1) Core concepts: legitimacy, illegitimacy, and filiation

Philippine family law classifies a child’s status primarily as legitimate, illegitimate, legitimated, or adopted. This status affects (among others) the child’s surname, parental authority, and inheritance rights.

Filiation is the legal relationship between a child and parent(s).
Legitimate children are generally those conceived or born during a valid marriage of the parents (subject to statutory presumptions and special rules).
Illegitimate children are those conceived and born outside a valid marriage, unless the law treats them as legitimate under specific provisions.
Legitimation is a legal mechanism that can convert certain illegitimate children into legitimate children by operation of law, once the statutory requirements are met.
A surname change in this context is usually not a “change of name” case in court; it is commonly the civil registry consequence of legitimation or of statutory authority (e.g., for an illegitimate child to use the father’s surname).

2) Legitimation under the Family Code: what it is and when it applies

A. Definition

Legitimation is the process by which a child who was conceived and born outside of wedlock becomes legitimate because the parents later validly marry, provided the parents had no legal impediment to marry each other at the time of the child’s conception.

This is governed by Articles 177 to 182 of the Family Code.

B. Requisites (all must be present)

A child may be legitimated only if:

The child was conceived and born outside a valid marriage of the parents;
At the time of conception, the parents were not disqualified by any impediment to marry each other; and
The parents later enter into a subsequent valid marriage.

Important boundary: If a child was conceived before the parents’ marriage but born during the parents’ valid marriage, that child is typically treated as legitimate already, and legitimation is generally unnecessary. Legitimation is aimed at children who were both conceived and born outside the parents’ marriage.

C. “No legal impediment at the time of conception” (the key limiter)

Legitimation is barred if, at conception, there existed an impediment that made the parents unable to validly marry each other, such as:

One or both were married to someone else at that time;
The relationship fell within prohibited degrees (incestuous or otherwise void by reason of relationship);
Either party lacked capacity to marry under the law then applicable (e.g., age, depending on the controlling law at the time of conception);
Other impediments that make marriage void.

Where this “no impediment” requirement is not met, a later marriage between the parents does not legitimate the child. In those cases, the child generally remains illegitimate, although other mechanisms (especially regarding surnames) may still be available.

D. Effect of legitimation

Once validly legitimated:

The child becomes legitimate, enjoying the same rights as a legitimate child (Family Code, Art. 179).
The effects retroact to the time of the child’s birth (Family Code, Art. 180), meaning the child is treated as legitimate from birth, subject to protections for third parties in appropriate contexts.
The child’s surname aligns with the rules for legitimate children (generally the father’s surname), and the child gains the legal incidents of legitimacy (notably in succession).

E. Who may challenge legitimation

Legitimation may be impugned only by those prejudiced in their rights, and within the statutory period (Family Code, Art. 181). This typically matters in inheritance situations or where legitimacy affects other legal entitlements.

3) How legitimation connects to surname change

A. Default naming framework

Legitimate / legitimated child: commonly recorded with the father’s surname; the mother’s maiden surname is typically the middle name.
Illegitimate child: by default uses the mother’s surname, and parental authority is generally with the mother (Family Code, Art. 176, as amended).

B. What changes when a child is legitimated

Legitimation changes the child’s civil status from illegitimate to legitimate. In practice, civil registry records are annotated to reflect legitimation, and the child’s surname is recorded/updated consistent with legitimacy (commonly the father’s surname).

This is usually done through civil registry annotation, not through a separate “surname change” lawsuit—unless there is a dispute or substantial correction issue.

4) Administrative recording: civil registry process to reflect legitimation and the child’s surname

Legitimation happens by operation of law when requisites exist, but to make it usable in daily life (schools, passports, benefits, inheritance documentation), it should be recorded/annotated in the child’s birth record.

A. Where to file

Usually with the Local Civil Registry Office (LCRO) where the child’s birth was registered. The LCRO then endorses the annotation to the PSA for issuance of an annotated PSA birth certificate.

B. Typical documentary requirements (expect variations by LCRO)

Commonly requested:

Child’s birth certificate (certified copy, and/or PSA copy)
Parents’ marriage certificate (PSA copy)
Affidavit of Legitimation (executed by the parents)
Proof of identity of parents (government-issued IDs)
If the father is not properly reflected/acknowledged in the birth record: documents establishing paternity/recognition (e.g., father’s acknowledgment instrument), as required by the registrar
Filing fees, and sometimes additional supporting documents depending on the case history

C. Affidavit of Legitimation: what it generally states

An affidavit typically includes:

Child’s full name as recorded, date and place of birth, registry details
Parents’ names and details
A statement that the child was conceived and born when the parents were not married to each other
A statement that at the time of conception, the parents had no legal impediment to marry each other
Details of the subsequent valid marriage (date/place)
A request to annotate the birth record to reflect legitimation and the child’s proper name/surname under legitimacy rules

D. What the LCRO/PSA typically does

The LCRO reviews the submissions and, when in order, annotates the birth record under “Remarks/Annotations” to show that the child has been legitimated by subsequent marriage, referencing the parents’ marriage details.
The LCRO forwards the documents to the PSA for annotation at the national level.
The PSA then issues an annotated birth certificate, which is the standard document used for most transactions.

