Skin: The Human B... The Integumentary... PB 5.1 Layers of the Ski... Skin (Inte The terms on an invoice are 4/15, n/30. This means that Oa. a discount of 15% will be allowed if payment is made by the 4" day after the date of the invoice. Ob. a discount of 4% will be allowed if payment is made within 15 days from the date of the invoice. Oc. a discount of 4% will be allowed if payment is made by the 15th of the month. Od. a discount of 15% will be allowed if payment is made with 4 days from the date of the invoice