The two systems, side by side
State registration is administered by your state (usually the DMV, a tax collector, or a wildlife/boating agency). It assigns a registration number displayed on the bow, issues a decal, and — in most states — a state title proving ownership. This is the ordinary path for recreational boats.
Federal documentation is a national registration of a vessel with the U.S. Coast Guard's National Vessel Documentation Center (NVDC). Instead of a bow number, a documented vessel receives an official number carved into the hull's main beam, and it displays its name and hailing port on the exterior. Documentation is a federal record of the vessel's nationality and ownership; it is renewed annually.
Who MUST be documented
Under 46 U.S.C. Chapter 121 and 46 CFR Part 67, a vessel of at least 5 net tons that operates in coastwise trade (carrying merchandise or passengers between U.S. points) or in the fisheries on navigable waters generally must be documented with a coastwise or fishery endorsement. Commercial operators — charter fishing boats, tugs, workboats, and inspected passenger vessels above the threshold — typically fall here.
"Net tons" is a measure of a vessel's enclosed volume, not its weight. Five net tons works out to roughly 25–30 feet for most hull forms, but the only way to know is the vessel's measured tonnage, not its length.
Who MAY be documented (but doesn't have to)
A recreational vessel of at least 5 net tons that is wholly owned by a U.S. citizen is eligible for a recreational endorsement even though it will never carry passengers for hire (46 CFR 67.5). Owners choose documentation for practical reasons: it is recognized internationally when cruising foreign waters, it can simplify financing (marine lenders often require a documented vessel for a Preferred Ship's Mortgage), and it provides a clean federal chain of title.
Documentation here is optional. If your boat is under 5 net tons, or you simply prefer state registration, you are not required to document it.
Who registers with the state
Most recreational motorboats — and, in many states, sailboats and even some non-powered craft above a length threshold — must be registered with the state where they are principally used. The state issues the bow number and decal.
Crucially, documenting a vessel federally does not automatically exempt it from state requirements. Many states still require a federally documented vessel that is kept or used on their waters to be registered (though it is not state-titled, because the USCG documentation is the ownership record). Florida is a clear example — see the Florida boat registration guide for how a documented vessel is registered but not titled there.
Can you have both? Usually yes
The common real-world setup for a larger recreational boat is: a federal Certificate of Documentation (the ownership/nationality record) plus a state registration decal (because the state requires it for a vessel used on its waters). What you do not get in that case is a state title — the federal COD replaces it.
A documented vessel must not display a state registration number on the bow; it shows its name and hailing port instead. If your state requires registration of a documented vessel, follow the state's specific process for documented vessels (usually a registration without a title, using a copy of the COD as proof of ownership).
The numbers on your boat: HIN vs official number vs registration number
These three identifiers are easy to confuse:
The Hull Identification Number (HIN) is a 12-character code the manufacturer permanently affixes to the hull, required on every boat built since November 1, 1972 under 33 CFR Part 181. It identifies the builder and the hull — like a VIN on a car — and never changes. Decode yours with the HIN decoder.
The state registration number (the bow number, e.g. "FL 1234 AB") is assigned by the state and displayed on both sides of the bow. It belongs to the registration, not the hull, and changes if the boat moves states.
The USCG official number is assigned by the NVDC to a documented vessel, marked internally on the hull, and preceded by "NO." A documented vessel has an official number instead of a bow number.
Practical decision guidance
Work through it in order:
1. Is the boat under 5 net tons (roughly under ~25 ft)? Then documentation isn't an option — register with your state.
2. Will it operate commercially in coastwise trade or the fisheries at 5+ net tons? Then it generally must be documented, with the matching endorsement.
3. Is it a 5+ net-ton recreational boat owned by a U.S. citizen? Documentation is optional — worth it if you cruise internationally or need marine financing; otherwise state registration alone is simpler and cheaper.
4. Whatever you choose, check whether your state still requires registration of a documented vessel, and verify the HIN before you buy using the boat-buying checklist.