What I understand is that sales taxes arise where the ownership of the merchandise changes hands occurs. Most products sold online are shipped FOB (Free on Board) Shipping Point meaning that the buyers ownership takes place at the sellers shipping dock. The alternative to that is FOB Destination in which case the seller retains ownership until delivered to the buyer’s dock.
The state in which the ownership transfer takes place is the place where any sales tax can be assessed (usually FOB Shipping Point these days). It only makes sense. Imagine the paperwork SNAFU if a seller ships FOB Destination! He’d have to keep track of taxes for all fifty states (57?), collect them, and then remit them to the buyer’s state (quarterly???) What a nightmare!
Actually, it is currently charged FOB destination.
When I buy off Amazon, I pay KY sales tax. But they have a KY presence. I suppose with this new law, that would still apply, but for those that don’t have a KY address, if they have to pay their state’s sales tax, I suspect a lot of them would move to states like Oregon, which have no sales tax.
I suspect, because the SD law was FOB destination, this applies to FOB destination.
And it’s not just fifty states if ALL sales taxes apply. Cities, and counties charge a part of the sales tax, and there are even tax surcharges for some rally successful “tax districts” which could include a single shopping mall or strip mall.
Governments get pretty creative in getting their protection money.