I've seen a number of posts expressing criticism about the idea of money being taxed more than once, often in discussions about whether the inheritance tax is unfair because the government is taxing the money when it is income to the wage earner, and when it passes to the earner's heirs upon his or her death.

Maybe I'm missing something here, but doesn't the government routinely tax money "more than once"? For example, the money I earn through working is initially subject to a number of different taxes (income, social security, etc.). My after-tax income is taxed again when I go out and spend it on a variety of items. For example, if I buy a car with my already-taxed earnings, I have to pay state and federal taxes on my purchase, so that same money has now been taxed twice. Same thing if I use the money to buy anything from baseball tickets to a house. It's taxed coming in and going out, so to speak.

So, tell me, where does the idea come from that money can only being taxed once?