In Canada, builders of home built boats are required to obtain an HIN number from the Coast Guard. Simple form and only $5.00 Can. I have been questioned and had to use photos of me building them to prove I did not purchase them in
the USA. When customers build in my shop, I give them an ownership card in which they can put their HIN number and use this card as a transfer of ownership should they sell it. In a recent article published in Wavelength Magazine, the police won't even bother helping with your stolen boat without an HIN number on home builts.

Any sort of number, decal, SIN#, etc. in the boat by the builder usually suffices but Customs officers on both sides can be either friendly or difficult on any given day. Also the transport of stolen boats is quite common across borders as they are much easier to sell far from home.