Template:Set off capsule
One does not exercise a set-off right willy nilly. Unless one is, mutually, settlement netting (where on a given day I owe you a sum, you owe me a sum, and we agree to settle by one of us paying the other the difference) set-off is a drastic remedy which will be seen as enemy action. You would not do it, without agreement, to any client you expected to keep. So, generally, use set-off as a remedy it only arises following an event of default.