Using the Father's Surname for a Child Born Outside Marriage

What the Law Says

Article 176 of the Family Code, as amended by RA 9255, says children born outside marriage use the surname of their mother and are under her parental authority. They may use the surname of their father if he has clearly recognized them:

• through the record of birth in the civil register (for example, he signed the acknowledgment on the Certificate of Live Birth);
• through an admission in a public document, such as a notarized Affidavit of Admission of Paternity or Affidavit of Acknowledgment; or
• through a private handwritten instrument (PHI), a document written and signed in his own hand admitting he is the father.

The law uses "may": it is an option, not a requirement. The father keeps the right to go to court during his lifetime to prove he is not the father.

The Documents Involved

• Affidavit of Admission of Paternity (or Affidavit of Acknowledgment): the father's sworn admission that he is the father. It is a notarized affidavit.
• Private handwritten instrument: under the RA 9255 rules, the father must file it personally. If he has died, the mother, the child if of age, or the guardian may file it with other documents proving he is the father (filiation).
• Affidavit to Use the Surname of the Father (AUSF): the affidavit that actually asks for the child to use the father's surname. It is a registrable document (one the civil registry records). Without it, an acknowledged child keeps the mother's surname.

The AUSF and the acknowledgment are registered together with the Certificate of Live Birth (or the Report of Birth, if the child was born abroad). The rules say they should be registered within 20 days of signing; later filings follow the rules on delayed registration.

Who Signs the AUSF

Under the implementing rules of RA 9255, it depends on the child's age when the AUSF is signed:

The acknowledgment and AUSF may be filed by the father, the mother, the child if of age, or the guardian.

Where to File

• Born in the Philippines, papers signed in the Philippines: the local civil registry office of the place of birth (where the birth was registered).
• Papers signed abroad: the Philippine embassy or consulate in the country where you live, or the nearest one.
• Born abroad, papers signed in the Philippines: the local civil registry office of the place where the papers were signed.

The registrar checks the Birth Certificate and the affidavits. Papers with inconsistent details (names, dates, places) are not accepted, so check them carefully before notarizing. Once registered, the PSA copy of the Birth Certificate gets a note (annotation) showing the child uses the father's surname.

Ask the civil registry for its filing fee and the forms it uses. If the birth was never registered, start with late registration of birth.

What Changes and What Does Not

• The child's surname changes on the record, through an annotation.
• The child is still a child born outside marriage. Using the father's surname does not make them legitimate.
• Under Article 176, parental authority stays with the mother.
• Acknowledgment legally establishes that he is the father (filiation), which matters for support and inheritance. Article 176 sets the legitime (forced share) of each such child at one half of that of a legitimate child.

If the parents later marry each other, the child may be legitimated (made legitimate) in some cases. That is a separate process at the civil registrar. If someone disputes who the father is, the matter goes to court, and you will need a lawyer. The Public Attorney's Office (PAO) helps people who qualify.