There is a tradition of giving 10% of one's income to charity. Suppose someone receives a gift card as compensation for his work. Should that person separate 10% of the value of the gift card to charity?
What about a person who returns an item from a store for store credit? Does that credit count toward the amount from which one must tithe? Does it matter whether the item was given as a gift, purchased with his own money, or earned as compensation for working?