JapanWhat is legitimacy presumption? How to deny paternity?
In Japan, legitimacy presumption means a child born to a married woman is legally presumed to be her husband’s child. Paternity can be denied by the husband filing a 'denial of paternity' action within one year of learning of the birth.
What the Law Says
Japanese law presumes that a child born to a married woman is the legitimate child of her husband. This presumption protects family stability but can be challenged under strict conditions.
Under Article 772 of the Japanese Civil Code, a child conceived or born during marriage is presumed to be the child of the husband. This applies even if the husband is not the biological father.
The husband may deny paternity by filing a 'denial of paternity' action in family court. However, this right is strictly time-limited: he must file within one year of becoming aware of the child’s birth (Article 774).
The denial action does not require genetic testing — courts decide based on evidence such as cohabitation, opportunity for conception, and credibility of statements. Once the one-year deadline passes, the presumption becomes irrefutable.
Importantly, only the husband may file this action — the wife, child, or alleged biological father cannot initiate it. The child acquires Japanese nationality and inheritance rights upon recognition as legitimate.
Statutory TextA child conceived by a wife during marriage shall be deemed the child of the husband.
— Civil Code, Art. 772 — Legitimacy of child born to married woman
Statutory TextThe husband may institute an action to deny paternity within one year from the time he learns of the birth of the child.
— Civil Code, Art. 774 — Action to deny paternity
What to Do
Confirm the child was born during marriage (triggers Article 772 presumption)
Identify the exact date you first learned of the child’s birth
File a petition for denial of paternity at the competent family court within one year of that date
Prepare evidence showing lack of opportunity for conception (e.g., separation, overseas work, medical records)
Attend court hearings; note that genetic testing is not mandatory but may be ordered at the court’s discretion
Sources
Not legal advice. This article is general information based on publicly available sources, written for educational purposes. Laws change and individual situations vary. Consult a licensed attorney in your jurisdiction before acting on anything you read here. Last reviewed: 2026-06-08.