The family register, known as Koseki () in Japan, is a system of documents in which all members of nation states or communities register by family units. This is a uniquely East Asian system and can be found at different times in China, Japan and Korea. Koseki started in Japan in the seventh century to keep all family records of birth, death, marriage and expatriation in order to impose a tax, military service and other civic services. The family register system is still active in Japan as a central state apparatus for maintaining patriarchal society based on family genealogies.