I am trying to come up with some ideas for a cake for someone who just paid off their credit card debt....I need a simple design, nothing complicated. any help is appreciated.

red "paid in full stamp"

Haha YES! That will be perfect! and make sure to put lots of sugar confetti all over the cake. That calls for a huge celebration. Even a champagne bottle or marini glasses for celebration should go on the cake. Small sugar pieces made out of gum paste. I like the idea of the red "paid in full" stamp with some sugar confetti.

zero balance

Those are all great ideas guys!! thanks