Choosing Surnames in International Marriages
Choosing surnames in international marriages works differently from what most couples expect from Japan's reputation for shared surnames. By default, each spouse keeps their own name, and sharing one name takes a separate procedure whose route depends on which spouse changes and when.1
Procedures, fees, and requirements can change. Confirm current details at the Ministry of Justice family register guidance and the courts' surname-change procedure page. This article is general information, not legal advice; for your specific case, consult a licensed gyoseishoshi for a filing read, or a family-law attorney for a contested or unusual name-change petition.
Overview
Japan's single-surname rule applies to marriages between two Japanese nationals, who must adopt one shared surname at marriage.2 When one spouse is a foreign national, that rule does not engage, so the couple holds separate surnames from the start unless someone acts.13
This article covers both halves in order: what the Japanese spouse can do, what the foreign spouse can do, and how children and records follow. The key terms recur throughout:
| Japanese term | Romaji | English gloss |
|---|---|---|
| 戸籍 | koseki | Family register, the citizen-only household register1 |
| 氏 | shi (uji) | Surname, family name as registered on the koseki4 |
| 婚姻届 | konin todoke | Marriage registration form1 |
| 通称 | tsūshō | Registered alias (common name) on a foreign resident's resident record5 |
| 家庭裁判所 | katei saibansho | Family court, which grants permission for surname changes outside the six-month window6 |
The Default Rule: Separate Surnames
Couples in which one spouse is Japanese and the other is foreign start married life with two surnames. No filing creates this outcome and no filing is needed to keep it.1
Why Article 750 Does Not Apply
Civil Code Article 750 provides that a husband and wife shall adopt the surname of either spouse as decided at marriage.2 In registration practice this provision governs marriages between Japanese nationals. A Japanese national who marries a foreign national keeps their pre-marriage surname automatically, because the foreign spouse has no koseki and the one-register-one-surname structure has nothing to merge.13
Professional commentary grounds this in the treatment of surnames as a personal matter decided under each spouse's own national law.3 The practical result is simple: the marriage itself changes nobody's name.
How the Marriage Appears on the Records
No koseki is created for the foreign spouse. Instead, the Japanese spouse's koseki records the foreign spouse's name, date of birth, and nationality alongside the fact of the marriage.1 If the Japanese spouse is not already the head of a koseki, a new one is created with that spouse as head at this point.14
The foreign spouse's residence card and passport continue to show the foreign spouse's own name. The residence card lists whatever name the holder lawfully uses, and any lawful name change must be reported to immigration within 14 days with supporting documents.7
Options for the Japanese Spouse
The Japanese spouse has three paths: do nothing, file a simple notification within six months, or seek court permission afterward. The decision tree looks like this:
Keep Your Pre-Marriage Surname (No Action Needed)
Keeping your name requires no visit and no form. The koseki update recording the marriage happens through the marriage filing itself, and your registered surname stays exactly as it was.1
This is the path most couples end up on, since sharing a name demands a deliberate second step. Nothing about residence cards, passports, or daily paperwork forces the issue later.
Adopt Your Spouse's Surname Within Six Months
Within six months of the day the marriage took effect, you may change to your spouse's surname by filing a notification of surname change at the municipal koseki counter. No family-court permission is needed in this window (Family Register Act Article 107, paragraph 2).143
The change takes effect only when this notification is submitted. Practitioner guidance flags a common misunderstanding here: writing the foreign surname in the marriage-notice form's surname column has no legal effect on its own.3
If you wrote your spouse's surname on the marriage notice expecting your registered name to follow, it did not. File the separate surname-change notification within the six-month window to make the change real.3
After the notification, the registered name takes the form of the foreign surname plus the given name. The Ministry of Justice illustrates this with a Japanese spouse becoming ジョーダンあゆ美 after marrying Carlos Jordan.1 The foreign surname enters the register in Japanese script, so the katakana rendering you choose at filing becomes the registered form.8
Adopt After Six Months, or a Compound or Differing Form
Once six months have passed since the marriage took effect, changing to your spouse's surname requires family-court permission first, followed by the municipal notification.16 The court's stated standard is unavoidable circumstances, meaning cases where leaving the surname unchanged causes significant difficulty in social life.6
In practice, practitioner sources describe marriage-based petitions as routinely granted absent long post-marriage delay. The petition names the wish to take the foreign spouse's surname as the reason, and the court may ask for the foreign spouse's resident record among the supporting documents.69 Treat the practical pattern as reassuring background, not as a lighter legal test: the standard on the books is the general one.
