1. The reimbursement of an overpayment of benefits is the responsibility of the beneficiary unit that received the benefits during the year in which the overpayment was created. In cases where there is a change in the composition of the beneficiary unit following a separation as of fact or law and the benefits were paid separately to the head and the spouse, the overpayment shall remain the joint responsibility of the adult members of the beneficiary unit, proportionate to the amount of the benefits that was paid to each respectively.