A transaction in which interest is not paid on interest there is no compounding. For example, if you deposit $1,000 in an account that pays 5% a year simple interest, you would receive $50 interest in year one and another $50 in year two. If interest were compounded annually, you would receive $52.50 in year two. All deposit accounts compound interest, however, because if they didn't, depositors would shuffle accounts between banks. In my example, you could withdraw the $1050 at the end of year one, put it into another bank, and earn $52.50 in year two.