The UIC wagon number (formerly wagon number) enables freight and passenger wagons to be uniquely identified and contains important key data for rail traffic.
The wagon number is specified by the UIC and forms a common language between railroad companies, infrastructure managers and the responsible state authorities. Initially, the computerized numbers were only mandatory for standard and broad-gauge vehicles that were to be used internationally. For narrow-gauge vehicles, the use of the system was and is voluntary. Since the mandatory introduction of the UIC numbers in 2006, they are no longer changed when vehicles are sold to other countries in the area of application. Only the keeper code after the vehicle number is adjusted.
A complete wagon number consists of twelve digits, the individual digits of the wagon number have the following meaning:
| first and second digit: | Type of vehicle and indication of the interoperability capacity (on multiple units, type) |
| third and fourth digit: | UIC country code (owner before 2006) |
| fifth to eighth digit: | Vehicle type |
| ninth to eleventh digit: | Individual running number (serial number) |
| twelfth digit: | Check digit |