My Number, Koseki, and Juminhyo Linkages

My Number koseki juminhyo linkage is the system that lets one number connect procedures across Japan's separate civil registers. It saves a second trip to the counter when it applies, and it misleads when a reader assumes the registers have merged into one record.¹

Confirm current details with official sources

Procedures, fees, and requirements can change. Confirm current details at the Digital Agency site.

Overview

My Number is the 12-digit number assigned to every resident who holds a juminhyo, and it is used in social security, tax, and disaster-countermeasure procedures defined by statute or ordinance.¹ Information linkage lets administrative bodies exchange procedure-necessary data over a dedicated network, which reduces the attached documents a resident must submit.¹

The koseki and the juminhyo remain separate registers run by different authorities. My Number connects procedures across them without merging them into a single database.¹²³

What Each System Records

Each register answers a different question. The koseki answers who a Japanese national's family members are.

The juminhyo answers where a resident lives. My Number answers which person an agency record belongs to.

Term	Reading	Meaning
戸籍 (koseki, "family register")	koseki	Family register for Japanese nationals3
住民票 (jūminhyō, "residence record")	jūminhyō	Individual residence record within the municipal register2
個人番号 (kojin bangō, "Individual Number")	kojin bangō	My Number, the 12-digit Individual Number1

Koseki: citizen-only family register

No koseki is created for a foreign national. When a Japanese national marries a foreign national, the fact of that marriage, including the foreign spouse's name, date of birth, and nationality, is recorded on the Japanese spouse's koseki.³

When the Japanese spouse in such a marriage is not already the head-of-register entry, a new koseki is created with that Japanese national at its head. The 筆頭者 (hittōsha, "head-of-register entry") is the first-listed person whose name and registered domicile identify the register.³

Foreign nationals remain subject to birth and death notification duties for events occurring in Japan. Those filings are preserved as notifications and do not create koseki membership.³

Juminhyo: residence record for all residents

Since July 9, 2012, qualifying foreign residents have been covered by the Basic Resident Register Act on the same footing as Japanese nationals, and they receive a juminhyo.⁴ The city, ward, town, or village office keeps the register and issues certified copies on request.²

A foreign resident's juminhyo carries the standard items plus foreign-specific fields. Standard items include name, birth date, sex, household-head relation, address and move history, My Number, insurance and pension enrollment items where applicable, and the juminhyo code.²

Added fields for mid- to long-term residents include status of residence, period of stay, expiry date, and residence card number. Special permanent residents instead carry special-permanent-resident status and certificate number, and other categories carry fields matching their authorization basis.²

A resident may request a copy of their own juminhyo or that of someone in the same household from the mayor or ward head of the holding municipality. A request by anyone else requires a stated legitimate reason.²

My Number: the cross-agency identifier

My Number is the 12-digit number assigned to every resident holding a juminhyo in Japan.¹ Its use is limited to procedures defined in statute or ordinance in the social security, tax, and disaster-countermeasure fields.¹

Foreign residents holding a juminhyo were notified of My Number in sequence from October 2015, and it became usable in the same administrative procedures from January 2016. Notification first ran through a notification card, then through a personal-number notification letter from May 25, 2020.⁴

Foreign residents holding a juminhyo may apply for a My Number Card by smartphone, computer, photo booth, or mail.⁴ For most foreign residents the card's validity runs to the expiry date of the period of stay or its equivalent, so an applicant nearing expiry should apply after renewal permission arrives.⁴

The juminhyo code and My Number are distinct identifiers. Both appear in the juminhyo item list, but they are not interchangeable.²

How My Number Links the Records

Linkage is statute-controlled lookup between separate holdings, not a merged file. Each agency keeps its own records, and the network carries only what a given procedure is allowed to ask for.

Which records carry My Number

The juminhyo item list includes My Number alongside insurance, pension, child-allowance, and juminhyo-code items.² Tax, pension, and health-insurance procedures sit inside the statutory My Number use fields, so those registries key to My Number where statute permits.¹

The koseki itself is not described in the fetched primaries as holding a My Number field. Linkage to koseki information runs through resident-register-keyed lookup or electronic-certificate presentation instead.⁵⁶

One confirmed example is child-allowance certification. Presenting My Number lets the receiving agency confirm parent-child and marriage-relation information from koseki-related data instead of collecting a koseki certificate.⁵

How linkage works across agencies

Information linkage means administrative bodies exchange procedure-necessary data over a dedicated network system, which lets residents omit document submissions.¹ Personal data is not centrally merged. Pension data stays at the pension office and local-tax data stays at the municipality, with each body keeping its own records.¹

When agencies link data, they use dedicated codes rather than passing My Number itself directly.¹ Collection, storage, use, or provision of My Number-linked personal data beyond what statute prescribes is prohibited. The Personal Information Protection Commission monitors handling, and violations carry heavy penalties.¹

Residents can review their own linkage history online

Residents can review on MynaPortal the history of personal-data exchanges between administrative bodies.¹

What the Linkage Lets You Do

In practice the payoff is twofold: fewer paper attachments, and certificate requests that start online or at a store terminal. Both depend on the specific municipality, so confirm the channel before traveling.

