History of the Japanese Koseki (Family Register) System: From the Kōgo Nenjaku to the Present

Japan’s family register, the koseki (戸籍), has existed in some form since 670 and still exists today. It was not continuous, however. As the ancient state weakened in the Heian period, the ancient registers stopped being made, and for about 870 years there was no nationwide register. The next nationwide register was the Jinshin Koseki of 1872. The registers that matter for ancestor research fall into five formats from the Meiji era onward: the Jinshin Koseki, the 1886 format, the 1898 format, the 1915 format, and the 1948 format. This page follows the history in chronological order and explains how each format is used in genealogical research. A section for international researchers is at the end.

Overview

Period	System	Features
670 (Tenji 9)	Kōgo Nenjaku (庚午年籍)	Regarded as Japan’s first nationwide register. Designated for permanent preservation.
690 (Jitō 4)	Kōin Nenjaku (庚寅年籍)	A register based on the household code of the Asuka Kiyomihara Code.
8th century to early 11th century	Registers under the ritsuryō code	Compiled every six years and used as the basis for allotting rice fields. The latest surviving ancient register is from Sanuki Province in 1004.
11th to 16th century	No register	No uniform nationwide register.
17th century to 1871	Shūmon Ninbetsu Aratamechō (宗門人別改帳)	In 1671 the shogunate required the domains to compile them. In effect, a population register.
1872 (Meiji 5)	Jinshin Koseki (壬申戸籍)	The first system to register residents nationwide regardless of status. The registered domicile was the place of residence.
1886 (Meiji 19)	1886-format koseki	A uniform format. The address of the registered domicile changed from a house number to a lot number, and the “removed koseki” system was created.
1898 (Meiji 31)	1898-format koseki	Based on the household (ie). A separate civil status register was kept alongside the koseki.
1915 (Taishō 4)	1915-format koseki	The civil status register was abolished and merged into the koseki.
1948 (Shōwa 23)	1948-format koseki	The head of household was abolished, and the couple became the unit. The basis of the current system.
1994 (Heisei 6) onward	Computerized koseki	Paper registers moved to computer records.
2024 (Reiwa 6)	Wide-area issuance	Koseki certificates can be requested at a municipal office other than the one at the registered domicile.

Ancient registers (7th century to early 11th century)

The Kōgo Nenjaku and the Kōin Nenjaku

The first nationwide register was the Kōgo Nenjaku of 670 (Tenji 9). Ordinary registers were renewed every six years and discarded after 30 years, but the Kōgo Nenjaku was designated for permanent preservation. In 703 it was made the master register and altering it was prohibited. The original has not survived (Wikipedia).

In 690 (Jitō 4) the Kōin Nenjaku was compiled. It was based on the household code of the Asuka Kiyomihara Code, completed in 689. In 692, allotment of rice fields based on the Kōin Nenjaku began in the Kinai region (Wikipedia).

Surviving ancient registers

The oldest surviving registers are those of 702 (Taihō 2) preserved among the Shōsōin documents, covering Mino (Mino no kuni), Chikuzen, Buzen and Bungo provinces. From about this time the practice of compiling a register every six years became established (Wikipedia).

The retention period was 30 years, but because paper was valuable, the backs of discarded registers were reused for other documents. Some ancient registers survive today as documents written on the reverse side of the paper (Wikipedia).

Decline of the system

In the Heian period the ritsuryō system weakened, and it became impossible to maintain a system that covered the whole population. A fragment of a register of Kuga District, Suō Province, dated 908 (Engi 8), survives, but it is thought to be a false register that did not reflect reality, made by provincial governors to reduce their burdens. The latest surviving ancient register is that of Irino Village, Ōuchi District, Sanuki Province, dated 1004 (Kankō 1) (Wikipedia).

Medieval period (11th to 16th century)

There was no uniform nationwide register in the medieval period. Research in this period combines documents kept by individual families and temples and shrines, such as genealogies, family records and temple death registers (kakochō), in place of registers.

Early modern period (late 16th century to 1871)

Religious inquiry and the Shūmon Ninbetsu Aratamechō

The Tokugawa shogunate conducted shūmon aratame (religious inquiry) to enforce the ban on Christianity. In 1665 (Kanbun 5), the shogunate ordered the domains to compile registers of the religious inquiry as well. Separately, after the separation of warriors and farmers, lords had carried out ninbetsu aratame, a census of those liable for labor service, and registers that recorded each person’s religious affiliation in the ninbetsu register came to be made as Shūmon Ninbetsu Aratamechō. In 1671 (Kanbun 11) the shogunate put this on a legal footing and required periodic inquiries (Wikipedia).

These registers recorded, by household, the names and ages of members, together with the name of the temple to which they belonged as parishioners (danna-dera). They were to be compiled every year by the village or town headmen (nanushi, shōya, machidoshiyori), although in some areas they later came to be made only every few years. Where annual volumes survive, changes in a household’s composition can be followed year by year (Wikipedia).

