You deposit your money into a savings account for a reason, right? So you can earn interest on your money. People also earn interest from lending money to people. We’re not talking about you lending your buddy Dave a couple bucks to buy lunch; we’re talking about lending lots of money so the interest really accumulates on the loan. Well, add up all that interest you accumulate and there’s your interest income. Not to burst your bubble, but that interest income is all fully taxable.