Changing a Child’s Surname When the Man Is Not the Biological Father (Philippines)

This is a practical, Philippine-specific explainer. It’s general information, not legal advice for your specific case.

The short version

You cannot lawfully put a non-biological father’s surname on a child’s birth record just by signing an affidavit or “consenting.”
For illegitimate children (parents not married): the default surname is the mother’s. The child may use the biological father’s surname only if paternity is established under the law. A non-bio father can’t do this.
For legitimate children (born during a valid marriage): the child ordinarily bears the husband’s surname by law. Changing that—because the husband isn’t the bio dad—requires court action to defeat the presumption of legitimacy; it’s a narrow, time-bound remedy.
The proper, clean, durable way for a stepfather (or any non-bio father) to give his surname to a child is adoption. Since 2022, most domestic adoptions are administrative (not court-based) under the National Authority for Child Care (NACC).
If a wrong surname or an invalid “acknowledgment” is already on record, fixes usually run through Rule 108 (cancellation/correction of civil registry entries) or adoption, not through the clerical-error law.

The legal backbone (what controls surnames)

Family Code of the Philippines (EO 209)
- Legitimacy + surname. A child born during a valid marriage is legitimate and normally uses the husband’s surname due to the presumption of paternity.
- Impugning legitimacy (to remove the husband’s surname) is a special, time-limited action available mainly to the husband (or his heirs in limited cases) on specific grounds. It’s not a general “everyone can sue” remedy and is strictly construed.
RA 9255 (2004) – Use of the Father’s Surname by an Illegitimate Child
- An illegitimate child (default: mother’s surname) may use the biological father’s surname only if filiation is established (e.g., Affidavit of Admission of Paternity (AAP), a private handwritten admission, or a court finding), and accompanied by an Affidavit to Use the Surname of the Father (AUSF).
- Key limit: It’s for biological fathers. Using it for a non-bio father is improper and may constitute falsification.
RA 11642 (2022) – Domestic Administrative Adoption and Alternative Child Care Act
- Most domestic adoptions—including step-parent adoption—are now handled administratively by the NACC (not by regular courts).
- An Order of Adoption amends the PSA birth record, substitutes the adopter(s) as parent(s), and changes the child’s surname to the adopter’s, with full legal effect.
Rules of Court
- Rule 103 (Change of Name). A court may allow surname changes for proper and reasonable cause (e.g., to avoid confusion), but courts disfavor using Rule 103 to bypass filiation/adoption rules. It’s not a shortcut to put a stepfather’s surname without adoption.
- Rule 108 (Cancellation/Correction of Entries). Used to correct or cancel substantial civil registry entries (e.g., remove an invalid acknowledgment or wrong father’s name/surname). Requires notice and hearing; evidence (e.g., DNA) is often critical.
RA 9048 (as amended by RA 10172) – Clerical Error Law
- Does not generally allow changing a surname (except very narrow “clerical” cases). Don’t count on RA 9048 to swap a child’s surname from X to Y.

Start with the child’s status at birth

A) Parents not married (illegitimate child)

Default surname: the mother’s.
Can the child use the non-bio father’s surname? No. RA 9255 is only for the biological father (proved via AAP/handwritten admission/court ruling), plus an AUSF.
How can a stepfather give his surname? Adoption (step-parent adoption via NACC). The Order of Adoption will:
1. designate the stepfather as a parent;
2. change the child’s surname to the stepfather’s;
3. trigger issuance of an amended PSA birth certificate.

B) Child born during a valid marriage (legitimate child)

Default surname: the husband’s (presumed father by law).
If husband isn’t the bio father, can we switch to the boyfriend/biological father’s surname? Not by affidavits. The usual path is:
1. Impugning legitimacy (strictly limited—primarily the husband’s action, within set deadlines).
2. If legitimacy is defeated and the child becomes legally “illegitimate” with respect to the husband, you can then establish filiation with the biological father (paternity action, DNA) and use RA 9255, or proceed with adoption (depending on aims).
Adoption by the biological father is generally not a tool to replace the husband’s legal paternity of a legitimate child. You must resolve legitimacy first.

Common real-world situations & clean legal routes

Stepparent wants the child to carry his surname (he isn’t the bio Dad). → Step-parent adoption (RA 11642). What to expect: file with NACC Regional Office; social worker case study; consents (spouse; child if 10+; biological parent(s) unless excused by law due to abandonment/termination of parental authority); possible supervised trial custody; Order of Adoption issued by NACC; PSA issues amended birth certificate with the stepfather’s surname.
Child currently bears a non-bio father’s surname because someone signed papers in the past. → If that “admission” was invalid (e.g., signer not the bio father), you typically file a Rule 108 petition to cancel the AAP/handwritten admission and correct the birth record. Evidence: DNA test, testimony, documents showing impossibility, etc. Outcome: entry naming the wrong father/surname is removed; child reverts to the mother’s surname (unless and until paternity with the bio father is lawfully established, or adoption happens).
Married mother gave birth; husband isn’t the bio father; family wants the biological father’s surname on record. → This runs into the presumption of legitimacy. Only the husband (or, in limited cases, his heirs) may file to impugn legitimacy—and within strict timeframes. If that succeeds, proceed to establish bio father’s paternity (paternity case or valid acknowledgment) and then RA 9255/adoption as applicable.
Teen or adult wants to change to a stepfather’s surname without adoption. → Rule 103 may be attempted, but courts usually won’t let Rule 103 replace adoption/filiation rules. You must show compelling, honest reasons (e.g., long, consistent use; genuine confusion/hardship; not to evade obligations). Adoption remains the sturdier route.
There’s no father on the birth certificate, but the child informally uses the stepfather’s surname in school. → School/yearbook usage doesn’t change legal identity. For passports, government IDs, inheritance, the PSA birth record controls. To align everything, pursue adoption (or, if the bio father will acknowledge, RA 9255—but only if he’s the bio father).

