29 CFR § 1620.20 - Pay differentials claimed to be based on extra duties.
Additional duties may not be a defense to the payment of higher wages to one sex where the higher pay is not related to the extra duties. The Commission will scrutinize such a defense to determine whether it is bona fide. For example, an employer cannot successfully assert an extra duties defense where:
(a) Employees of the higher paid sex receive the higher pay without doing the extra work;
(b) Members of the lower paid sex also perform extra duties requiring equal skill, effort, and responsibility;
(c) The proffered extra duties do not in fact exist;
(d) The extra task consumes a minimal amount of time and is of peripheral importance; or
(e) Third persons (i.e., individuals who are not in the two groups of employees being compared) who do the extra task as their primary job are paid less than the members of the higher paid sex for whom there is an attempt to justify the pay differential.