For UK shares providers will price their bid and offer using the price of the share in the underlying market. The company’s spread is then added around the underlying market bid/offer to create what they refer to as ‘our quote’. On a day-to-day basis the difference between a provider’s bid and the underlying market bid will remain the same as will the difference between the offer prices. If the underlying market bid/offer spread widens/narrows then the spread betting provider’s quote will widen/narrow with it. Providers derive future individual share prices (quarterly markets) by taking the underlying market price and adding the cost of carry from the trade date until the expiry date.