The perception and calculation of depreciation is an issue with tax implications. The terms under which such issue is settled are reflected in the ordinary use durations, in the depreciation regimes opposable to economic agents, implicitly in the deductibility degree of depreciation in establishing the taxable income and the value considered upon depreciation calculation. From the fiscal viewpoint, decentralization in establishing the use duration imposes au authorized control that should moderate the company policy in establishing reduced use durations, and, implicitly, reduced durations of asset depreciation. The durations applied by companies must be fiscally approved. The depreciation durations approved by the tax authorities are in most cases fiscal durations, which differ from accounting durations.