Quote from IBj:
Official Response:
IB's policy regarding busts is as follows:
If an exchange calls and requests a bust, IB ALWAYS says 'no'. This is for the benefit of our clients. You can assume nobody calls and asks to break a trade where they are the winner (i.e. the IB client is a loser). The exchanges then send the trades to a rulings committee which may decide to force the cancellation. The exchange then calls us back and reports if the trade has been ruled a mistrade, in which case we report it onward to the client.
If an IB customer requests a trade cancellation, we call the exchange. We never evaluate whether the request is reasonable or success in the getting a cancellation is likely, although we may provide the IB trader an indication based on our previous experience. Nevertheless, we always pass the request through.
If there are IB clients on both sides of the trade, many exchanges (especially ECN's) will back away from the evaluation process and force IB to make the decision. IB's policy is to follow the exchange's posted or practiced guidelines to the extent possible, i.e. we try to substitute an equivalent decision making process. Our policy is posted on our website under the ContactUs/Service/ErroneousTrade menupoint. Please note, we do not want to be in the decision making position. However exchanges occasionally force us into that role because it gets this messy issue off their plate (at least that is my personal view).
What we DON'T do:
We do not evaluate cancellation decisions based on how good the customer is.
We do not filter IB client requests
This may not be 100% complete, but it covers the main points.