As I understand it you have entered a contract to purchase at as near as price as possible. The same as when you hold over night and the price gaps lower than your stop. Unless it is a guaranteed stop then you get out at the nearest price which would be the opening price nad get hit for the difference, I can understand this with stops however if you bid a price which is under market then the order simply shouldn't be filled. It wouldn't be in the true market. I had a look in their pds and couldn't find it stated anywhere (but it maybe there somewhere).
You definately shouldn't get your bid price when the stock gaps up. If this was allowable trading would be a piece of cake with stocks such as bhp and rio.
Be careful about any comments re CMC.
Their reputation is lousy and much worse than IG but each have their own good and bad experiences. There have been numerous comparisons between all the providers and a google search will bring these up.
Let us know if IG can point you to the info in their pdf somewhere. If not in their pdf then I can't see how they can execute the trade.