Some wishes always need court permission, even within six months. A compound surname combining both spouses' names, your spouse's registered alias rather than their legal surname, or only part of a spouse's surname falls outside the six-month notification, which covers only the spouse's registered surname as recorded.9
Combining your name with your spouse's into a new double surname is never a counter-only filing. Plan for a court petition whatever the calendar says.9
Filing the petition costs 800 yen in revenue stamps plus postage set by each court (as of 2026-09-08; confirm current figures with the family court hearing your case).6 Court review adds weeks that the counter notification does not, which is the real price of missing the window.
| Item | Amount | As of | Notes |
|---|---|---|---|
| Family-court surname-change petition | ¥800 revenue stamps plus postage (varies by court) | 2026-09-086 | Postage set by each court |
| Municipal surname-change notification within six months | No fee stated in primary sources | n/a | Counter filing at the koseki office1 |
The table above reflects figures current as of the dates shown (as of 2026-09-08).6
Options for the Foreign Spouse
The foreign spouse's side follows a different logic, because Japanese law provides no procedure for changing a foreigner's surname. Whether you can adopt your spouse's Japanese surname is decided under your own home-country law, so the answer varies by nationality.3
Keep Your Pre-Marriage Surname (Default)
Japan's single-surname rule does not bind you, so keeping your name needs no action.13 Your residence card and passport stay in your own name, and the Japanese-side koseki simply records you under that name as the Japanese spouse's partner.17
Adopt Your Spouse's Japanese Surname via Home-Country Procedure
Where your home country's law permits a marriage-based surname change, complete that country's procedure first.3 Japan cannot grant what only your national law can create, and municipal offices will ask for proof that the change already happened abroad.
The Japanese spouse then brings proof of the change to the municipal office to correct the koseki marriage entry. In principle this means an official home-country document showing the names before and after, the reason, and the date; where no such certificate exists, a copy of the renewed passport showing the new name is accepted.3 Confirm with the specific municipal office which proof it wants before you go, since counters exercise discretion here.
After the home-country change, report the new name to immigration within 14 days. For a marriage to a Japanese national, bring the updated passport and the marriage certificate, which in practice means a koseki transcript.7
Immigration asks for the passport already showing the new name, so a trip to the municipal office alone does not finish the job. Without the renewed passport on hand, same-day reissue of the residence card may not be possible.7
Use a Japanese Surname as a Registered Alias Without a Legal Change
If your home country's law offers no marriage-based change, or you simply prefer not to alter your legal name, you may register your spouse's Japanese surname as a 通称 (tsūshō, registered alias) at your municipal office.58 The alias appears alongside your legal name on your resident record and can be used for daily matters in Japan such as a driver's licence, health insurance, and contracts.58 It does not appear on your residence card, which continues to show your legal name alone.8
Understand the boundary clearly. An alias is for life in Japan only: it does not appear in your passport, it does not change your home-country records, and offices outside Japan do not recognize it.8 Whether a bank or agency accepts the alias for a given transaction is decided institution by institution, so ask before assuming.
Children and the Family Surname
A child of an international couple takes the Japanese parent's current koseki surname. If the Japanese spouse changed to the foreign surname before the birth, the child receives that surname with no further procedure; if the Japanese parent kept a Japanese surname, the child receives that Japanese surname by default.8
Changing a child's registered surname afterward requires a separate family-court step.8 Resident guidance describes this step as repeating per child, but with only one secondary source behind that detail, treat the per-child repetition as something to confirm with the court rather than a settled rule. A child who is not the koseki head or head's spouse and has a foreign parent may also petition to take the foreign parent's surname with court permission.6
Good to know
The Six-Month Clock Starts on the Day the Marriage Takes Effect
The window runs from the date the marriage became effective, not from any later paperwork date. For a marriage formed abroad under foreign law, that means the date it became effective in that country, which Japan asks you to report within three months.1
Couples who marry abroad and settle the Japanese paperwork later can therefore arrive at the counter with less of the window left than they assumed. Calendar the deadline from the foreign effective date, and file the surname notification early if sharing a name matters to you.
A Foreign Surname Enters the Koseki in Japanese Script
Only Japanese script can head a koseki entry, so a foreign surname must be rendered in katakana (or kanji where the characters genuinely apply). The roman-letter original cannot stand as the registered form.8
Choose the rendering deliberately, checking how it reads back in the other language. Two transliterations of one name can look and sound like different names to different readers, and this spelling follows the family afterward.
Writing a Name in the Marriage-Notice Surname Column Changes Nothing by Itself
Some couples assume the marriage notice settles the surname question because the form has a surname field. It does not; practitioner guidance singles this out as the most common misunderstanding in the whole procedure.3
Only the separate surname-change notification, or the court route when the window or the wish falls outside it, changes the registered surname. If months have passed and the register still shows the old name, this is almost certainly why.
Confirm Alias and Proof-of-Change Handling With Your Ward Office
Municipal counters differ in how they handle alias registration and which proof of a foreign name change they accept. The courts' own guidance says a foreign spouse's resident record "may" be requested, which signals office-level discretion rather than a uniform checklist.65
Treat ward-specific blog walkthroughs as illustrations, not promises. A short confirmation call to the office where you will file settles what that counter wants.
See also
- Koseki: Japan's Family Register Explained
- Marriage to a Japanese National
- Jūminhyō: Japan's Residence Record Explained
- Citizenship for Children Born in Japan
- Marriage Between Two Foreigners in Japan
- Domestic Partnerships and the Future of Marriage Law