[repiret]

In the United States, the vendor always pays the sales tax. Its customary for the vendor to itemize it separately on their customer's bill and exclude it from listed prices, but its the vendor who has to write a check to the government, the vendor who has reporting obligations to the tax authorities, and the vendor who gets in trouble if it isn't paid. I suspect its the same in France, but I don't really know.

[bambax]

The vendor collects the sales tax from the customer, and then (a month later) reports it to the government and pays the government back; but the only sales taxes that a vendor owes are the ones it has collected (or, in case of a dispute with the govt, the ones it is assumed to have collected).

If for example a customer buys but does not pay, then the sales tax associated with that purchase is not owed.