I am using IB TWS. Some of my trades are multi-legged and I do not want to leg-in the trade. Is it possible to use LIMIT order for the multi-legged trade, or do I have to put LIMIT order on each leg? Or do I just have to use MARKET? Thank you for any suggestions.
Yes, read about combination orders in IB's documentation. The last I saw, if you use a combination order, IB protects you from the risk that some legs of your order execute without other legs, and I also know from using them that you can specify a limit price for the entire order instead of each individual leg.
I don't understand why IB is undertaking the risk of partial 1 leg execution? What is the purpose of this? To me, pair trading gives some opportunities that needs to be traded quite fast. When you trade correlated markets, they have to move in the same direction and if you are using limit orders, there might often be only one leg likely to be filled. It depends on the market traded, but if you trade index futures spread, I don't think it is a good idea.