(a) In general. Subsection (d) of the Act provides the basis adjustments required to be made by the taxpayer as of the 1956 adjustment date in respect of all periods before that date in order to determine the adjusted basis of all retirement-straight line property held by the taxpayer on that date. This adjusted basis on the 1956 adjustment date shall be used by the taxpayer for all purposes of the Code for any taxable year beginning after December 31, 1955. In order to arrive at the adjusted basis on the 1956 adjustment date, the taxpayer shall start with the unadjusted basis of all retirement-straight line property held on the changeover date by the taxpayer or a predecessor and shall, with respect to both the asset and reserve accounts, (1) make the adjustments prescribed by this section and subsection (d) of the Act and (2) also make those adjustments required, in accordance with the method of accounting regularly used, for those additions, retirements, and other dispositions of property which occurred on or after the changeover date and before the taxpayer's 1956 adjustment date. For an illustration of adjustments required in accordance with the method of accounting regularly used, see paragraph (e)(3) of this section. The adjustments required by subsection (d) of the Act shall be made in lieu of the adjustments for depreciation otherwise required by section 1016(a) (2) and (3) of the Code. The adjustments required by subsection (d) of the Act are set forth in paragraphs (b), (c), and (d) of this section.

(b) Adjustment for depreciation sustained before March 1, 1913—(1) In general. Subsection (d)(1) of the Act requires an adjustment to be made as of the 1956 adjustment date for depreciation sustained before March 1, 1913, on all retirement-straight line property held on March 1, 1913, by the taxpayer or a predecessor for which cost was or is claimed as basis and which was either (i) retired before the changeover date by the taxpayer or a predecessor or (ii) held on the changeover date by the taxpayer or a predecessor. This adjustment for depreciation sustained before March 1, 1913, shall be made in accordance with the conditions and limitations described in subparagraphs (2) and (3) of this paragraph and shall be allocated, in the manner prescribed in subparagraph (4) of this paragraph, among all retirement-straight line property held by the taxpayer on its 1956 adjustment date. The term “cost”, when used in this paragraph with reference to the basis of property, shall be construed to mean the amount paid for the property or, if that amount could not be determined, then such other amount as was accepted by the Commissioner as “cost” for basis purposes.

(2) Depreciation sustained on property retired before the changeover date. Pursuant to subsection (d)(1)(A) of the Act, an adjustment to the basis of retirement-straight line property held by the taxpayer on its 1956 adjustment date shall be made as of that date for depreciation sustained before March 1, 1913, on all retirement-straight line property held on March 1, 1913, by the taxpayer or a predecessor for which cost was claimed as the basis and which was retired before the changeover date by the taxpayer or a predecessor, except that:

(i) The adjustment shall be made only if a deduction was allowed in computing net income by reason of the retirement and the deduction so allowed was computed on the basis of the cost of the property unadjusted for depreciation sustained before March 1, 1913, and

(ii) In the case of any such property retired during any taxable year beginning after December 31, 1929, the adjustment shall not exceed that portion of the amount attributable to depreciation sustained before March 1, 1913, which resulted, by reason of the deduction so allowed, in a reduction of taxes under the Code or under prior income, war-profits or excess-profits tax laws.

(3) Depreciation sustained on property held on the changeover date. Pursuant to subsection (d)(1)(B) of the Act, an adjustment to the basis of retirement-straight line property held by the taxpayer on its 1956 adjustment date shall be made as of that date for depreciation sustained before March 1, 1913, on all retirement-straight line property held on March 1, 1913, by the taxpayer or a predecessor for which cost was or is claimed as basis and which was held on the changeover date by the taxpayer or a predecessor. This subparagraph shall not apply, however, to any such property which (i) was disposed of on or after the changeover date by reason of sale, casualty, or abnormal retirement in the nature of special obsolescence, and (ii) is property to which paragraph (c) of this section and subsection (d)(2) of the Act apply.

(4) Manner of allocating adjustment. Pursuant to subsection (d)(1) of the Act, the amount of the adjustment required under this paragraph for depreciation sustained before March 1, 1913, which is attributable to a particular kind or class of retirement-straight line property held by the taxpayer on its 1956 adjustment date shall be made with respect to that kind or class of such property. If the adjustment required under this paragraph for depreciation sustained before March 1, 1913, is attributable to retirement-straight property of a particular kind or class no longer held by the taxpayer on its 1956 adjustment date, then the part of the adjustment to be allocated to any retirement-straight line property held by the taxpayer on its 1956 adjustment date shall be that amount which bears the same ratio to the adjustment as the unadjusted basis of the property so held bears to the entire unadjusted basis of all retirement-straight line property held by the taxpayer on its 1956 adjustment date.

(c) Adjustment for part of terms-letter reserve applicable to property disposed of on or after changeover date and before 1956 adjustment date. Pursuant to subsection (d)(2) of the Act, an adjustment to the basis of retirement-straight line property held by the taxpayer on its 1956 adjustment date shall be made as of that date for that part of the terms-letter reserve which was applicable to any retirement-straight line property disposed of by sale, casualty, or abnormal retirement in the nature of special obsolescence, but only if the sale occurred in, or a deduction by reason of such casualty or abnormal retirement was allowed for Federal income-tax purposes for a period on or after the changeover date and before the taxpayer's 1956 adjustment date. This paragraph shall apply even though, in computing the adjusted basis of the property for purposes of determining gain or loss on the sale, casualty, or abnormal retirement, the basis of the retirement-straight line property was not reduced by the part of the terms-letter reserve applicable to the property. If necessary, the adjustment required by this paragraph shall be allocated, in the manner prescribed in paragraph (b)(4) of this section, among all retirement-straight line property held by the taxpayer on its 1956 adjustment date.

(d) Adjustment for depreciation allowable under the terms-letter for periods on and after the changeover date and before the 1956 adjustment date. Pursuant to subsection (d)(3) of the Act, an adjustment to the basis of retirement-straight line property held by the taxpayer on its 1956 adjustment date shall be made as of that date for the entire amount of depreciation allowable under the terms-letter for all periods on and after the changeover date and before the taxpayer's 1956 adjustment date. This adjustment shall include all such depreciation allowable with respect to any retirement-straight line property which was disposed of on or after the changeover date and before the 1956 adjustment date.

(e) Illustration of basis adjustments required for taxable years beginning on or after the 1956 adjustment date. The application of this section may be illustrated by the following example, which is based upon the assumption that multiple asset accounts are used: