The Basic Guide to Boat Numbering

As a person who is keen on boat ownership, we are sure that you will have noticed the numbers on the sides of boats and wondered exactly what they mean. Boat numbering is one of the primary and essential aspects of vessel ownership, and it is really important to understand the guidelines that can help you as a boat owner fall in compliance with all of the rules and regulations. It will help you to avoid any potential legal issues in the future. With this in mind, here are some of the basics of boat numbering that are worth keeping in mind.


The HIN, of Hull Identification Number, is the official number that you will see on the side of any documented vessel. Every single boat that has been manufactured after 1972 will have been assigned its own unique HIN, and this serves as the boat’s unique identifier that needs to be displayed on its transom or starboard outboard side, above the waterline. The HIN is a 12-character alphanumeric code that can provide information on the manufacturer, serial number, and more.

State Registration Number

If your boat is in a category that requires state registration, it will also need to display a state-specific number along with its HIN. This is a number that is assigned by the boating authority of the state or the Department of Motor Vehicles. These numbers need to be displayed on both sides of the bow of the vessel, in a contrasting color to ensure visibility, and this visibility is mainly for authorities if they should ever need to identify your vessel when out on the water when you are in trouble or need to be contacted for any reason.

Boat Numbering

How To Put Numbers On A Vessel

On a documented vessel, the official number needs to be preceded by ‘NO’. This should be marked at least three inches in height in block-type Arabic numerals and placed on a clearly visible interior structural part of the boat’s hull. Owners are trusted to use their own common sense when determining what and what isn’t ‘clearly visible’. 

You need to permanently affix this number in such a fashion that removing or altering it would look extremely obvious, in the form of damage to the area. This will come in handy should you ever find yourself in the position of your vessel being stolen, as the thieves will have to cause marked damage in order to try to hide your original serial numbers.

If you should ever find yourself in need of some assistance when completing and submitting the various examples of boat documentation, including those that confirm your boat numbering, don’t hesitate to take advantage of the services offered on the US Vessel Registrar website. Feel free to get in touch with one of our experienced team members and they will be more than happy to provide the answers to any questions that you might have. We very much look forward to being able to help you with anything within our remit.