Koseki

A koseki (Japanese: 戸籍) or family register is Japan's official system for recording and certifying Japanese nationality and family relationships. It records births, parentage, adoptions, marriages, divorces and deaths, and is maintained by the municipality of the registered domicile (honseki). The modern nationwide system dates from 1872 and organizes civil-status information around family registers rather than primarily around individuals.

Japanese nationals are entered in a koseki, and changes in civil status are reported to municipal authorities and recorded in it. Marriage, consensual divorce, acknowledgement of paternity, and adoption generally take legal effect through notification, while births and deaths must be reported after they occur. By linking successive registers and associated records, the system provides long-term legal continuity and allows family relationships, changes in civil status, and residence history to be traced across generations and, in principle, for well over a century.

Koseki registration is distinct from resident registration. Japanese nationals and foreign residents register their actual residence through the jūminhyō (住民票) system. Foreign nationals cannot be members of a koseki, although they may be recorded in one as, for example, the spouse or parent of a Japanese national. Members of the Imperial Family are recorded separately in the Register of Imperial Lineage.