Sales tax/use tax is very complicated and variable by the state in which the boat is purchased and the state in which the boat is registered. Between the 50 states, the variations are almost infinite. Generaly, sales tax is due in the purchase state. Some states (e.g. MD) will waive sales tax if you agree to remove the boat from the state within (I think) 30 days. When you go to register the boat (if required), that state will levy a use tax. Any previously paid sales tax is credited against the use tax. I guess you can "beat the system" if you were to purchase a Hobie in a no sales tax state (DE) and use it in a no registration state (VA, for sail-only boats under 22 LOA). If you want the nitty-gritty in your state, you could ask a keel boat or power boat dealer as they deal with this crap all the time.