Documents & mechanics you’ll likely encounter

For RA 9255 (biological father only):
- Affidavit of Admission of Paternity (AAP) or private handwritten acknowledgment by the bio father (or court judgment establishing paternity).
- Affidavit to Use the Surname of the Father (AUSF):
  - 0–6 years: signed by the mother;
  - 7–17: child + mother;
  - 18+: child alone.
- Filed with the Local Civil Registrar (LCR) where the birth was recorded; forwarded to PSA.
For Step-Parent Adoption (RA 11642):
- File petition with NACC (Regional Office).
- Typical attachments: PSA birth certificate; marriage certificate of adopter & spouse; IDs; NBI/police clearances; medical certificate; proof of income; photos; written consents (child 10+, spouse, biological parents unless excused); social worker reports.
- Order of Adoption → PSA issues amended birth certificate; the child’s surname becomes the adopter’s surname; the original record is sealed (accessible only by law).
For Rule 108 (correction/cancellation):
- Verified petition in the proper trial court; join all interested parties; publication/notice; hearing(s).
- Show substantial evidence (often DNA).
- Court’s decision is sent to LCR/PSA to implement the correction.
For Rule 103 (change of name):
- Petition in the trial court of the petitioner’s residence; publication; hearing; clear, honest reasons; no circumvention of adoption/filiation.

Tip: Changing the surname in the civil registry is the change that matters. After PSA updates, cascade the new record to IDs, school, PhilSys, PhilHealth, GSIS/SSS, passport, bank, etc.

What won’t work (or often backfires)

Affidavit “from the mother and stepfather” to put his surname on the birth certificate without adoption → Invalid.
RA 9048 petition to change the surname as a “clerical error” → Not applicable to substantive surname swaps.
Using Rule 103 to give a stepfather’s surname just because the child uses it socially → Frequently denied where it sidesteps adoption/filiation rules.
DNA alone → Powerful evidence, but you still need the right proceeding (paternity case, Rule 108, etc.) to change the record.

Decision guide (follow the branch that fits)

Are the parents married to each other at the child’s birth?
- Yes → Child is legitimate → To remove the husband’s surname, first impugn legitimacy (narrow, time-barred & mainly the husband’s right). After that, establish paternity with the bio father (if desired) via RA 9255 or pursue adoption as appropriate.
- No → Child is illegitimate → Default mother’s surname. To use a father’s surname:
  - If bio father, use RA 9255 (+ AUSF).
  - If not bio father, the lawful path is adoption (RA 11642).
A wrong surname is already on the PSA record?
- Consider Rule 108 to cancel the wrong acknowledgment/entry and correct the record (often with DNA evidence).
- Then proceed—if desired—with RA 9255 (bio father) or adoption (stepfather).

FAQs

Can a mother alone decide to put the stepfather’s surname on the birth certificate? No. Without adoption, that would be invalid.

If the biological father refuses to sign, can the child still use his surname? Possibly—through a paternity case that judicially establishes filiation; afterwards, an AUSF may be processed under RA 9255.

We discovered the “father” who signed is not the bio dad. Can we just sign a new affidavit? No. You typically need a Rule 108 case to remove/cancel the invalid acknowledgment and correct the birth record.

Can we hyphenate (mother’s–father’s) surnames? Standards are strict, and practice varies. Civil registry law doesn’t freely allow custom formats. If you want something non-standard, expect to need a court order (and not all courts will allow it).

Does an annulment or declaration of nullity automatically change the child’s surname? No. Marital status changes don’t, by themselves, change a child’s civil registry entries.

What about travel while this is pending? Use the current PSA birth certificate. If a non-parent travels with the child, check DSWD travel clearance rules.

Practical checklist (by goal)

I’m a stepfather; I want my surname on my partner’s child.

Gather IDs, marriage certificate (if married to the mother), child’s PSA birth certificate.
Secure required consents (child 10+, spouse, bio parent unless excused).
File step-parent adoption with NACC → await Order of Adoption → update PSA and all IDs.

We need to remove a wrong father’s surname from the PSA record.

Consult counsel re: Rule 108 venue, parties, and evidence (consider DNA).
File petition → get court decision → LCR/PSA corrects record.
After correction, decide whether to proceed with RA 9255 (if the bio father will acknowledge) or adoption (if a non-bio father will assume parentage).

We want the bio father’s surname, but the mother was married when the child was born.

Discuss the viability of impugning legitimacy (who can file, deadlines).
If legitimacy is successfully impugned, establish paternity → RA 9255 or consider adoption.

Final notes

Philippine surname rules are status-driven (legitimate vs illegitimate) and record-driven (what’s on the PSA certificate).
Affidavits can’t defeat status rules. Use the correct proceeding: RA 9255 (bio father), adoption (non-bio father), Rule 108 (record cleanup), Rule 103 (limited name-change situations), and impugning legitimacy (narrow cases).
Because timelines and strategy can be case-dispositive—especially with legitimacy—talk to a family-law practitioner before filing anything.