Two common goals for children born out of wedlock are (1) to acquire legitimate status by legitimation (when legally possible), and (2) to carry the father’s surname or otherwise change the child’s surname in the civil registry. These are distinct paths that sometimes overlap:

Legitimation (Family Code) converts an illegitimate child into a legitimate child by operation of law if the parents later validly marry each other and were not disqualified to marry each other at the time of conception. Effects are retroactive to birth and include, among others, the right to bear the father’s surname.
Surname change for illegitimate children who cannot be legitimated is typically pursued administratively through an Affidavit to Use the Surname of the Father (AUSF) when the father acknowledges filiation (R.A. 9255 and its IRR), or judicially (Rule 103 / Rule 108) when administrative routes are unavailable or disputed.

Below is the complete framework, step-by-step procedures, and edge cases.

Part I — LEGITIMATION BY SUBSEQUENT MARRIAGE

Legal concept and requisites

Legitimation arises by operation of law when:

The child was conceived and born out of wedlock to parents who could have married each other (i.e., no legal impediment between them) at the time of conception; and
The parents subsequently contract a valid marriage with each other.

If, at conception, either parent was legally disqualified to marry the other (e.g., one was still married to someone else), legitimation is not available. Adoption or other remedies must be considered.

Effects of legitimation

Status: Child becomes legitimate, retroactive to birth.
Surname: Child assumes the father’s surname as a legitimate child; middle name convention follows the mother’s maiden surname.
Parental authority: Vests jointly in the parents in accordance with rules on legitimate children.
Succession and support: Child becomes a compulsory heir with legitime equal to that of legitimate children; full rights to support.
Civil registry: Birth record is annotated to reflect legitimation and the new name configuration.

Administrative route (typical, uncontested)

Most legitimation cases are handled administratively at the Local Civil Registry Office (LCRO) where the birth was registered (or PSA via the LCRO of the place where the marriage was recorded), by filing:

Affidavit of Legitimation by Subsequent Marriage, executed by the parents;
PSA Birth Certificate (child) and PSA Marriage Certificate (parents);
Valid IDs, fees, and any LCRO-prescribed forms.

Outcome: The LCRO forwards to PSA for annotation. Upon release, the PSA copy will state “Legitimated by subsequent marriage,” and the child’s name appears in the legitimate format (Given name + Mother’s maiden as middle name + Father’s surname).

Judicial route (contested or complex cases)

If legitimation is opposed, facts are disputed (e.g., filiation), or there are multiple substantial registry changes, file a Rule 108 petition (cancellation/correction of entries in the civil registry) in the RTC where the civil registry is located or where the petitioner resides. Make it adversarial (implead all interested parties, including the Civil Registrar and the State). Publication and hearing are required. The court order directs the LCRO/PSA to annotate the record.

Special notes & edge cases

Void or bigamous marriages: A subsequent marriage must be valid; a void marriage does not produce legitimation.
Conception timing: The absence of impediment is measured at conception; a later removal of impediment before marriage does not cure disqualification at conception.
Already legitimate: If the child was born after the valid marriage, the child is legitimate by birth—no legitimation needed.
Muslim Filipinos: The Code of Muslim Personal Laws may provide distinct rules; consult a Shari’a court or registrar when applicable.
Foreign elements: If birth or marriage occurred abroad, process a Report of Birth/Marriage then apply legitimation/annotation through PSA channels.

Part II — SURNAME OF AN ILLEGITIMATE CHILD (WHEN LEGITIMATION IS NOT AVAILABLE)

Baseline rule

An illegitimate child carries the mother’s surname by default. The child may use the father’s surname if the father acknowledges filiation in the manner allowed by law and the requirements of R.A. 9255 and its IRR are met.

Administrative route under R.A. 9255 (AUSF)

When applicable

Father’s acknowledgment appears on the child’s civil registry (e.g., on the birth record or through an Affidavit of Admission of Paternity or similar), or he executes/has executed a recognized instrument acknowledging the child.

