Very long, I know, but trust me you will probably learn something very valuable that could save you lots of money. Read on... I usually get good fills on my stop-losses but today I got horrible exit sell prices on both of my trades. This is what happened on both of my trades : I was watching price go below my stop-loss price and my order did not trigger. Prices where staying near and below my stop-loss price and then went further down without my stop-loss ever being filled. Eventually it did get filled a big 0.10-11$ cents below ! I usually get out at 0.01-0.03$ from my stop price. It's not like prices crashed and I got hurt because of slippage, no it's just seems the order was not being executed. I contacted IB's tech support by chat and big surprise the guy said it was a normal execution (yeah, right...). I have looked at the T&S and noticed there was plenty of time for my order to get filled at a better price since prices stayed just below my stop price long enough. After more than an hour, the tech guy told me it was normal my stop was not triggered before because of the way the default stop trigger behavior is handled for NASDAQ stocks. Default behavior : http://www.interactivebrokers.com/php/webhelp/webhelp.htm#Making_Trades/trigger.htm For NASDAQ stocks (NMS, Small Cap, OTC) and US options, the default trigger method is the double bid/ask method, where two consecutive ask price (bid price) values must be less than (greater than) or equal to the trigger price, and the second bid or ask must have greater size if it is at the same price level as the first bid or ask. For CASH contracts, the default trigger method is bid/ask, where the ask price (bid price) value must be less than (greater than) or equal to the trigger price. For all other contracts, the default trigger method is the Last method, described below. ---- Seems like LAST price was not used which would explain why my stop was not triggered ! This is all very fishy and I can't believe this happened for 2 trades today. What are the chances ? How can I prove they were responsible for my losses because of the horrible & abnormal fills ?