However, in domains such as Hagi, which had their own registration system from an early date, few Shūmon Ninbetsu Aratamechō survive. How much survives differs by domain and region, and there was no nationwide format.

The Jinshin Koseki (1872)

Enactment of the Family Register Law

The Family Register Law was promulgated on the 4th day of the 4th month of Meiji 4 (22 May 1871) as Grand Council of State Proclamation No. 170, and took effect on 1 February 1872 (Meiji 5). The year’s sexagenary designation was Jinshin, hence the name Jinshin Koseki. It was the first register in Japan that covered all residents nationwide under one system, regardless of status (Wikipedia).

Contents

The unit of compilation was the “household” (ko), and the registered domicile was the place of residence. Because status and address were registered together, it also served the function of a residence record. Status categories (zokushō) included the imperial family, kazoku (peerage), shizoku (former samurai), sotsuzoku and commoners (heimin); kazoku and shizoku had their stipends recorded, and commoners had occupations such as farming, crafts and commerce recorded. Entries for the family temple and tutelary shrine continued until they were abolished in 1885 (Meiji 18) (Wikipedia).

The Jinshin Koseki contained criminal records and status entries, and in some regions derogatory terms for outcaste groups were also recorded. Because this led to discrimination, a circular of the director of the Civil Affairs Bureau on 29 March 1968 (Shōwa 43) prohibited inspection. It cannot be inspected by the general public today. In ancestor research, you therefore assume that the Jinshin Koseki cannot be reached directly, and begin with the 1886 format and later (Wikipedia).

Development of the surname system

Surname rules also changed in this period. In 1870 (Meiji 3) commoners were permitted to use surnames, and on 13 February 1875 (Meiji 8) an ordinance made it compulsory for all people to use one. In the following year (1876), a wife was to use her natal family’s name. A system in which spouses share one surname was established in the old Civil Code of 1898 (Meiji 31) (Wikipedia).

The 1886 format (Meiji 19)

On 16 October 1886 (Meiji 19), the “Procedures for Handling Family Registers” (Ministry of Home Affairs Ordinance No. 22) and the “Family Register Entry Forms” (Ministry of Home Affairs Instruction No. 20) were issued, and registers in a uniform format were created. The Jinshin Koseki were gradually replaced with registers in this new format from November of that year (Wikipedia).

In the 1886 format, the address of the registered domicile changed from a house number to a lot number, and the system of “removed koseki” (joseki) was created. The oldest register you can obtain today is, in many cases, one in the 1886 format. From it you can confirm the names and relationships of people born in the last years of the Edo period. In the Family Register Law of 1898 (Meiji 31), registers of this format were treated as “reformed original registers” (kaisei genkoseki) (Wikipedia).

The 1898 format (Meiji 31)

The Family Register Law (Law No. 12) was promulgated on 15 June 1898 and took effect on 16 July of the same year. Under it, the household became the basic unit, and a civil status register was established separately from the family register. Handling was governed by the “Procedures for Handling the Family Register Law” (Ministry of Justice Instruction No. 5 of 13 July of that year) (Wikipedia).

The 1915 format (Taishō 4)

An amendment to the Family Register Law (Law No. 26) was promulgated on 30 March 1914 (Taishō 3) and took effect on 1 January 1915 (Taishō 4). It abolished the complicated civil status register and merged it into the family register. Handling was governed by the “Enforcement Rules of the Family Register Law” (Ministry of Justice Ordinance No. 7 of 3 October 1914) (Wikipedia).

Inner territories and outer territories

Before the war, the content of the registration system differed from region to region. The Law on Common Application (Kyōtsū-hō, Law No. 39, promulgated on 17 April 1918, Taishō 7) set out how registers were to be handled when people belonging to different regions married or were adopted. Registers connected with Korea, Taiwan and similar territories may require inquiries to institutions other than the municipality of the registered domicile (Wikipedia).

The 1948 format (Shōwa 23)

Under the Constitution of Japan, the Civil Code was amended in 1947 (Shōwa 22) and the household system was abolished, and the Family Register Law was also completely revised (Law No. 224 of 22 December). The new law took effect on 1 January 1948 (Shōwa 23). Handling was governed by the “Enforcement Rules of the Family Register Law” (Ministry of Justice Ordinance No. 94 of 29 December) (Wikipedia).

This register abolishes the head of household and is compiled for each couple. The first person listed is called the “hittōsha” (first-named person), and status categories such as kazoku, shizoku and commoner were also abolished. In registers from 1 January 1948 onward, only one married couple and their children who share the couple’s surname can be entered. When a child in the parents’ register marries, a new register is therefore created (Wikipedia).

Reform of the registers (kaisei)

Because of postwar disorder, the work of rewriting registers of the old law into the new format (kaisei) was actually carried out from about 1957 to 1965. The largest reform was carried out under a Ministry of Justice Ordinance (No. 27) of 1957 (Shōwa 32), and the registers before that reform are called “Shōwa kaisei genkoseki”. The current register may not carry over people who were removed before the reform, or some status entries, so you need to trace back through the reformed original registers one by one (Wikipedia).