Channel	What it does	Constraint
MynaPortal electronic application	Apply for juminhyo or koseki certificates online, receive paper by mail	Only where the municipality accepts it7
16-digit koseki code	Agency confirms electronic koseki certificate, no paper tohon	Obtain via MynaPortal; documented for passport application6
Konbini multifunction printer	Print koseki or juminhyo certificates with My Number Card	Honseki advance registration required where municipalities differ8
Any-counter wide-area issuance	Request koseki certificates at any municipal counter in person	Eligible requesters only, photo ID required5

Request documents online and at konbini

MynaPortal does not issue juminhyo copies or koseki tohon as PDF or electronic files. In participating municipalities, residents apply electronically and receive the certificate on paper, mainly by mail.⁷

Whether electronic application exists depends on the municipality. If the procedure does not appear in a MynaPortal search for that municipality, that municipality does not accept electronic applications for the certificate.⁷

The 16-digit koseki electronic-certificate provision code can be obtained via MynaPortal and presented at an agency counter or in an online procedure. The agency then confirms the electronic koseki certificate instead of collecting a paper tohon.⁶ The MynaPortal FAQ names passport application as a procedure usable with that code.⁶

Konbini issuance of a honseki-municipality koseki certificate requires a My Number Card. Where the residence municipality and the 本籍 (honseki, "registered domicile") municipality differ, advance use-registration with the honseki municipality comes first.⁸ Both kiosk-terminal and internet routes with a card reader exist for that advance registration.⁸

Authorize cross-agency information transfer

Presenting My Number in procedures such as child-allowance certification lets the receiving agency confirm koseki-relation information directly. The koseki-certificate attachment that was previously required drops away.⁵

In passport issuance, sending the 16-digit koseki electronic-certificate code with the application via MynaPortal lets the agency confirm the electronic certificate. The paper attachment drops away and the procedure completes online.⁵

More broadly, linkage over the dedicated network is what allows omission of attached documents across procedures. Eligible procedures vary, so confirm per-procedure guidance from the municipality or agency before assuming an attachment is unnecessary.¹

Fees and participation for konbini issuance are set locally and vary by municipality (as of 2025-12-25; confirm current figures with your honseki or resident municipality). No single national fee or universal availability applies.⁸

Foreign Residents: My Number Without a Koseki

A foreign resident holds My Number through resident registration, never through koseki membership. That single boundary explains most of the confusion in mixed-nationality households.

My Number on juminhyo but not on koseki

Foreign residents holding a juminhyo were notified of My Number from October 2015 and use it from January 2016 in the same statutory fields.⁴ A foreign resident's juminhyo item list includes My Number as a standard entry.²

No koseki is created for a foreign national, including through marriage to a Japanese national or through long residence. The foreign spouse is recorded only as a marriage fact on the Japanese spouse's koseki.³

What foreign households use instead

Foreign-foreign couples form no koseki. Their registered-residence evidence runs through the juminhyo, plus home-country documents where relationship evidence is required.⁴³

Since the 2012 reform, a mixed Japanese-foreign household can be recorded and certified on a single shared juminhyo.⁴ Ward offices vary in how they format that shared copy, so confirm with the local city or ward office which version a bank or employer expects.

Foreign nationals must still file birth and death notifications in Japan where the event occurs in Japan. Those filings are preserved as notifications and do not create koseki membership.³

Privacy Design: Isolation Preserved in Parts

The system was built to link procedures without pooling personal data. Each protection below is stated on a Digital Agency primary, not inferred from commentary.

