system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do we pay sales tax on used (pre-owned) vehicles? Hasn't the tax been paid already on it once (when it was new)?

Is there such a thing as a double taxing rule? 

I know when normal items are purchased regularly, the business are tax-exempt and the sales tax is then passed and paid by the consumer. Why can a car be taxed and retaxed every time it is sold?
gpt
Sales tax is a tax on the transaction, not the item.  There's other sorts of taxes, such as a VAT (value added tax) that specifically target goods.

The item being secondhand makes no difference to sales tax.