The excess of the depletion deduction allowable under 611 over the adjusted basis of the property at the end of the tax year (determined without regard to the depletion deduction for the tax year) is an item of tax preference. a. Should a taxpayer include in the basis of a 614 property any unamoritized basis under 56 (a) (2)? b. Should the basis used for this purpose be the property's AMT basis or its regular income tax basis