No such assignment shall be binding on the employer of the assignor until a copy of the assignment and a written account, which shall conform to the requirements hereinafter stated, have been delivered to said employer. The account shall contain a statement of the balance due and of the sums of money received by the assignee, together with the date of every such payment and a statement as to whether such payment is interest, a payment on the principal, or, in case of a loan, a payment on the charge for making and securing it.
Massachusetts Legal Code