We've been teaching Will about having his own money and using it for things that he wants. He and his brother receive a small allowance every week and I let them spend it, with the understanding that once it's gone, it's gone. He asked me if he could go to Target this past weekend so he could get some Pokemon cards (all the rage again!) and I said yes but he'd have to buy them himself.
So the three of us ride to Target and naturally, we must go to the Pokemon cards first. He chooses a package that's $12.99 and is pleased that his fourteen dollars will cover it. When we get to the checkout, I let him go ahead of me and the cards come to $13.80. First, he realizes that he left a dollar at home, so Mom spotted him a buck. Then he wants to know why the sticker says "$12.99" but the total at the register is different. I explained that the rest is taxes, that "Uncle Sam" charges taxes. Then that leads to a more complicated discussion about what taxes are and why we pay them. Then he wants to know who this "Uncle Sam" is and why he wants some of his money?" I explained as best as I could, and he seemed satisfied but dismayed that the "government charges kids money."
I just smiled sweetly at the teenage cashier and she smiled back as I said "Just wait til you get your first paycheck someday, Darling."