26  Annual Report Costs associated with maintaining computer software are recognised as an expense when incurred. Costs associated with the development and maintenance of the Law Commission website are recognised as an expense when incurred. Amortisation The carrying value of an intangible asset with a finite life is amortised on a straight-line basis over its useful life. Amortisation begins when the asset is available for use and ceases at the date that the asset is derecognised. The amortisation charge for each period is recognised in statement of financial performance. The useful lives and associated amortisation rates of the major class of intangible assets has been estimated as follows: Acquired computer software 3 years 33% Impairment of non-financial assets Property, plant and equipment and intangible assets that have a finite useful life are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount may not be recoverable. An impairment loss is recognised for the amount by which the asset�fs carrying amount exceeds its recoverable amount. The recoverable amount is the higher of an asset�fs fair value less costs to sell and v Value in use is depreciated replacement cost for an asset where the future economic benefits or service potential of the asset are not primarily dependent on the asset�fs ability to generate net cash inflows and where the Law Commission would, if deprived of the asset, replace its remaining future economic benefits or service potent If an asset�fs carrying amount exceeds its recoverable amount, the asset is impaired and the carrying amount is written down to the recoverable amount. For revalued assets the impairment loss is recognised against the revaluation reserve for that class of asset. Where that results in a debit balance in the revaluation reserve, the balance is recognised in the statement of financial performance. For assets not carried at revalued amount, the total impairment loss is recognised in the statement of financial performance. The reversal of an impairment loss on a revalued asset is credited to the revaluation reserve. However, to the extent that an impairment loss for that class of asset was previously recognised in the statement of financial performance, a reversal of the impairment loss is also recognised in the statement of financial performance.