The precise terms of the Will may have an impact on the position, but generally speaking, a right to occupy property would be an interest in possession, following the principle in Pearson v IRC that a present right to the present enjoyment of property is an interest in possession in that property. It is irrelevant whether the interest in possession is granted for life or for a fixed period or until a specified contingency occurs, but if the defined period expires, the express interest in possession would cease. If a Will creates an interest in possession then that interest would be an immediate post death interest, or 'IPDI' (assuming that all the conditions in section 49A of the Inheritance Tax Act 1984 (IHTA 1984) are met), and therefore IHTA 1984, s 49 would apply. IHTA 1984, s 49