In New York State, it is the law that all undeclared purchases and uses for which sales tax would have been charged, including out of state purchases brought back or shipped to a New York address, are in fact subject to "use tax". You are required to either declare, on your income tax form (Line 56 last year), the amount of purchases and remit the appropriate sales tax along with your annual income tax or add a fixed amount based on your declared gross income. In other words, the state of NY assumes that you've been buying (just to keep on topic) coins from out of state dealers and you owe the tax. It's worse... in NY State and county both charge sales tax. So... if I buy coins from an out of county dealer that charges less sales tax than that what is charged in my county, I am supposed to send New York the difference. I am only describing the law as I understand it here... not rendering any opinion as to how many people abide by it...
George: very accuate and I especially enjoyed hte last sentence. In adidtion, if you fill out customs forms for purchases made outside the country NYS sends you a bill for the sales tax that is due on the purchases. ( I actually saw this one time.)