Mass. Gen. Laws ch. 149 § 105A
"Comparable work", work that is substantially similar in that it requires substantially similar skill, effort and responsibility and is performed under similar working conditions; provided, however, that a job title or job description alone shall not determine comparability.
"Working conditions", shall include the environmental and other similar circumstances customarily taken into consideration in setting salary or wages, including, but not limited to, reasonable shift differentials, and the physical surroundings and hazards encountered by employees performing a job.
"Wages", shall include all forms of remuneration for employment.
An employer who is paying a wage differential in violation of this section shall not reduce the wages of any employee solely in order to comply with this section.
An employer who violates this section shall be liable to the employee affected in the amount of the employee's unpaid wages, and in an additional equal amount of liquidated damages. Action to recover such liability may be maintained in any court of competent jurisdiction by any 1 or more employees for and on their own behalf, or on behalf of other employees similarly situated. Any agreement between the employer and any employee to work for less than the wage to which the employee is entitled under this section shall not be a defense to an action. An employee's previous wage or salary history shall not be a defense to an action. The court shall, in addition to any judgment awarded to the plaintiff, award reasonable attorneys' fees to be paid by the defendant and the costs of the action.
The attorney general may also bring an action to collect unpaid wages on behalf of 1 or more employees, as well as an additional equal amount of liquidated damages, together with the costs of the action and reasonable attorneys' fees. Such costs and attorneys' fees shall be paid to the commonwealth. The attorney general shall not be required to pay any filing fee or other cost in connection with such action.
If an employee recovers unpaid wages under this section and also files a complaint or brings an action under 29 U.S.C. section 206 (d) which results in an additional recovery under federal law for the same violation, the employee shall return to the employer the amounts recovered under this section, or the amounts recovered under federal law, whichever is less.
Any action based upon or arising under sections 105A to 105C, inclusive, shall be instituted within 3 years after the date of the alleged violation. For the purposes of this section, a violation occurs when a discriminatory compensation decision or other practice is adopted, when an employee becomes subject to a discriminatory compensation decision or other practice or when an employee is affected by application of a discriminatory compensation decision or practice, including each time wages are paid, resulting in whole or in part from such a decision or practice.
Notwithstanding the requirements of section 5 of chapter 151B, a plaintiff shall not be required to file a charge of discrimination with the Massachusetts commission against discrimination as a prerequisite to bringing an action under this section.
No employer shall contract with an employee to avoid complying with this subsection, or by any other means exempt itself from this subsection; provided, however, that an employer may prohibit a human resources employee, a supervisor, or any other employee whose job responsibilities require or allow access to other employees' compensation information, from disclosing such information without prior written consent from the employee whose information is sought or requested, unless the compensation information is a public record as defined in clause 26 of section 7 of chapter 4.
This subsection shall be enforced in the same manner as subsection (b); provided, however, that an action based on a violation of clause (2) of this subsection may be brought by or on behalf of 1 or more applicants for employment; and provided, further, that in any action brought under this subsection, the plaintiff may also recover any damages incurred.
An employer who has completed a self-evaluation in good faith within the previous 3 years and prior to the commencement of the action, and can demonstrate that reasonable progress has been made towards eliminating wage differentials based on gender for comparable work in accordance with that evaluation, but cannot demonstrate that the evaluation was reasonable in detail and scope, shall not be entitled to an affirmative defense, but shall not be liable for liquidated damages under this section.
Evidence of a self-evaluation or remedial steps undertaken in accordance with this subsection shall not be admissible in any proceeding as evidence of a violation of this section or section 4 of chapter 151B that occurred prior to the date the self-evaluation was completed or that occurred either (i) within 6 months thereafter or (ii) within 2 years thereafter if the employer can demonstrate that it has developed and begun implementing in good faith a plan to address any wage differentials based on gender for comparable work.
An employer who has not completed a self-evaluation shall not be subject to any negative or adverse inference as a result of not having completed a self-evaluation.
Mass. Gen. Laws ch. 149, § 105A