(a) Taxable years beginning before September 13, 1966, and ending after September 12, 1966—(1) General rule. An election made under section 615(e) or section 617(a) applies only to expenditures paid or incurred after September 12, 1966. The income tax treatment of exploration expenditures paid or incurred before September 13, 1966, will be determined in accordance with the provisions of section 615 prior to its amendment by the Act of September 12, 1966 (Pub. L. 89-570, 80 Stat. 759). If a taxpayer makes an election under section 615(e) in his income tax return for a taxable year beginning before September 13, 1966, and ending after September 12, 1966, amounts deducted under section 615 with respect to expenditures paid or incurred during such taxable year but before September 13, 1966, will be taken into account in determining whether the $100,000 limitation set forth in section 615(a) is reached during 1966. Similarly, a taxpayer making an election under section 615(e) shall take into account expenditures deducted under section 615 for periods prior to September 13, 1966, in determining when the $400,000 overall limitation set forth in section 615(c) is reached. The fact that a taxpayer deducts under section 615 expenditures paid or incurred prior to September 13, 1966, shall not affect his right to make an election under section 617(a) to deduct under section 617 expenditures paid or incurred after September 12, 1966.

(2) Allocation in case of inadequate records. If a taxpayer pays or incurs exploration expenditures during a taxable year beginning before September 13, 1966, and ending after September 12, 1966, but his records as to any mine or property are inadequate to permit a determination of the amount paid or incurred during the portion of the year ending after September 12, 1966, and the amount paid or incurred on or before such date, the exploration expenditures as to which the records are inadequate paid or incurred with respect to the mine or property during the taxable year shall be allocated to each part year (that is, the part occurring before September 13, 1966, and the part occurring after September 12, 1966) in the ratio which the number of days in such part year bears the number of days in the entire taxable year. For example, if the records of a calendar year taxpayer for 1966 are inadequate to permit a determination of the amount of exploration expenditures paid or incurred with respect to a certain mine or property after September 12, 1966, and the amount paid or incurred before September 13, 1966, 255⁄365 of the total exploration expenditures paid or incurred by the taxpayer with respect to the mine or property during 1966 shall be allocated to the period beginning January 1, 1966, and ending September 12, 1966, and 110⁄365 of the total exploration expenditures paid or incurred with respect to the mine or property during 1966 shall be allocated to the period beginning September 13, 1966, and ending December 31, 1966.

(3) Partnership elections. With respect to exploration expenditures paid or incurred by a partnership before September 13, 1966, the option to deduct under section 615(a) and the election to defer under section 615(b) shall be made by the partnership, rather than by the individual partners. All elections under sections 615(e), 617(a), or 617(b) as to the tax treatment of a partner's distributive share of exploration expenditures paid or incurred by any partnership of which he is a member shall be made by the individual partner, rather than by the partnership.

(b) Effect of transfer of mineral property. The binding effect of a taxpayer's election under section 615(e) shall not be affected by his receiving property with respect to which deductions have been allowed under section 617(a). The binding effect of a taxpayer's election under section 617(a) shall not be affected by his receiving property with respect to which deductions have been allowed under section 615 pursuant to an election made under section 615(e). However, see section 615(g)(2) for rules under which amounts deducted under section 615 by a transferor may be subject to recapture in the hands of a transferee who has made an election under section 617(a).