The Director of Employment Development shall determine the amount of the overpayment and any assessment authorized under Section 1375.1 and shall notify the liable person of the basis of the overpayment determination. In the absence of fraud, misrepresentation, or willful nondisclosure, notice of the overpayment determination shall be served within the latest of the following periods:
(a) Not later than one year after the close of the benefit year in which the overpayment was made.
(b) Not later than six months after the date a backpay award was made.