Hull identification number: what the owner must do

Registration & documentation · Power & sail

The hull identification number (HIN) links your registration to the hull. Federal rules forbid anyone to remove or alter it without Coast Guard authorization, and your state must confirm the boat has a valid HIN before issuing, renewing or transferring a registration (33 CFR 181.35, 174.16).

Keep it intact

• No one may remove or alter a hull identification number unless the Commandant of the Coast Guard authorizes it (33 CFR 181.35).
• Boats carry two identical HINs: a primary one on the outside of the hull, usually on the starboard side of the transom near the top, and a duplicate in a hidden spot inside (33 CFR 181.29).
• Don't paint over, cover, deface or obscure either number. When you repaint, re-gelcoat or repair the transom, plan the work so the HIN stays visible and unaltered (BoatUS Foundation; WA Department of Licensing).
• Operating a boat in violation of the federal boat-safety rules, which include the HIN rules, is itself prohibited (46 U.S.C. 4307(b)).

Registration and the HIN

• The HIN appears on your state certificate of number (33 CFR 174.19(a)(7)).
• Before it issues, renews or updates the ownership on a certificate of number, the state must check that the boat has a valid primary HIN (33 CFR 174.16(b)).
• If the state finds no valid HIN, it assigns one and checks that you have permanently fixed it to the boat before it acts on your registration (33 CFR 174.16(c)).
• If you built or imported a boat for your own use, get a HIN from your state's issuing authority and fix it to the boat permanently (33 CFR 181.23(b)).

If the number is damaged or missing

• Ask your state boating agency before you do anything about a damaged or unreadable HIN, because changes need authorization (33 CFR 181.35).
• Washington's guidance, for example, says to leave the original HIN in place and fix a newly assigned HIN above, below or next to it. Follow your own state's instructions (WA Department of Licensing).

The rules: 33 CFR 181.23 · 33 CFR 181.29 · 33 CFR 181.35 · 33 CFR 174.16 · 33 CFR 174.19 · 46 U.S.C. 4307

A plain-language summary of federal rules for recreational boats, checked against the rules’ own text and a second source, and written in our own words. It isn’t legal advice. States add rules of their own, and rules change — the links above go to the current official text.