(a) Basis of property. The adjustments to the cost or other basis provided in sections 1011 and 1016 and the regulations thereunder, are applicable for the entire period since the acquisition of the property. Thus, proper adjustment to basis must be made under section 1016 for depreciation, obsolescence, amortization, and depletion for all taxable years beginning prior to January 1, 1952, although the cooperative association was exempt from tax under section 521 or corresponding provisions of prior law for such years. However, no adjustment for percentage or discovery depletion is to be made for any year during which the association was exempt from tax. If a cooperative association has made a proper election in accordance with section 1020 and the regulations prescribed thereunder with respect to a taxable year beginning before 1952 in which the association was not exempt from tax, the adjustment to basis for depreciation for such years shall be limited in accordance with the provisions of section 1016(a)(2).

(b) Amortization of bond premium. In the case of tax exempt and partially taxable bonds purchased at a premium and subject to amortization under section 171, proper adjustment to basis must be made to reflect amortization with respect to such premium from the date of acquisition of the bond. (For principles governing the method of computation, see the example in paragraph (b) of § 1.1016-9, relating to mutual savings banks, building and loan associations, and cooperative banks.) The basis of a fully taxable bond purchased at a premium shall be adjusted from the date of the election to amortize such premium in accordance with the provisions of section 171 except that no adjustment shall be allowable for such portion of the premium attributable to the period prior to the election.

(c) Amortization of mortgage premium. In the case of a mortgage acquired at a premium where the principal of such mortgage is payable in installments, adjustments to the basis for the premium must be made for all taxable years (whether or not the association was exempt from tax under section 521 during such years) in which installment payments are received. Such adjustments may be made on an individual mortgage basis or on a composite basis by reference to the average period of payments of the mortgage loans of such association. For the purpose of this adjustment, the term premium includes the excess of the acquisition value of the mortgage over its maturity value. The acquisition value of the mortgage is the cost including buying commissions, attorneys' fees, or brokerage fees, but such value does not include amounts paid for accrued interest.