When sending orders to exchanges, is there any sort of personal identifier that is associated with the order?

External question — Personal Finance Stack Exchange Author: 7529 Original post: https://money.stackexchange.com/questions/129546 License: CC BY-SA 4.0 — https://creativecommons.org/licenses/by-sa/4.0/ Adaptation: HTML converted to plain text; contact email addresses removed. 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?