The identity number or passport (serial) number is a string that identifies an entrant and the passport issued to them. Unlike what the name suggests, it is a 10-character-long string consisting of both numbers and letters with a dash in the middle (e.g. T6H73-BP2J4). An exception to this is Jorji Costava's passport, which contains only 9 characters (GCD7-FMBAR). The string must be consistent on each document they are carrying. If the string is not consistent on all documents, the entrant can be detained.
Notably, it is not present on the Arstotzkan ID card.