Subject to regulation 18, a person who sells pre-basic seed potatoes, basic seed potatoes, certified seed potatoes or test and trial seed potatoes must issue to the buyer not later than 14 days after the sale or, if the seed potatoes are not delivered at the time of sale, not later than 14 days after delivery, a sale note, delivery note, invoice or similar document specifying in relation to the seed potatoes the particulars specified in Schedule 7.