As a general rule, illegitimate children use the surname of their mother. However, Republic Act No. 9255 amended the law to allow an illegitimate child to use the surname of the father if the father has expressly recognized the child. Recognition may be shown through the record of birth appearing in the civil register, an admission of paternity in a public document, or a private handwritten instrument signed by the father, or when the father acknowledges the child in the affidavit provided for the purpose (the Affidavit to Use the Surname of the Father, or AUSF). The use of the father's surname is permissive, not compulsory: it does not by itself make the child legitimate, and it does not automatically transfer parental authority (which remains with the mother for an illegitimate child), though it does establish filiation for purposes such as support and succession. The Supreme Court has clarified that even where the father has recognized the child, the child (through the mother, if a minor) is not compelled to use the father's surname; the word used in the law is permissive. The change of surname is generally processed administratively with the local civil registrar with the required documents, rather than through a court case. So an illegitimate child may bear the father's surname when he acknowledges the child, but the mother's surname remains the default and the choice is not forced.
The Default and the Exception
Illegitimate children generally use the mother's surname. Under RA 9255, the child may use the father's surname if the father has expressly recognized the child.
How Recognition Is Shown
- The record of birth in the civil register;
- An admission of paternity in a public document;
- A private handwritten instrument signed by the father; or
- The Affidavit to Use the Surname of the Father (AUSF).
Permissive, Not Compulsory
Using the father's surname is permissive — it does not make the child legitimate or transfer parental authority (which stays with the mother), though it establishes filiation for support and succession. Processed administratively with the registrar.
Practical Takeaways
- Default is the mother's surname;
- The father's surname may be used if he recognizes the child;
- It is optional and does not confer legitimacy or parental authority.
Frequently Asked Questions
What surname does an illegitimate child use? As a general rule, the mother's surname. Under RA 9255, the child may use the father's surname if the father has expressly recognized the child.
How does a father recognize an illegitimate child for surname use? Through the record of birth in the civil register, an admission of paternity in a public document, a private handwritten instrument signed by him, or the Affidavit to Use the Surname of the Father (AUSF).
Does using the father's surname make the child legitimate? No. The use of the father's surname is permissive and does not by itself make the child legitimate or transfer parental authority, though it establishes filiation for support and succession.
Is the child forced to use the father's surname if recognized? No. The Supreme Court has clarified that the law is permissive, so even where the father has recognized the child, the child is not compelled to use the father's surname.
This commentary is for general informational purposes only and does not constitute legal advice. For guidance specific to your situation, please consult a licensed attorney.
If you have questions about your rights or options under Philippine law, our firm is available to assist. You may reach us via Viber or WhatsApp, call us at 0995 433 5550, or send an email to vivasnobles@gmail.com. We look forward to hearing from you.