An intangible asset is a non-physical asset having a useful life greater than one year. If an intangible asset is determined to have a useful life, then its book value is amortized over that useful life. If at any point there is judged to be a decline in the remaining value of an intangible asset below its carrying amount, then the difference is recognized as an impairment expense in the current period; that is, the impairment charge is not spread out over a number of periods.