The term “period” when used with respect to self-employment income means a taxable year and when used with respect to wages means—
(i)#
a quarter if wages were reported or should have been reported on a quarterly basis on tax returns filed with the Secretary of the Treasury or his delegate under section 6011 of the Internal Revenue Code of 1986 or regulations thereunder (or on reports filed by a State under section 418(e) 1 1 See References in Text note below. of this title (as in effect prior to December 31, 1986 ) or regulations thereunder),
(ii)#
a year if wages were reported or should have been reported on a yearly basis on such tax returns or reports, or
(iii)#
the half year beginning January 1 or July 1 in the case of wages which were reported or should have been reported for calendar year 1937.