§ 412.
(a)
Taxable years prior to 1978
For the purposes of determining average monthly wage and quarters of coverage the amount of self-employment income derived during any taxable year which begins before 1978 shall—
(1)
in the case of a taxable year which is a calendar year, be credited equally to each quarter of such calendar year; and
(2)
in the case of any other taxable year, be credited equally to the calendar quarter in which such taxable year ends and to each of the next three or fewer preceding quarters any part of which is in such taxable year.
(b)
Taxable years after 1977
Except as provided in subsection (c), for the purposes of determining average indexed monthly earnings, average monthly wage, and quarters of coverage the amount of self-employment income derived during any taxable year which begins after 1977 shall—
(1)
in the case of a taxable year which is a calendar year or which begins with or during a calendar year and ends with or during such year, be credited to such calendar year; and
(2)
in the case of any other taxable year, be allocated proportionately to the two calendar years, portions of which are included within such taxable year, on the basis of the number of months in each such calendar year which are included completely within the taxable year.
For purposes of clause (2), the calendar month in which a taxable year ends shall be treated as included completely within that taxable year.
([Aug. 14, 1935, ch. 531], title II, § 212, as added [Aug. 28, 1950, ch. 809], title I, § 104(a), [64 Stat. 492], 504; amended [Pub. L. 95–216, title III, § 351(b)], Dec. 20, 1977, [91 Stat. 1549]; [Pub. L. 110–234, title XV, § 15352(b)(3)], May 22, 2008, [122 Stat. 1526]; [Pub. L. 110–246, § 4(a)], title XV, § 15352(b)(3), June 18, 2008, [122 Stat. 1664], 2288.)