Computerization and after (1994 onward)

An amendment of the Family Register Law in 1994 (Heisei 6) made it possible to process family register work by computer. Reform under Ministry of Justice Ordinance No. 51 of 1994 was carried out, and computerization proceeded municipality by municipality. Paper registers reformed through computerization are also treated as reformed original registers (Wikipedia).

Registers of removed persons are kept for at least 150 years after removal. The retention period became 150 years under a Ministry of Justice Ordinance (No. 22) of 2010 (Heisei 22). Before that it was 80 years (Wikipedia).

Wide-area issuance and readings of names

On 1 March 2024 (Reiwa 6), the Act Partially Amending the Family Register Act (Law No. 17 of 2019) took effect, and it became possible to request koseki certificates at a municipal office other than the one at the registered domicile (wide-area issuance). Those who can request are limited to the person, the spouse, direct ascendants (parents, grandparents and so on) and direct descendants (children, grandchildren and so on). The request must be made in person at the family register counter of a municipal office; requests by post or through an agent are not accepted (Ministry of Justice of Japan).

What can be requested through wide-area issuance are koseki certificates and removed-koseki certificates. Certificates of partial matters and of individual matters cannot be requested. Some registers and removed registers that have not been computerized are also excluded. Please check at the office where you apply whether items such as reformed original registers are covered (Ministry of Justice of Japan).

On 26 May 2025 (Reiwa 7), the Act Partially Amending the Family Register Act (Law No. 48 of 2023) took effect, and the readings (furigana) of names are now entered in the koseki.

How to use each format in research

Format	Main use	Points to note
Current koseki	Starting point. Trace from yourself to parents and grandparents.	Only one couple and their children are entered. Go further back through removed and reformed original registers.
1948 format	Confirm movements of registers from 1948 onward.	Obtain the reformed original register to confirm what was in the register before reform.
1915 and 1898 formats	Confirm the composition of the household centered on the head.	In the 1898 format a civil status register was kept separately; in 1915 it was merged into the koseki.
1886 format	Reaches people born in the last years of the Edo period.	In many cases the oldest register that can be obtained.
Jinshin Koseki	―	Inspection was prohibited in 1968 and it is not open to the general public.

Besides differences of format, registers have habits of entry that vary by region and period. Do not take the contents of a register at face value; check them against other materials.

Notes for international researchers

Who is entered in a koseki

The koseki is a register of Japanese nationals. A foreign national is not entered as a member of a koseki; a marriage to a foreign spouse is recorded in the Japanese spouse’s register. A person who loses Japanese nationality is removed from the register. If your ancestor emigrated, whether a register exists depends on whether they kept Japanese nationality and whether the family’s register remained at the home municipality.

Registered domicile (honseki)

To request a register you need to know the honseki (本籍), the registered domicile. It is the place where the register is kept, and it does not have to be where the family lived. A family may live in one prefecture for generations while its register remains in another.

Who can request, and how

The persons who can request through wide-area issuance are given above, and it is by counter request only. Researchers living abroad therefore cannot use it. In general you would apply to the municipal office of the registered domicile, in Japanese, or ask a Japan-based professional. Obtaining a register through an agent for ancestor research can raise legal issues in Japan, so ask a qualified professional before doing so. See also Understanding Japanese Family Registers (Koseki).

Era names and calendars

Dates in a koseki are written with Japanese era names.

Era	Year 1 is	Years
Meiji (明治)	1868	1868 to 1912
Taishō (大正)	1912	1912 to 1926
Shōwa (昭和)	1926	1926 to 1989
Heisei (平成)	1989	1989 to 2019
Reiwa (令和)	2019	2019 to present

To convert, add the era year to the year before the era began (for example, Meiji 19 is 1867 + 19 = 1886). Dates before 1873 follow the old lunisolar calendar, so a month and day in Meiji 5 or earlier does not correspond directly to the same month and day in the Gregorian calendar.

Names and characters

Names in a koseki are written with the family name first. Old forms of characters and variant characters are common, and the same characters can be read in more than one way. Readings were not recorded in the koseki until 2025, so do not assume how a name was read from the characters alone.

Depth varies by municipality

How far back you can go depends on whether the municipality still holds the old removed registers. Registers may have been disposed of after the retention period or lost to war and disasters.

Glossary

Term	Meaning
Koseki (戸籍)	Family register
Honseki (本籍)	Registered domicile, the place where the register is kept
Koshu (戸主)	Head of household, the central person in registers before 1948
Hittōsha (筆頭者)	First-named person in a register from 1948
Joseki (除籍)	Removal; a register from which all members have been removed
Kaisei genkoseki (改製原戸籍)	Reformed original register; the register as it stood before a reform
Tōhon (謄本)	Full copy
Shōhon (抄本)	Extract of individual matters
Zokushō (族称)	Status category such as kazoku, shizoku or commoner, recorded until 1948