Sectoral isolation by design

Agencies keep their own data holdings rather than pooling personal data centrally.¹ Linkage exchanges use dedicated codes, not My Number itself.¹

Access to the systems is restricted to authorized persons, and communications are encrypted.¹ Identity verification, meaning My Number confirmation plus personal-identity confirmation, is mandatory when providing My Number.¹

Oversight sits with the Personal Information Protection Commission as a third-party body. Handling follows its guidelines and protection assessments.¹

My Number use outside statute stays prohibited

Collecting or storing My Number-linked personal data beyond what statute prescribes is prohibited, and violations carry heavy penalties.¹

Accelerated linkage since 2025 within limits

A partial amendment to the My Number Act and the Basic Resident Register Act, promulgated May 23, 2025, expanded My Number-usable affairs. The expansion covers national-qualification affairs across 44 qualifications plus 12 additional affairs.¹

The Digital Agency positions that expansion as efficiency and convenience improvement within statutory use limits. The same page retains the dispersed-management and code-based linkage design described above.¹

Koseki-side digitization linkage also advanced earlier. From March 1, 2024, wide-area issuance lets an eligible requester obtain koseki and removed-register certificates at any municipal counter nationwide.⁵

Wide-area issuance is counter-only and in person by the eligible requester. It is not available by mail or through a proxy, and photo ID such as a driver licence, My Number Card, or passport is required.⁵ It covers koseki and removed-register certificates but excludes partial-matter and individual-matter certificates.⁵

Good to know

Koseki issuance still depends on your honseki municipality

Requesting a honseki koseki at a konbini without advance registration fails at the terminal. Where residence and honseki municipalities differ, the honseki municipality requires use-registration before any konbini koseki certificate is dispensed, and registration accepts a My Number Card only.⁸

Every municipality does not offer the same issuance channels. MynaPortal electronic applications exist only where the municipality accepts them, and konbini issuance works only where the honseki municipality participates. Search MynaPortal or the J-LIS municipality list for the specific municipality before traveling.⁷⁸

A juminhyo copy with My Number has stricter pickup rules

Expecting a My Number-included copy instantly through any channel causes delays. MynaPortal issues certificates on paper by mail rather than as immediate PDFs, so online application adds mail time rather than removing it.⁷

Requesting another person's koseki or juminhyo without checking eligibility also fails. Juminhyo copies for non-household requesters require a stated legitimate reason, and wide-area koseki issuance is limited to the person, spouse, and direct ascendants or descendants appearing in person.²⁵

Linkage does not merge the registers

Treating My Number as a replacement for the koseki or juminhyo misreads the design. The registers stay separate under dispersed management, and linkage only exchanges procedure-necessary data over the dedicated network.¹⁵⁶

Presenting My Number or a 16-digit code removes a specific attachment. It does not create a single combined record, and a counter that needs a different certificate will still ask for it.¹⁵

See also

• Koseki: Japan's Family Register Explained
• Jūminhyō: Japan's Residence Record Explained
• How to Request Koseki and Juminhyo Copies
• Foreigner on Koseki Edge Cases
• Citizenship for Children Born in Japan
• My Number Reporting for Bank Accounts

References

Footnotes

1. デジタル庁 (Digital Agency). 「マイナンバー制度とは」. https://www.digital.go.jp/policies/mynumber/explanation/ ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹ ↩²⁰ ↩²¹ ↩²² ↩²³ ↩²⁴

2. 総務省 (MIC). 「外国人住民に係る住基台帳制度｜住民票」. https://www.soumu.go.jp/main_sosiki/jichi_gyousei/c-gyousei/zairyu/resident_record.html ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰

3. 法務省 (Ministry of Justice). 「国際結婚、海外での出生等に関する戸籍Q&A」. https://www.moj.go.jp/MINJI/minji15.html ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸

4. 総務省 (Ministry of Internal Affairs and Communications, MIC). 「外国人住民に係る住民基本台帳制度」 (index page). https://www.soumu.go.jp/main_sosiki/jichi_gyousei/c-gyousei/zairyu/index.html ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷

5. 法務省 (Ministry of Justice, Civil Affairs Bureau). 「戸籍法の一部を改正する法律について（令和6年3月1日施行）」. https://www.moj.go.jp/MINJI/minji04_00082.html ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹

6. マイナポータル (MynaPortal, Digital Agency). 「戸籍電子証明書提供用識別符号とは何ですか。」 FAQ No. 10678. https://faq.myna.go.jp/faq/show/10678?site_domain=default ↩ ↩² ↩³ ↩⁴ ↩⁵

7. マイナポータル (MynaPortal, Digital Agency). 「マイナポータルで戸籍謄本（全部事項証明書）や住民票を取得できますか。」 FAQ No. 8044. https://faq.myna.go.jp/faq/show/8044?site_domain=default ↩ ↩² ↩³ ↩⁴ ↩⁵

8. 地方公共団体情報システム機構 (J-LIS). 「コンビニエンスストア等における証明書等の自動交付【コンビニ交付】：本籍地の戸籍証明書取得方法」. https://www.lg-waps.go.jp/01-06.html ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