The ninth to eleventh digit of the UIC wagon number is the consecutive numbering of wagons of the same type.

Within the individual wagon types, one or more number groups are assigned for each type of freight wagon defined by identical technical characteristics. For a long time, freight wagons were characterized by comparatively few types with many examples. For this reason, the eighth digit was also used for the serial number. As a rule, this was recognizable by the address without spaces.