I have a spread I'd like to trade at IB. It appears that, if a spread order isn't supported natively by an exchange, then IB's standard spread limit orders just sit and waits until they can buy at the ASK and sell at the BID while meeting the limit. This isn't what I want to do since I want to add liquidity. IB offers a different order type: REL+MKT. The description matches what I'd like to do which is: "one or both legs are submitted as REL, once the first leg trades the second is submitted as MKT". The help page for this order type is here: http://www.interactivebrokers.com/en/software/tws/usersguidebook/ordertypes/relative___market.htm It says "When you select REL + MKT, the limit price field becomes inactive and the Trigger Price field requires the combo price input." I assume there's a good reason that this kind of order ticket isn't programmed so the limit price goes in a field called "limit" instead of "trigger price". Unfortunately, there are actually TWO "trigger price fields" that have to be filled in and no explanation of how they differ. I asked IB customer service and, as expected, haven't received any response to my ticket. I also created a very small trade and tested entering my limit price into both fields. It didn't seem to be doing what I wanted and I wasn't able to determine what TWS was doing from watching the order. Sometimes the order was active, sometimes is was held and monitored. It never seemed to change the displayed bid/ask of the underlying securities, even though my spread was inside the market. Maybe someone here knows whether this order type does what I want and how to use it?