1) Retail perk 
An off-invoice cash discount from a list or suggested resale price 
[n] - a discount from the list price of a commodity allowed by a manufacturer or wholesaler to a merchant
noun a discount from the list price of a commodity allowed by a manufacturer or wholesaler to a merchant
Discounts given to regular customers, which are not usually recorded in books.
A trade discount is the reduction in price a?manufacturer?or wholesaler gives a wholesaler or retail when they buy a product or group of products. In other words, a trade discount is a certain percentage a manufacturer is willing to reduce its list price for wholesalers or retailers.