There was an earlier thread on this. All states that have a sales tax also have a use tax at the same rate. Sales tax covers items purchsed in-state and use tax coovers items bought outside the stte and brought in. There are three relevant situations: (1) you buy the boat
and keep it in the same state, you will pay sales tax in that state when you reregister the boat
in your name; (2) You buy the boat and move it to another state, you will pay use tax in that state but receive a credot for any tax paid in the selling state. Note that there will be time limit within which the boat has to moved or be subject to sales tax in the selling state. (3) You buy the boat and move to a non-sales tax state, you pay no sales or use tax.
, in every state in which I am familiar, physical presence of the boat is the determining factor. Again, every state of which I am aware requires registration
in that state once the boat is in state waters for a specified period of time (the time varies from state to state). Note also that being subject to a state's registration requirements can open other issues such as personal property tax, excise tax and the like depending on the state.
Simply registering the boat in DE will not suffice if the boat is not truly docked in Delaware. Most coastal states, especially CA and FLA, have fairly vigorous enforcement as you are talking about sales tax on a lot of very expensive toys. Fla actually had, and as far as I know still has, a reporting requirement for marinas
to make spotting violators easier.
When I practiced tax law, I represented more than a few NE owners caught spending more time than allowed in Fla waters and they were hit uup with very substantial tax bills.