Every factory built bike will have a serial number, to identify the make, model and date of production. The serial number can be in different places depending on the manufacturer.
Most typically, the serial number is printed or engraved on the underside of the Bottom Bracket Shell - under the cranks. Other common places include the outer face of the non-drive side chainstay, or under the head badge. If you are having trouble, reference the manufacturer's website for helpful tips.
Take a lot of pictures.
Not just for the 'gram. Pictures of you with the bike will prove ownership. Pictures of the bicycles drive-side will allow experts to identify unique components.
Plan on taking these pictures:
Serial number You and the Bike together Drive-side picture of the bike to display components Overhead cockpit shot Any unique or non-stock additions
Formerly NationalBikeRegistry.com, Project529.com is a free online database which will hold your serial numbers for all of your bikes.
After creating an account, input all the previous data into these web forms.
Congratulations! Your serial number is now saved!