Boats built since 1972 are required to have a Hull Identification Number (HIN) permanently attached to the transom on the starboard side above the waterline. This number is a serial number exclusive to your boat and is necessary to title and register it. You should record this number in a safe place. In case of theft it may help identify your boat.
In 1984 a new regulation was passed which requires the HIN number to also be permanently attached in a second unexposed location.