(a) Services performed after 1938 and before 1955 constitute employment under section 3306(c) if such services were employment under the law applicable to the period in which they were performed.

(b) The tax applies with respect to remuneration paid by an employer after 1954 for services performed after 1938 and before 1955, as well as for services performed after 1954, to the extent that the remuneration and services constitute wages and employment. See §§31.3306(b)-1 to 31.3306(b)(8)-1, inclusive, relating to wages.

(c) Determination of whether services performed after 1938 and before 1955 constitute employment shall be made in accordance with the provisions of law applicable to the period in which they were performed and of the regulations thereunder. The regulations applicable in determining whether services performed after 1938 and before 1955 constitute employment are as follows:

(1) Services performed in 1939—26 CFR (1939) Part 400 (Regulations 90).

(2) Services performed after 1939 and before 1955—26 CFR (1939) Part 403 (Regulations 107).