A question I didn't see answered:
Where is home? Huge difference if the boat is coming from the
USA vs the UK. Sales tax paid in the
USA makes no difference and if you are a UK resident, there is no temporary
import option.
Nodge: Best to check with the authorities (maybe anonymously). This smacks of the idea of putting a fake value on a boat/car so when you register it, you get a lower tax bill and if they catch you most authorities aren't happy about it. Now if you buy a $50k boat and put down $30k on the bill of
sale, good chance you get away with it as they really don't know what the value is but $1 and it's pretty obvious there is more to the story. My guess is they will assume that the yard bills were actually part of the sales
price since it was a requirement of the deal that you pay the yard bills before you could take full possession of the boat. Worst case they could assign a value of there choosing and let you either pay or provide proof to the contrary.