What is a previous discount? 3
This is basically a discount you get after paying the retail price. For example. Send your receipt to the manufacturer and you will receive a check for 50.
Retro active discount
As noted by both respondents, a retroactive discount is a discount given by the seller after payment of the goods.
This is very common in licensed businesses, where the tenant rents out the brewery's property and attaches it to the property. The tenant agrees to pay the regular bill, but then he receives a return check from time to time (monthly, quarterly or annually) depending on how many cages he has purchased in each case.
Discount applies after purchase (refund).