With so many states strapped for cash, state legislatures are looking at every revenue-raising opportunity. Applying tax to Internet sales is one area. Four states have statutes on the books now (New York, North Carolina, Rhode Island, and now Colorado), and many more states are considering the possibility.
Internet merchants have been shielded from sales tax by a 1992 Supreme Court decision that said mail order companies did not have to charge sales tax if they had no physical facilities in the state where the customer lives.
The Colorado law follows the Supreme Court decision. The law states, "A website that sells tangible personal property collects tax in the same manner as a mail order business that sends catalogs to customers to place phone or mail orders. If the seller and the customer are both located in the same taxing jurisdiction, then the seller must collect that tax."
Merchants used to have a link to Amazon on their web sites. Purchases made through these links would generate income for the referring merchants, who are called affiliates. Amazon didn't want to start collecting sales tax for Colorado, so it cut off relations with its affiliate businesses in the state.
If the internet merchant does not collect a sales tax, most states have laws that require the customer to pay the sales tax to the state directly. It's called a use tax rather than sales tax.
Here's what Colorado says about the purchaser being required to pay the tax: "If you are buying from a vendor not located in Colorado, you will probably not pay sales tax to the seller, but will pay state and possibly a special district use tax directly to the state of Colorado on form DR0252, 'Consumer Use Tax Return,' found at www.taxcolorado.com."
In practice, hardly anyone pays attention to the use tax laws. Without information from the merchants, the states have no way of knowing who bought what. So the states are missing out on revenues from purchases of goods made online from companies that are over the state line.
My guess is that there will be some change in law at the federal level that will require mail order and internet merchants to collect sales tax for the states. Internet merchants are already required to collect tax on sales in the state where they have a physical presence (Washington state for Amazon, for example) so it can't be that hard for the companies to start collecting tax on sales to any state.