Both national retailers and Amazon probably have the capabilities to do this, but equal protection clause states that you can't single out a single entity with a law. Would you have computing this be a barrier to entry for anyone who wants to sell over the internet? Especially as services and digital goods might also be considered taxable under certain jurisdictions.
I see your point that this could be a problem, but it's also a problem that brick-and-mortar shops have to pay tax while Amazon doesn't, no? Equal protection (or competitiveness) goes both ways.
Neither have to pay the tax, it's just a question of who the state can compel to collect the tax on behalf of customers. The real tax evaders here are the customers, who are required to pay a use tax for out of state purchases. Of course, clamping down on this is political suicide so it doesn't happen.
I think the classical argument as to why the brick and mortars have to collect is because they actually see a benefit from the local government in the form of police, fire protection and transportation in a way that Amazon does not (at least not directly).
The real tax evaders here are the customers, who are required to pay a use tax for out of state purchases. Of course, clamping down on this is political suicide so it doesn't happen.
Actually North Carolina tried to do exactly that. They did a tax audit of Amazon, and tried to get Amazon to turn over records as a part of that which would let them go after state residents for owed sales tax. The case went to court and was settled last February in Amazon's favor. Amazon wound up giving North Carolina detailed records of every item shipped to a North Carolina address, but with all personal identifying information stripped so that North Carolina could not figure out who had purchased what.
