A Hull Identification Number — HIN for short — is the unique permanent serial number stamped on every recreational boat built since 1972. Think of it as the VIN of the boat world: a single string of 12 to 14 letters and digits that tells you who built the boat, when it was made, and which exact hull you're looking at.
Whether you're buying a used boat, filing an insurance claim, registering your vessel, or just curious what those numbers on your transom mean, understanding HINs is essential. This guide walks you through everything: the history, the format, how to decode each character, and what to do if your HIN looks wrong.
The HIN at a glance
- Length: 12 characters (US HINs since 1984) or 14 characters (European CE HINs since 1998)
- Characters used: A–Z and 0–9 only, no special characters, no spaces, no dashes (despite how some sources write them)
- Forbidden letters: I, O, Q (look too much like 1, 0)
- Location: Stamped or engraved on the outside of the transom, plus a hidden duplicate inside the boat
- Mandatory since: 1972 in the US, 1998 in the EU
- Cannot be changed without a formal procedure through the issuing authority (USCG, national EU authority, or competent body)
Why HINs exist
Before 1972, US boats had no standardized identification. If a boat was stolen, sank, or was involved in an accident, there was often no way to identify it. Manufacturers used their own numbering systems — some boats had no number at all, others had multiple inconsistent ones.
The 1971 Federal Boat Safety Act changed that. Starting 1 November 1972, the US Coast Guard required every recreational boat built or imported into the United States to carry a unique 12-character Hull Identification Number, permanently affixed to the hull. The format went through one revision in 1984 (the modern "MIC-Serial-Month-Year-ModelYear" format we use today), and has remained stable since.
Europe followed much later. The 1994 Recreational Craft Directive (94/25/EC), replaced in 2013 by directive 2013/53/EU, imposed a similar requirement for all boats sold in the European Economic Area: a 14-character CE HIN following ISO standard 10087. The extra two characters at the front encode the country of origin, reflecting Europe's multi-national nature.
The US HIN format (12 characters)
A US Coast Guard HIN looks like this:
SEA12345K405 └─┬┘└──┬─┘│ │ └┬┘ │ │ │ │ └─ Model year: 05 = 2005 │ │ │ └──── Production year: 4 = 2014 (last digit) │ │ └────── Production month: K = November │ └────────── Hull serial number: 12345 └────────────── MIC: SEA = "Sea Ray"
Position 1–3: The MIC (Manufacturer Identifier Code)
Three letters identifying the manufacturer. There are about 16,000 MICs in the USCG database. Some examples:
- SER — Sea Ray Boats (Knoxville, TN)
- BAY — Bayliner Marine
- BWX — Boston Whaler
- YAM — Yamaha Motor (US)
- 4WN — Four Winns
You can browse the full directory of 4,500+ active MICs on this site, or decode any HIN to see the manufacturer name.
Position 4–8: The hull serial number
Five characters chosen by the manufacturer. Most use sequential numbers (12345, 12346, 12347…) but some incorporate model codes. The serial uniquely identifies the hull within a manufacturer's production. Two different builders can both have hull number 12345 — what makes the HIN globally unique is the combination of MIC + serial.
Position 9: Production month
A single letter encoding the month the boat was actually built:
- A = January, B = February, C = March, D = April
- E = May, F = June, G = July, H = August
- J = September, K = October, L = November, M = December
- The letter I is skipped because it looks too much like the digit 1.
Position 10: Production year (last digit)
A single digit, the last digit of the production year. So a "4" could mean 1984, 1994, 2004, 2014 or 2024 — it's the surrounding context (the model year in positions 11-12, the typical lifespan of that manufacturer) that disambiguates.
Position 11–12: Model year
Two digits encoding the boat's model-year designation. A boat built in late 2014 (production year "4") is often sold as a 2015 model (model year "15"), so production year and model year can differ.
