In the US, you're supposed to claim the sales taxes for all of your out-of-state online purposes every year. There's a supplement to your tax forms where you ca

In the US, you're supposed to claim the sales taxes for all of your out-of-state online purposes every year. There's a supplement to your tax forms where you can itemize all of the online purchases you made and how much sales tax you owe. Since this form is voluntary and results in higher taxes, you can guess how many people actually go through this step. However, like TrisMcC says, most states assess Sales Tax when you register the car in the state. So if you bought a car for $50k in Oregon (no Sales Tax), but then registered it in California (7.5%+ Sales Tax), your registration fees would be the standard fee + $3,750. If you bought your car more than 1 year ago (in California at least), you don't owe any sales tax and if you bought it in a state with lower tax, you just owe the difference. For big online companies, we've started mandating that they collect sales tax on behalf of the customers, so for instance, Amazon now automatically collects sales tax based on where your billing address is. If direct sales were allowed, there'd surely be legislation to ensure that the manufacturers collect the tax for their customers.