An amortized tax depreciation will gradually write off the initial cost of (an asset) over a period. One such example is straight-line depreciation which spreads the cost of an asset evenly over the time it will be used, also known as its "useful life." It requires only three inputs to calculate: asset cost, useful life and estimated salvage value - meaning, how much the asset is likely to be worth at the end of its useful life.
When there is no taxable income (i.e. lawful money is redeemed in all currency transactions) then the tax depreciations that are typically written-off and will hold no value for the person or entity unless they are refundable tax credits.