Hull identification number (HIN): what it is and where to find it
The HIN is a 12-character number stamped or molded into every boat hull built in the United States since 1972. It identifies the specific hull the way a VIN identifies a vehicle.
Where to find it
Look at the right (starboard) side of the transom — the flat back wall of the boat — at or near the top. It is usually molded in, stamped in, or on a plate attached there. If you cannot find it on the transom, check the manufacturer’s paperwork or a second hidden location sometimes present inside the hull.
What it looks like
12 characters, for example: ABC12345D202. The format is:
- First 3 characters: manufacturer code (assigned by the U.S. Coast Guard)
- Next 5 characters: serial number assigned by the manufacturer
- Next 2 characters: model year code
- Last 2 characters: production year
The exact encoding can vary by age of the boat. What matters for a bill of sale is copying the full 12-character string exactly as it appears.
Why it goes on the bill of sale
State agencies use the HIN to check that the boat being titled or registered matches what the seller owned. Without it, the buyer may not be able to complete titling or registration. Florida, for example, requires a bill of sale that includes the hull identification number and length when a used boat comes from a state that does not title boats (FLHSMV vessel titling page, last checked 2026-10-14).
What if the HIN is missing or illegible?
A missing or altered HIN can make it difficult to title the boat. Contact your state agency before completing the sale. Some states have a process for assigning a new HIN to older boats that predate the requirement.