Koseki

A koseki (戸籍) or family register is a Japanese family registry. Japanese law requires all Japanese households to make notifications of their vital records (such as births, adoptions, deaths, marriages and divorces) to their local municipal authority. Domestic aspects such as marriages, divorces, acknowledgements of paternity of non-marital children, and adoptions, are only legitimized if they are recorded on the koseki. Births and deaths become legally effective as they happen, but such events must be filed by family members or other persons as allowed by law.

Koseki registration is required by all Japanese citizens, and possessing one is definitive proof of Japanese nationality, unless a renunciation application is made, which is subsequently recorded on the koseki for reference. Along with the koseki registration, Japanese citizens are individually required to submit a notice of residence (Jūminhyō, 住民票). Foreign residents are not allowed to file for a koseki, and are only required to submit a Jūminhyō.