Except as provided in subsections (b) and (d), there shall be allowed as a deduction in computing taxable income all expenditures paid or incurred during the taxable year for the development of a mine or other natural deposit (other than an oil or gas well) if paid or incurred after the existence of ores or minerals in commercially marketable quantities has been disclosed. This section shall not apply to expenditures for the acquisition or improvement of property of a character which is subject to the allowance for depreciation provided in section 167, but allowances for depreciation shall be considered, for purposes of this section, as expenditures.
At the election of the taxpayer, made in accordance with regulations prescribed by the Secretary, expenditures described in subsection (a) paid or incurred during the taxable year shall be treated as deferred expenses and shall be deductible on a ratable basis as the units of produced ores or minerals benefited by such expenditures are sold. In the case of such expenditures paid or incurred during the development stage of the mine or deposit, the election shall apply only with respect to the excess of such expenditures during the taxable year over the net receipts during the taxable year from the ores or minerals produced from such mine or deposit. The election under this subsection, if made, must be for the total amount of such expenditures, or the total amount of such excess, as the case may be, with respect to the mine or deposit, and shall be binding for such taxable year.
The amount of expenditures which are treated under subsection (b) as deferred expenses shall be taken into account in computing the adjusted basis of the mine or deposit, except that such amount, and the adjustments to basis provided in section 1016(a)(9), shall be disregarded in determining the adjusted basis of the property for the purpose of computing a deduction for depletion under section 611.
For election of 10-year amortization of expenditures allowable as a deduction under subsection (a), see section 59(e).