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Claim for Judicial Acknowledgment of Paternity | A Supreme Court Judgment Holding That a Child Born Out of Wedlock May Also Claim Past Support From the Biological Father

This is a case in which the issue was whether, through a claim for judicial acknowledgment of paternity, a child born out of wedlock could claim past support from the biological father after reaching the age of majority. (Supreme Court, Judgment of September 11, 2025, 2023 Meu 11758)

CONTENTS
  • 1. Overview of the Claim for Judicial Acknowledgment of Paternity Case
  • 2. The First-Instance Court's Determination on the Claim for Judicial Acknowledgment of Paternity
    • - The Appellate Court's Determination on the Claim for Judicial Acknowledgment of Paternity
  • 3. The Supreme Court's Determination on the Claim for Judicial Acknowledgment of Paternity
    • - The Significance of This Judgment
  • 4. Daeryun's Strategy Regarding the Claim for Judicial Acknowledgment of Paternity

1. Overview of the Claim for Judicial Acknowledgment of Paternity Case

The plaintiff in this case, who filed a claim for judicial acknowledgment of paternity, was a child born out of wedlock and sought to claim past support from the biological father.

The defendant in this case, the plaintiff's biological father, had the plaintiff with another woman during his marriage.

At the time of birth, the defendant and the plaintiff's mother prepared a written agreement on the payment of child support, which provided that the defendant would have no obligation to pay child support after paying a certain amount.

Subsequently, through a separate conciliation, the defendant agreed not to bear responsibility for raising the plaintiff, and the mother solely raised the plaintiff until the plaintiff reached the age of majority.

Upon reaching the age of majority, the plaintiff filed a claim for judicial acknowledgment of paternity against the defendant together with a claim for the payment of past support.

This was a request to recover the child support that the plaintiff had actually needed during the period of minority, regardless of the mother's agreement or waiver.

2. The First-Instance Court's Determination on the Claim for Judicial Acknowledgment of Paternity

The first-instance court determined that even if one parent agreed not to claim child support, this does not extinguish the right to claim support, which is a right inherent to the minor child.

In particular, it applied the legal principle that, because a judgment of acknowledgment takes effect retroactively to the time of birth, the child may claim support from the person bound to provide it even for support that accrued before the acknowledgment became final.

Accordingly, the court held that the defendant must pay the plaintiff KRW 70 million in past support.

The Appellate Court's Determination on the Claim for Judicial Acknowledgment of Paternity

The appellate court also upheld the lower judgment as it stood.

The court emphasized that an agreement made by the parents is without effect where it is contrary to the welfare of the child, and that the duty of support is an absolute obligation arising from the essential nature of the parent-child relationship.

Therefore, it held that even if one parent had in fact supported the child, the other parent is not relieved of responsibility.

3. The Supreme Court's Determination on the Claim for Judicial Acknowledgment of Paternity

The Supreme Court's Determination on the Claim for Judicial Acknowledgment of Paternity

The Supreme Court upheld the lower judgment as it stood and dismissed the defendant's final appeal.

▶Key Points of the Supreme Court's Determination

1. Limited Effect of an Agreement Waiving Child Support

The Supreme Court determined that even if the parents agree to waive the right to claim future child support, this does not affect the child's inherent right.

Accordingly, it held that an agreement contrary to the welfare of the child is void.

2. Retroactive Effect of Acknowledgment

Under Article 860 of the Civil Act, acknowledgment takes effect retroactively to the time of birth.

Accordingly, the court held that even before the judgment of acknowledgment becomes final, the child may have the right to claim support from the biological father from the time of birth.

3. Past Support May Be Claimed

A child born out of wedlock may claim the past child support that accrued during the period of minority, taking into account circumstances such as the biological father's assets and income.

Accordingly, the court held that the conclusion is no different even where the child had already received actual support from the mother.

The Significance of This Judgment

· Strengthening the Rights of a Child Born Out of Wedlock

This judgment gave priority to the rights of a child born out of wedlock over the agreement of the parents. It reaffirms the basic principle of the Family Litigation Act, namely the protection of the welfare of the child.

· Emphasizing the Essential Nature of the Duty of Support

It made clear that a claim for child support is an obligation that naturally arises from the parent-child relationship, regardless of whether parental authority is exercised or who holds custody.

· Setting an Important Standard for Practice

Cases in which a child born out of wedlock reaches the age of majority and claims past support may increase going forward, and this precedent is a representative case showing the standard by which courts will make their determinations.

· A Judgment Centered on the Welfare of the Child

It carries significant social meaning in that it clarified that the welfare of the child, rather than an agreement between the parents, must be given the highest consideration.

4. Daeryun's Strategy Regarding the Claim for Judicial Acknowledgment of Paternity

Based on this precedent, Daeryun Law Firm LLP proposes the following strategy in cases involving a claim for judicial acknowledgment of paternity.

① Detailed Analysis of the Facts

We closely review the child's birth, whether the parents were married, the content of any past agreements, and similar matters.

In particular, we analyze the effect that a past child support agreement has on the child's rights.

② Use of the Retroactive Effect of Acknowledgment
We actively assert the provision of Article 860 of the Civil Act, under which a judgment of acknowledgment takes effect retroactively to the time of birth once it becomes final, thereby making a claim for past support possible.

③ Securing the Basis for Calculating Support
We calculate the amount of the support claim by comprehensively considering the parents' income and asset levels, their standard of living, the costs actually incurred in raising the child, and similar factors.

Because courts make their determinations based on the welfare of the child, documentary evidence of specific expenditures is important.

④ Defense Strategy (for the Defendant)
Where the amount of the support claim is excessive, the defendant may seek a reduction by asserting that one parent has already provided substantial support.

The defendant may also reduce liability by proving special circumstances, such as financial ruin or a long-term contribution of actual support.


A claim for judicial acknowledgment of paternity goes beyond confirming the parent-child relationship and is directly connected to a claim for past child support, so it is a complex matter in which both proof of the facts and the application of legal principles are important.

Daeryun Law Firm LLP protects clients' rights through collaboration among attorneys handling family law matters and its Evidence Investigation Center and Digital Forensics Center.

If you need related assistance, you are welcome to make a 🔗legal consultation reservation with Daeryun Law Firm LLP.

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