The Short Answer
Yes, if the father admits in writing that the child is his. Under Republic Act No. 9255 (RA 9255), a child born outside marriage may use the father's surname once he has recognized the child, on the Birth Certificate or in a signed admission, and an Affidavit to Use the Surname of the Father (AUSF) is filed with the civil registrar. The child stays illegitimate (born outside marriage) and remains under the mother's parental authority (her legal right and duty to decide for the child). If the parents later marry each other and had no legal impediment (a legal reason they could not marry, such as already being married to someone else) when the child was conceived, the child can be legitimated, which makes them legitimate.
Example: Baby Miguel of Tacloban
Names and details in this example are made up.
Liza Santos and Paolo Reyes, both single, live together in Barangay 77, Tacloban City. Their son Miguel was born on 4 February 2025 at the Eastern Visayas Medical Center. Paolo was working in Manila when Miguel was born, so he did not sign the Certificate of Live Birth. Miguel was registered as Miguel Santos.
Step 1: Paolo acknowledges Miguel. When he comes home, Paolo signs a notarized Affidavit of Admission of Paternity stating that he is Miguel's father.
Step 2: the AUSF. Miguel is under seven, so Liza signs the AUSF, as his mother. It is also notarized. If Miguel were already 10, he would sign it himself, with Liza attesting (confirming it).
Step 3: filing. Liza brings both affidavits, a copy of Miguel's Birth Certificate and their IDs to the Tacloban City Civil Registry, where the birth was registered, and pays the office's filing fee. The registrar checks that the names, dates and places match on every paper.
Step 4: the PSA copy. Once the papers reach the PSA, Miguel's PSA Birth Certificate carries an annotation (a note on the record) that he uses the surname Reyes. From then on he is Miguel Reyes in school and on his passport. He is still a child born outside marriage, and Liza still has parental authority over him.
Later: if Liza and Paolo marry. Say they marry in 2027. Neither was married to anyone else when Miguel was conceived, so there was no impediment. After the wedding they sign a Joint Affidavit of Legitimation and register it with the Tacloban City Civil Registry. Miguel then becomes a legitimate child, with the same rights as a child born in the marriage, counted from his birth.
What if Paolo had still been married to someone else? Then Miguel can still use the Reyes surname through the same acknowledgment and AUSF. But a later marriage of Liza and Paolo would not legitimate him, because Paolo could not marry Liza when Miguel was conceived.
Three Ways the Father Can Acknowledge the Child
Under Article 176 of the Family Code, as amended by RA 9255, the father must expressly recognize the child in one of these ways:
- On the birth record. He signs the acknowledgment on the Certificate of Live Birth, usually at the hospital or when the birth is registered.
- In a public document. A notarized affidavit admitting paternity, such as an Affidavit of Admission of Paternity or Affidavit of Acknowledgment.
- In a private handwritten instrument. A document he wrote and signed in his own hand, admitting he is the father. Under the RA 9255 rules, he must file it personally while he is alive. If he has died, the mother, the child if of age, or the guardian may file it with other documents proving filiation (that he is the father).
Without one of these, the civil registrar cannot put the father's surname on the record. If the father refuses to acknowledge the child, paternity has to be proven in court.
The AUSF, in Short
Acknowledgment alone does not change the surname. The Affidavit to Use the Surname of the Father (AUSF) does. Under the RA 9255 rules, who signs it depends on the child's age: the mother (or the guardian if the mother is not available) for a child aged 0 to 6; the child, with full awareness of what it means and with the mother or guardian attesting (confirming), for ages 7 to 17; and the child alone at 18 and over.
It is filed with the local civil registry office where the birth was registered, or with the Philippine embassy or consulate if the papers are signed abroad.
For the steps and papers, see using the father's surname for a child born outside marriage.
What Changes, and What Does Not
- The surname changes on the record, through an annotation on the PSA Birth Certificate.
- The status does not. The child is still a child born outside marriage. Using the father's surname does not make them legitimate.
- Parental authority stays with the mother (Family Code, Art. 176). The father does not gain custody by giving his surname.
- Filiation is established. Acknowledgment matters for support and inheritance. A child born outside marriage inherits half the share of a legitimate child.
- It is optional. The law says the child may use the father's surname. An acknowledged child keeps the mother's surname if no AUSF is filed.
If You Marry Later: Legitimation
Under Articles 177 and 178 of the Family Code, as amended by Republic Act No. 9858 (RA 9858), a child born before the parents married becomes legitimate through their later valid marriage to each other, if, when the child was conceived, the parents had no legal impediment to marry each other, or the only impediment was that one or both were under 18.
After the wedding, both parents sign a Joint Affidavit of Legitimation and register it with the civil registry of the place of birth within 30 days. The child then has the same rights as a legitimate child, from birth. See legitimation.
| Route | When It Fits | Child's Status After |
|---|---|---|
| Acknowledgment and AUSF (RA 9255) | The father acknowledges the child, married to the mother or not | Still illegitimate |
| Legitimation (RA 9858) | The parents later marry each other and had no impediment, other than age, at conception | Legitimate |
Common Questions
Ayaw Pumirma ng Tatay. Puwede Ko bang Ilagay ang Apelyido Niya?
No. The civil registrar needs the father's own acknowledgment: his signature on the birth record, a notarized admission, or a document handwritten and signed by him. If he refuses, the child uses your surname, and paternity can only be established through a court case.
Nasa Abroad ang Tatay. Kailangan pa ba Siyang Umuwi?
Not necessarily. He can sign an affidavit admitting paternity before a Philippine embassy or consulate, or before a local notary abroad followed by an apostille. Ask the civil registrar which form it accepts. See the guide on apostille.
Can the Father Take My Child Because the Child Now Uses His Surname?
No. Under Article 176 of the Family Code, parental authority over a child born outside marriage stays with the mother. Using the father's surname does not change that.
Can the Father Force My Child to Use His Surname?
No. The law says the child may use it. It is not required, and an acknowledged child keeps the mother's surname if no AUSF is filed.
I Was Still Married to Someone Else When My Child Was Born. Can the Child Use the Biological Father's Surname?
This is more complicated. A child born to a married woman is presumed to be the legitimate child of her husband, and only the husband, or in some cases his heirs, can challenge that in court within short deadlines. The civil registrar generally cannot record another man as the father on its own. This needs a lawyer. The Public Attorney's Office (PAO) helps people who qualify.
Not legal advice. This is general information. For advice on your own situation, consult a lawyer. If you cannot afford one, the Public Attorney's Office (PAO) or an IBP legal aid office may help for free.
Government fees, rules and requirements change, so always check with the office concerned before you go. This page explains the general rules; it cannot tell you how they apply to your own family or case. Last reviewed October 8, 2026.