The Illinois Equal Pay Act, which prohibits employers from discriminating against employees in terms of compensation on the basis of gender, has been amended, effective January 1, 2016, to cover all Illinois employers of any size. The Illinois Equal Pay Act makes it unlawful for an Illinois employer to pay an employee less than the employer pays to another employee of the opposite sex for the same or substantially similar work on jobs which require equal skill, effort and responsibility that are performed under similar work conditions. Prior to the amendment, the Act only applied to employers with four or more employees. The Act, which is administered and enforced by the Illinois Department of Labor, provides for civil penalties for each offense. There are exceptions, including any factor that would not constitute unlawful discrimination under the Illinois Human Rights Act.

Unequal pay on the basis of gender is also prohibited by the federal Equal Pay Act, as long as certain factors are present. The Equal Pay Act is part of the federal Fair Labor Standards Act. Wage discrimination is also unlawful under Title VII of the Civil Rights Act of 1964, as amended, based on any protected classification (not only sex), under the same legal standards as those for traditional employment discrimination claims. Despite the federal and state equal pay laws, women are still generally compensated less than men.