(a) Authorization
A taxpayer may use the method provided in subsection (b) (whether or not such method has been prescribed under section 471) in inventorying goods specified in an application to use such method filed at such time and in such manner as the Secretary may prescribe. The change to, and the use of, such method shall be in accordance with such regulations as the Secretary may prescribe as necessary in order that the use of such method may clearly reflect income.

(b) Method applicable
In inventorying goods specified in the application described in subsection (a), the taxpayer shall:

(1) Treat those remaining on hand at the close of the taxable year as being: First, those included in the opening inventory of the taxable year (in the order of acquisition) to the extent thereof; and second, those acquired in the taxable year;

(2) Inventory them at cost; and

(3) Treat those included in the opening inventory of the taxable year in which such method is first used as having been acquired at the same time and determine their cost by the average cost method.

(c) Condition
Subsection (a) shall apply only if the taxpayer establishes to the satisfaction of the Secretary that the taxpayer has used no procedure other than that specified in paragraphs (1) and (3) of subsection (b) in inventorying such goods to ascertain the income, profit, or loss of the first taxable year for which the method described in subsection (b) is to be used, for the purpose of a report or statement covering such taxable year—

(1) to shareholders, partners, or other proprietors, or to beneficiaries, or

(2) for credit purposes.

(d) 3-year averaging for increases in inventory value
The beginning inventory for the first taxable year for which the method described in subsection (b) is used shall be valued at cost. Any change in the inventory amount resulting from the application of the preceding sentence shall be taken into account ratably in each of the 3 taxable years beginning with the first taxable year for which the method described in subsection (b) is first used.

(e) Subsequent inventories
If a taxpayer, having complied with subsection (a), uses the method described in subsection (b) for any taxable year, then such method shall be used in all subsequent taxable years unless—

(1) with the approval of the Secretary a change to a different method is authorized; or,

(2) the Secretary determines that the taxpayer has used for any such subsequent taxable year some procedure other than that specified in paragraph (1) of subsection (b) in inventorying the goods specified in the application to ascertain the income, profit, or loss of such subsequent taxable year for the purpose of a report or statement covering such taxable year (A) to shareholders, partners, or other proprietors, or beneficiaries, or (B) for credit purposes; and requires a change to a method different from that prescribed in subsection (b) beginning with such subsequent taxable year or any taxable year thereafter.

If paragraph (1) or (2) of this subsection applies, the change to, and the use of, the different method shall be in accordance with such regulations as the Secretary may prescribe as necessary in order that the use of such method may clearly reflect income.

(f) Use of government price indexes in pricing inventory
The Secretary shall prescribe regulations permitting the use of suitable published governmental indexes in such manner and circumstances as determined by the Secretary for purposes of the method described in subsection (b).

(g) Conformity rules applied on controlled group basis

(1) In general
Except as otherwise provided in regulations, all members of the same group of financially related corporations shall be treated as 1 taxpayer for purposes of subsections (c) and (e)(2).

(2) Group of financially related corporations
For purposes of paragraph (1), the term "group of financially related corporations" means—

(A) any affiliated group as defined in section 1504 determined by substituting "50 percent" for "80 percent" each place it appears in section 1504(a) and without regard to section 1504(b), and

(B) any other group of corporations which consolidate or combine for purposes of financial statements.