Md. Code Ann., State Fin. & Proc. § 17-215
(a) Each contractor and subcontractor subject to this subtitle shall pay each employee not less than the prevailing wage rate required under this subtitle:
(3) except as provided in subsection (b) of this section, without deductions for:
(b) A contractor or subcontractor may make deductions that are:
(3) contained in a written agreement between an employee and an employer undertaken at the beginning of employment, if the agreement:
Added by Acts 1988, c. 48, § 2, eff. Oct. 1, 1988.