“Cognomen” data-wafer is the official Administratum designation in the Imperium for a citizen’s identity card. In a hive, it is one of the only viable means of tracking, taxing and identifying the citizenry. Cognomen are usually blank iron-grey, punched-metal squares (about the size and shape of a Imperial tarot card) and designed to be read by data-slates and cogitator systems. The only feature on the face of a Cognomen is the symbol of the issuing habitat, guild or Adepta whom the citizen serves. In some ways, ownership of a cognomen is frighteningly important: it represents the only legal proof of identity, a right to work and even to be fed and housed for the average citizen. Its loss might genuinely mean starvation, abandonment, arrest or even being cast down into the fringes in the blind face of Imperial bureaucracy. There is, of course, a thriving trade in the theft and falsification of cognomen, the price for a “face” varies on the identity fabricated or stolen, and can range from a few gelts to thousands.
All children born in the worlds under Imperial rule get their Cognomen only after admitting gene-print and negative psychic screening results at the age of 10. Age which is considered mature enough for military conscription.
In feudal Imperial societies only upper caste of the planet have a cognomen. In those planets a majority of population is classified as serfs, who do not have privileges of an Imperial citizen.