The term “period of trial work”, with respect to an individual entitled to benefits under section 423, 402(d), 402(e), or 402(f) of this title, means a period of months beginning and ending as provided in paragraphs (3) and (4).

For purposes of sections 416(i) and 423 of this title, any services rendered by an individual during a period of trial work shall be deemed not to have been rendered by such individual in determining whether his disability has ceased in a month during such period. For purposes of this subsection the term “services” means activity (whether legal or illegal) which is performed for remuneration or gain or is determined by the Commissioner of Social Security to be of a type normally performed for remuneration or gain.

A period of trial work for any individual shall begin with the month in which he becomes entitled to disability insurance benefits, or, in the case of an individual entitled to benefits under section 402(d) of this title who has attained the age of eighteen, with the month in which he becomes entitled to such benefits or the month in which he attains the age of eighteen, whichever is later, or, in the case of an individual entitled to widow’s or widower’s insurance benefits under section 402(e) or (f) of this title who became entitled to such benefits prior to attaining age 60, with the month in which such individual becomes so entitled. Notwithstanding the preceding sentence, no period of trial work may begin for any individual prior to the beginning of the month following September 1960; and no such period may begin for an individual in a period of disability of such individual in which he had a previous period of trial work.