Yesterday I had a trade go wrong, and I talked to a brokerage rep. Can someone verify if what they told me is true? Here are the details. I attempted to sell 500 shares at 24.00. The entire 500 share order goes to a market maker who is on the inside bidding 200 shares at 24.14. He fills those 200 shares, and the remaining 300 shares are canceled immediately because he is only bidding 200. I don't get filled on the remaining 300 shares, even though there are bidders willing to pay 24.00 or higher. Is this the way it works? My broker told me it has nothing to do with their execution system; the market maker will immediately cancel your entire order after he fills you, even if it just 100 shares and your order is significantly higher.