerker Aug 5 '20 at 16:14
  • @BobBaerker I wouldn't want anyone to get an idea of what my pain points are based on the orders I submit. – 7529 Aug 13 '20 at 1:35

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