IG Spread Betting is what it says in the name – betting. IG like all bookies can decide to balance their books however they feel. They may have to bet against you to balance the books or maybe create a price that helps them. They do not have to go to the market at all with your ‘bet’. If they have a balanced book the spread will be their profit. CFD’s are however not betting as they are what it says in the name – a contract – so IG has to go to the market to fulfil the contract.