Who applies / consents

Child below 7: Application is typically made by the mother, with the father’s acknowledgment forming the legal basis.
Child 7 to 17: Child’s written consent is required, in addition to the documentary basis for paternal acknowledgment.
Child 18+: Child applies personally.

Documents (typical)

Affidavit to Use the Surname of the Father (AUSF) on LCRO/PSA form;
PSA Birth Certificate (un-annotated copy);
AOP/acknowledgment or equivalent;
Valid IDs; fees; and any LCRO-specific requirements.

Outcome

LCRO forwards to PSA for annotation. The PSA birth certificate is reissued showing the father’s surname, the mother’s maiden surname as middle name remains customary practice for illegitimate children who use the father’s surname (subject to evolving civil registry guidance), and the original entry is annotated (not erased).

When the AUSF route is not available

The father refuses or cannot acknowledge; or acknowledgment is contested; or there are substantial corrections intertwined with the surname issue.
Proceed via court:
- Rule 108 (civil registry corrections) if the controversy centers on entries (filiation, acknowledgment).
- Rule 103 (change of name) if seeking a change of surname based on proper and reasonable cause (best interests of the child), even if entries are otherwise correct.

Part III — JUDICIAL PETITIONS INVOLVING A MINOR’S SURNAME

A. Rule 103 — Petition for Change of Name (including Surname)

When to use

Seeking to change the child’s surname (e.g., from father’s to mother’s or vice versa) for proper and reasonable cause, especially where no administrative path exists or where equities and best interests of the child must be judicially weighed.

Where filed

RTC of the petitioner’s residence.

Parties & standing

For a minor, through a parent with parental authority or a legal guardian. If parental authority is contested (e.g., parents estranged), expect the court to hear both and, if needed, appoint a guardian ad litem.

Procedure (high level)

Verified petition stating facts, grounds, and desired new name;
Publication once a week for three consecutive weeks in a newspaper of general circulation;
Hearing with the State (through the Solicitor General/City/Provincial Prosecutor) and interested parties given notice;
Court determines if there is proper and reasonable cause, guided by the best interests of the child (e.g., abandonment, harm/ridicule, long use of a different surname, confusion, safety, relationship with putative father, etc.);
If granted, the order directs LCRO/PSA to annotate the civil registry entries.

B. Rule 108 — Cancellation/Correction of Entries

When to use

To correct/annotate substantial civil status entries (e.g., filiation, legitimacy/illegitimacy, acknowledgment, effects of legitimation, or adoption) and to harmonize the record when multiple substantial changes are needed together.

Key points

Proceed adversarially: implead the Local Civil Registrar and all interested parties (parents, acknowledged father, etc.).
Publication and hearing required.
Result is a directive to annotate/correct entries at LCRO/PSA.

Part IV — HOW LEGITIMATION INTERACTS WITH SURNAME

If legitimation applies, the child becomes legitimate and automatically uses the father’s surname as a matter of status, not merely preference.
This is generally handled via administrative annotation after the parents’ valid marriage.
If there is opposition to the legitimation (e.g., claim of legal impediment at conception), a Rule 108 case resolves the dispute.
After legitimation, the name format typically follows the legitimate convention: Given name + Mother’s maiden as middle name + Father’s surname.

Part V — PRACTICAL PLAYBOOKS

A. If you qualify for legitimation

Confirm eligibility: No impediment at conception + subsequent valid marriage.
Gather: PSA Birth Cert (child), PSA Marriage Cert (parents), IDs.
Execute: Affidavit of Legitimation at LCRO; pay fees.
Wait for PSA annotation; then request updated PSA copies for school, passport, SSS, PhilHealth, etc.

B. If you don’t qualify for legitimation but want the father’s surname (R.A. 9255)

Ensure filiation is acknowledged (on birth record or by AOP/acknowledgment).
File AUSF at LCRO (check consent rules by age).
Secure annotated PSA birth certificate reflecting the father’s surname.

