At the same time of fixed account (i.e., on a straight line basis) is charged as a depreciation expenses so that it eliminates the asset or brings it down to its salvage or scrap value, as the case may be. The important point to be noted is that the amount of depreciation to be charged every year must be so calculated as to reduce that asset together with interest accumulated thereon to its salvage value at the end of the useful life of the asset. Such a calculation, if done manually, would be very difficult. Hence the figures of depreciation are obtained form Annuity tables. As the yearly interest diminishes while the depreciation charge is the same, the net charge to revenue increases annually.