Amazon is only tax-free in those states because it doesn't have any type of buildings there doing things like shipping or just data centers. That doesn't make the products tax free, only that Amazon doesn't have to charge tax for it. You are technically suppose to report the amount that wasn't taxed on your taxes so they can well...tax you for it. Don't think i've ever seen someone actually do that but i know people like you who have had to pay taxes on the stuff afterward because the state found out.
And yea that also covers if you buy something from a state with no taxes for the reason to not have to pay taxes at all.
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B8 resident lurker for 5 errrrr 6 years
Currently Playing: Mass Effect, Assassins Creed 2 (just got a 360)