The European CE HIN format (14 characters)
European CE HINs add a 2-letter country code at the front, but otherwise follow the same logic:
DEBAV12345D414 └┬┘└┬┘└──┬─┘│ │ └┬┘ │ │ │ │ │ └─ Model year: 14 = 2014 │ │ │ │ └──── Production year: 4 = 2014 │ │ │ └────── Production month: D = April │ │ └────────── Hull serial number: 12345 │ └────────────── MIC: BAV = Bavaria Yachtbau GmbH └───────────────── Country code: DE = Germany
The country code uses ISO 3166-1 alpha-2 (DE, FR, IT, GB, NL, etc.) and identifies the country that issued the MIC, not necessarily where the boat was built. A boat with a French Bénéteau MIC built in their Polish or US factory still gets a French CE HIN.
Where the HIN must appear
Both US and EU regulations require the HIN to be displayed in two locations:
- Primary HIN — exterior, transom, upper starboard corner. Visible from outside the boat without lifting anything. Stamped or engraved at least 6 mm tall, contrasting with the hull color.
- Secondary HIN — hidden inside the hull. Stamped somewhere a thief is unlikely to find but a surveyor can: behind a deck plate, under a fitting, inside an engine compartment, beneath a cushion. The exact location is up to the builder but must be documented to the authorities.
Both numbers must match exactly. If they don't, that's a major red flag indicating the boat may have been re-titled, salvaged, or stolen. See our used-boat HIN red flags guide for what to look for when buying.
Legal status of the HIN
It is a federal crime in the United States (18 USC § 511) to remove, alter, deface, or knowingly possess a vessel with an altered HIN. Penalties include up to 5 years in prison and forfeiture of the vessel. In the EU, equivalent provisions exist in each member state's national legislation implementing the Recreational Craft Directive.
If your HIN is genuinely damaged or unreadable (sun damage, hull repair, faded paint), you must apply through the proper channel — USCG District Office in the US, or the relevant maritime authority in the EU — to have a new HIN issued. Never restamp or repaint a HIN yourself.
Decoding a HIN: try it now
This site provides a free instant decoder that handles both US and CE formats, with a database of 16,000+ manufacturer codes. Paste any HIN and you'll see manufacturer name, location, production date, model year, and an analysis of any formatting issues.
Frequently asked questions
Is a HIN the same as a VIN?
The HIN is the boat-world equivalent of a car's VIN: a unique permanent identifier required by law on every vessel sold or registered. But the format is different — US HINs are 12 characters, European CE HINs are 14, and the date encoding follows its own rules. A VIN is 17 characters with a checksum digit; a HIN has no checksum.
Where is the HIN located on my boat?
By US federal regulation (33 CFR § 181) and EU directive 2013/53/EU, every recreational boat must display the HIN in two places: a primary HIN on the outboard side of the transom, upper starboard corner, where it's visible from outside the boat; and a duplicate HIN hidden somewhere inside the hull (under a fitting, beneath a deck plate, inside a locker). See our finding-the-HIN guide.
What does each character of a HIN mean?
For US HINs (12 chars): positions 1-3 = MIC (Manufacturer Identifier Code), 4-8 = hull serial number, 9 = production month (A-L excluding I), 10 = last digit of production year, 11-12 = model year. For EU CE HINs (14 chars): positions 1-2 = country code, 3-5 = MIC, 6-10 = serial, 11 = month, 12 = year, 13-14 = model year.
When did HINs become mandatory?
The US Coast Guard required HINs from 1 November 1972 onwards (Federal Boat Safety Act). The EU mandated CE-format HINs from 16 June 1998 under the Recreational Craft Directive. Boats older than these dates often have no HIN or use manufacturer-specific schemes that don't match either modern standard.
Try the decoder
Paste any HIN below and we'll decode it instantly:
Related guides
- Finding the HIN on your boatWhere the Hull Identification Number is hidden on every type of recreational vessel
- HIN format by countryWhy a German HIN looks different from a US one, and how to read each
- Used boat HIN red flagsHow professional surveyors use the HIN to spot stolen, salvaged or fraud-titled boats
- Decode boat year from HINProduction year vs model year, the 1-digit ambiguity, and how to tell a 1984 from a 2014