It serves to find out the original personal identification in case the person received NID (alternative identification number) in case of duplicity. This identification is not unique. It contains:
- the birth number (9-digits birth number is padded on the right with a space) for Czech individuals,
- IC (organization identification number) for Czech legal entities,
- the birth date in format yyyymmdd for foreign individuals,
- the foreign identification number for foreign legal entities.