Equal Pay Act of 1963 - EPA - 29 U.S. Code Chapter 8 § 206(d)

The Equal Pay Act (part of the Fair Labor Standards Act) prohibits wage discrimination by employers and labor organizations based solely on sex.
(d) Prohibition of sex discrimination
    (1) No employer having employees subject to any provisions
        of this section shall discriminate, within any establishment
        in which such employees are employed, between employees
        on the basis of sex by paying wages to employees in such
        establishment at a rate less than the rate at which he pays
        wages to employees of the opposite sex in such establishment
        for equal work on jobs the performance of which requires
        equal skill, effort, and responsibility, and which are 
        performed under similar working conditions, except where 
        such payment is made pursuant to
        (i) a seniority system;
        (ii) a merit system;
        (iii) a system which measures earnings by quantity or quality
              of production; or
        (iv) a differential based on any other factor other than sex: 
             Provided, That an employer who is paying a wage rate
             differential in violation of this subsection shall not,
             in order to comply with the provisions of this subsection,
             reduce the wage rate of any employee.
            (2) No labor organization, or its agents, representing
                employees of an employer having employees subject to
                any provisions of this section shall cause or attempt
                to cause such an employer to discriminate against an
                employee in violation of paragraph (1) of this subsection.
            (3) For purposes of administration and enforcement, any amounts
                owing to any employee which have been withheld in violation
                of this subsection shall be deemed to be unpaid minimum
                wages or unpaid overtime compensation under this chapter.
            (4) As used in this subsection, the term “labor organization� 
                means any organization of any kind, or any agency or
                employee representation committee or plan, in which employees
                participate and which exists for the purpose, in whole or in
                part, of dealing with employers concerning grievances, labor
                disputes, wages, rates of pay, hours of employment, or
                conditions of work.

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