C. If administrative routes fail or are contested

Consult counsel and evaluate a Rule 103 (change of surname) and/or Rule 108 (civil registry corrections) petition.
Prepare for publication, notice, and a hearing focused on the child’s best interests.

D. Updating downstream records after annotation

With the PSA-annotated birth certificate, update PhilHealth/SSS/GSIS, school records, passport, and bank/insurance files. Maintain a document kit (original PSA copies + court order, if any).

Part VI — COMMON SCENARIOS & ANSWERS

1) We married after our child’s birth. Can we legitimate our child? Yes if neither of you was legally disqualified to marry the other at conception, and your marriage is valid. File the Affidavit of Legitimation at the LCRO for annotation.

2) The father won’t acknowledge the child. Can we still use his surname? Not administratively under R.A. 9255. Without acknowledgment, you must pursue judicial relief (e.g., establish filiation; then, surname).

3) We earlier used the father’s surname via AUSF, but now want to revert to the mother’s. Reversion is not an administrative clerical correction. Seek judicial change of surname (Rule 103), arguing the best interests of the child (e.g., abandonment, harm, confusion).

4) The father is deceased. Can the child use his surname? If there exists prior acknowledgment (in the record or document), AUSF/annotation may still proceed per LCRO rules. If none, consider judicial proceedings to establish filiation first.

5) Can I fix given/middle name issues at the same time?

Clerical errors or first-name changes may be addressed administratively (R.A. 9048, as amended by R.A. 10172).
Status/surname/filiation usually require Rule 103/108 or legitimation procedures, as applicable. You may consolidate related reliefs in court for coherence.

6) What middle name appears after legitimation or AUSF?

After legitimation (child now legitimate): standard convention is mother’s maiden surname as middle name; father’s surname as last name.
AUSF (illegitimate child using father’s surname): LCRO practice typically keeps the mother’s maiden surname as middle name; verify current registry guidance in your LCRO.

7) Our marriage turned out to be void; we already filed for legitimation. A void marriage produces no legitimation. Expect the LCRO to deny or the annotation to be challengeable. Consider adoption if you wish to confer legitimate status.

Part VII — CHECKLISTS & TEMPLATES

A. Affidavit of Legitimation (outline)

Identities of parents and child (name, DOB, registry details);
Statement of no impediment at conception;
Details of subsequent valid marriage;
Prayer for annotation of legitimation and corresponding name format;
Signatures, IDs, jurat.

B. AUSF (outline)

Child’s details and registry info;
Basis of acknowledgment (AOP/instrument/civil registry entry);
Age-specific consents (mother; child if 7–17);
Prayer to annotate the child’s surname to the father’s.

C. Rule 103 Petition (key allegations)

Child’s identity, residence, and current entries;
Grounds showing proper and reasonable cause and best interests;
Relief: authority to use the desired surname and directive to LCRO/PSA to annotate.

D. Rule 108 Petition (key allegations)

Specific entries to correct/cancel (e.g., filiation, legitimacy, acknowledgment);
Parties to be impleaded (LCRO, State, interested persons);
Prayer for an order directing annotation of changes.

Bottom line

Legitimation is the gold standard when available: if the parents could have married at conception and later validly marry, the child becomes legitimate (retroactively), acquires the father’s surname, and enjoys full rights of a legitimate child—usually via administrative annotation.
If legitimation is not available, an illegitimate child may use the father’s surname through R.A. 9255 (AUSF) when the father acknowledges filiation; otherwise, pursue court remedies.
Judicial petitions (Rule 103 and/or Rule 108) address surname changes, disputes, and substantial civil registry corrections, with the best interests of the child as the governing standard.
Always complete the downstream updates (PSA copies, school, passport, benefit agencies) after any annotation or court order to keep the child’s records consistent.