An assignment of wages is not valid unless: The assignment is: In writing; Signed and acknowledged by the assignor before a notary public in and for the county where he resides; and Entered the same day on the docket of the court by the clerk; and Within three days from the execution and acknowledgment of the assignment, a copy of the assignment with the certificate of acknowledgment is served on the assignor’s employer in the same manner as the Maryland Rules provide for service of a summons. An assignment of wages by a married person is not valid unless also executed and acknowledged by the assignor’s spouse in the manner required by subsection (a) of this section. An assignment of wages to be earned in whole or in part more than six months after the making of the assignment is void.