Any person selling grapevine, fruit tree or fruit tree related ornamental nursery stock must maintain a set of accurate sales records to facilitate an audit and ensure that the proper assessment amount is paid to the department. The records must be maintained for a minimum of three years from the date of sale. At a minimum, the records must contain sequentially numbered sales invoices that clearly show the amount of assessment owed for each invoice. Sales invoices must be filed either numerically or alphabetically.