The Danish bicycle VIN-system is a system introduced in 1942 by the Danish government, providing all bicycles in Denmark with a unique code. The VIN code is a combination of letters and digits embedded into the bicycle frame and consists of a manufacturer code, a serial number, and construction year code.

Since 1948, it has been illegal^[1] to sell bicycle frames in Denmark without an embedded VIN. Because of this, insurance companies in Denmark will not pay indemnities for stolen bicycles without a VIN.^[2]

By default, the VIN is to be engraved into the seat tube or the down tube, but if these are made of such a material that hinders this, it may alternately be put on the bottom bracket shell. In very special instances, and only with the approval of the Danish National Police Commissioner’s Office, it may be applied by other means and on other locations.^[1]

The bicycle VIN is constructed of three elements: a letter-block, a digit-block and a letter-block:

The manufacturers-code, is a 1, 2, 3 or 4-letter block. If the code starts with a W, it is an imported bicycle frame. The second block is the frame serial number from that manufacturer. This shall have at least one digit, but can otherwise have any number of digits. The third block is a single letter code that identifies the production year. Certain limits regarding letters are instated for the VIN:^[3]

• I is omitted as it can be confused with 1 (one)
• O is omitted as it can be confused with 0 (zero)
• Y is omitted as it can be confused with V
• W is omitted, to avoid confusion with the manufacturer code (where W is reserved for imported frames)

In the examples above, the first bicycle is a bicycle imported by FDB, with serial number 1234 and made in either 1963, 1984 or 2005. The second bike is an SCO bicycle, with serial number 57, made in 1942, 1964, 1985 or 2006.

• Bicycle locker
• Bicycle theft
• List of bicycle registers
• Outline of cycling