A koseki (戸籍) is a family registry. Japanese law requires all households (ie) to report births, deaths, marriages, divorces, and criminal convictions to their local authority, which compiles the information into a detailed family tree that encompasses everyone within their jurisdiction. If such events are not recorded in the koseki, they are not officially acknowledged by the Japanese government.

While similar systems have been employed in Japan since ancient times, the modern koseki, encompassing all of Japan's citizenry, appeared in the late 1800's, immediately following the Meiji Restoration. This was the first time in history that all Japanese people were required to have family names as well as given names. Records were originally kept in lengthy paper volumes, but were translated to digital format in 2002 and are now kept entirely by computer.

The koseki fills the role that birth certificates, death certificates, marriage licenses, and the census play in other countries, all in one package. It is also based on family rather than each individual. Because they often contain sensitive information, such as adoption records, they are usually held in strict privacy by the government, and are usually only shown to family members or the police. But anyone who is listed on a koseki, even if their name has been crossed off by reason of divorce and even if they are not a Japanese citizen, is legally able to get a copy of that koseki. They can get one in person in Japan, or by mail outside of Japan. Lawyers can also get copies of any koseki if a person listed is involved in legal proceedings.

A typical koseki has one page for the household's parents and their first two children: additional children are recorded on additional pages. Any changes to this information have to be sealed by an official registrar.

Note that the koseki system is different from the jyuuminhyou, or Residency Registration system, with which is it sometimes confused.

External links

• Modern koseki
• Taisho-era koseki
• Practical information on obtaining and using a koseki for Family Law related purposes in Japan
• Information on Japan's Jûminhyô, or Residency Registration system