Intangible assets
Intangible assets acquired separately from a business combination (including purchased patents, know-how, trademarks, licences and distribution rights) are initially measured at cost. The cost of intangible assets acquired in a material business combination (referred to as acquisition intangibles) is the fair value as at the date of acquisition. Following initial recognition, intangible assets are carried at cost less any accumulated amortisation and any accumulated impairment losses. All intangible assets are amortised on a straight-line basis over their estimated useful economic lives. The estimated useful economic life of an intangible asset ranges between three and 20 years depending on its nature. Internally-generated intangible assets are expensed in the income statement as incurred. Purchased computer software and certain costs of information technology projects are capitalised as intangible assets. Software that is integral to computer hardware is capitalised as plant and equipment.