JAMB - Commerce (2015 - No. 44)
The term 4 net 7 on an invoice means that
4% surcharge will be made unless payment is made within seven days
4% discount will be allowed on the price charged only if the good are bought within seven days
4% discount will be allowed on the price charge if payment is made after seven days
4% discount will be allowed on the price charged if payment is made price charged if payment is made price charged if payment is made within seven days.
Forklaring
The discount is allowed to encourage seller prompt payment for the goods bought by the buyer.