"North Dakota passed a law in 1987 requiring out-of-state mail-order houses to collect and pay a use tax on goods purchased for use in the state. Quill Corporation refused to comply and the state of North Dakota took them to state court. The trial court ruled in Quill's favor and found that based on Supreme Court precedent in a 1969 case (National Bellas Hess, Inc. v. Department of Revenue of Ill.) the law created an unconstitutional burden on interstate commerce based on the Fourteenth Amendment's due process clause. In addition the Supreme Court found it conflicted with the commerce clause because, “The very purpose of the Commerce Clause was to ensure a national economy free from such unjustifiable local entanglements. Under the Constitution, this is a domain where Congress alone has the power of regulation and control.”
Read more: The Supreme Court: Sales Taxes on Mail Orders — Infoplease.com
http://www.infoplease.com/cig/supreme-court/sales-taxes-mail-orders.html#ixzz2B2rrGLe0"
The upshot is that you typically have to charge and declare/pay sales tax if your customer resides in the same state you're doing business in. You don't have to charge out of state customers sales tax.
The law varies from state to state however and NY has tried to find a way around the Constitution by requiring any business w/ a physical presence in NYS to charge sales tax on customers from NYS. Predictably many online retailers have simply chosen to move out of state leaving NYS w/ no tax revenue (and less jobs) from those businesses. Stupid.
Machiavelli, a man so ruthless his name/nickname serves as euphemisms for Satan, advised the Prince not to tax trade routes. Not because he was a nice guy obviously, but because the net effect is that you wind up losing money in the long run. NYS, more ruthless than Machiavelli and not nearly as smart.
Obviously, your revenue will still be taxed at around 40% when all is said and done. Hope this helps somewhat, keep in mind I'm neither a lawyer nor an accountant, ymmv.