Refund
A transaction where a company pays a customer to stop being their customer in the hope that they will say nice things about the company to everyone they know. 

Returns
Products sold back to a store by people who do not know their clothing size or what colors they like. 

Gift Card
A lottery ticket for libertarians.

Void
A nihilistic status imposed upon transactions that have let us down.

Coupon
An enchanted document that casts a Decrease Cost spell when activated. Coupon generated attacks are effective against Line Items and Subtotals. Some advanced coupons can have an area of effect that targets groups of items on a receipt. Although powerful under ideal circumstances, coupon spells are vulnerable to Exceptions buffs and Expiration Date curses.

Loyalty Program 
An oath taken by a person to provide private information to a corporation in exchange for it providing notifications about limited time deals on kitchen cleaners and hot dogs.

Receipt
Proof that you purchased whipped cream, mini marshmallows, hand lotion, a bottle of Reyes de Oro tequila, and a 3-pack of Ramtex condoms at a gas station way on the other side of the freeway, 4 hours before you got home that night.

Card Reader
The final barrier between your filthy habits and the new white sectional sofa that is on sale.