I am completing a capital gains tax report for my father who was renting a property during the full time he owned it. He purchased this off his son (this was the sons main residential home at the time) and has now sold it to me his other son. When completing the calculation do we use the market value or the actual purchase price/ selling price. Also please could you tell me ways in which to find a historical valuation for the house if we are to use the market value?