E. Practical consequences after annotation

After receiving an annotated PSA birth certificate reflecting legitimation/surname:

Update the child’s name records in school, government benefits, insurance, bank accounts, travel documents, and other registries.
Maintain copies of the marriage certificate and legitimation papers; they may be repeatedly requested.

5) When legitimation is not available: other lawful ways a child’s surname may change

Not all cases qualify for legitimation. The Philippines has other mechanisms that can affect a child’s surname:

A. Illegitimate child using the father’s surname (RA 9255; Family Code Art. 176 as amended)

Even if a child remains illegitimate, the child may be allowed to use the father’s surname if the father has expressly recognized the child, typically through:

The record of birth (e.g., father recognized paternity in the birth registration); or
An admission/acknowledgment in a public document or a private handwritten instrument, consistent with the law and applicable civil registry rules.

In practice, civil registry implementation commonly involves filing an Affidavit to Use the Surname of the Father (AUSF) (or the registrar’s equivalent procedure), attaching proof of the father’s recognition.

Key legal point: Using the father’s surname under this route does not make the child legitimate. The child remains illegitimate, with the legal consequences of illegitimacy (notably in parental authority and inheritance rules), unless later legitimated or adopted.

B. Adoption

A decree of adoption typically results in:

The child taking the surname of the adoptive parent(s); and
Issuance of an amended birth record consistent with adoption laws and regulations.

Adoption is a distinct remedy with its own substantive and procedural requirements and should not be confused with legitimation.

C. Judicial change of surname (Rule 103) / correction of entries (Rule 108)

A person seeking to change a surname outside the typical statutory/registry routes may need court proceedings:

Rule 103 (Change of Name): used for changing one’s name/surname in court, requiring publication and hearing;
Rule 108 (Cancellation/Correction of Entries): used when the requested change is a substantial correction in civil registry entries (not merely clerical), often requiring an adversarial proceeding.

Practical caution: Courts scrutinize surname changes closely, especially if the change appears to alter or obscure civil status, filiation, or legitimacy issues. Courts generally do not allow surname changes to be used as a backdoor to rewrite filiation without proper legal basis.

D. Administrative corrections under RA 9048 / RA 10172 (limited scope)

These laws allow administrative correction of specified civil registry entries (e.g., certain clerical errors, first name changes, and limited items like day/month of birth or sex under specific circumstances). They generally do not cover substantive changes like legitimacy status or a full surname change arising from contested filiation issues.

6) Common scenarios and the correct pathway

Scenario 1: Parents were both single at conception; child born before marriage; parents later validly marry

Likely qualifies for legitimation.
File for civil registry annotation of legitimation; surname aligns with legitimacy.

Scenario 2: One parent was married to someone else at conception; parents later marry after annulment/nullity

Legitimation is generally barred because an impediment existed at conception.
The child remains illegitimate unless other remedies apply.
Surname options may be pursued under the mechanism for an illegitimate child to use the father’s surname (if recognition is present), or via adoption, as applicable.

Scenario 3: Father’s identity was not recorded; later father acknowledges; parents later marry

Two steps are commonly needed in practice:
1. Establish/record recognition/paternity in the civil registry in the manner required; then
2. Record legitimation (if requisites are satisfied).
If recognition/paternity is disputed, court proceedings may be necessary.

Scenario 4: Child already uses father’s surname as an illegitimate child (RA 9255 route), then parents later marry with no impediment at conception

Legitimation can still be recorded; the surname may remain the same in practice, but the status changes from illegitimate to legitimate, which matters legally.

Scenario 5: Child/parent wants to keep the mother’s surname even after legitimation

As a civil registry matter, legitimation aligns the child with legitimate-child naming conventions.
Keeping or changing away from that typically requires a separate legal basis and may involve judicial proceedings if it contradicts standard registry rules.

7) Legal consequences worth understanding before choosing a route

A. Legitimation changes civil status and legal rights

Legitimation affects more than the last name. It can change:

Inheritance rights (legitime and succession rules)
Parental authority framework
The child’s legal classification in official records

B. Using the father’s surname (while remaining illegitimate) is narrower

Using the father’s surname without legitimation:

Is primarily a naming privilege linked to the father’s recognition;
Does not automatically alter parental authority rules;
Does not convert the child into a legitimate child for succession purposes.

C. Civil registry entries are not just “labels”

A child’s “legitimate/illegitimate/legitimated” status in the civil registry is tied to legal presumptions and rights. Substantial changes—especially those affecting filiation—can become contentious and may require court involvement.

8) Practical checklist (for legitimation + surname update)

A. Before filing

Confirm that at the time of conception there was no impediment to the parents marrying each other.
Confirm the parents’ marriage is valid and properly registered.
Gather documents supporting the child’s recorded identity and the parents’ identities.

B. Typical submission package

PSA birth certificate of the child
PSA marriage certificate of the parents
Affidavit of Legitimation (parents)
IDs of parents
Additional recognition/paternity documents if needed by the registrar
Filing fees and LCRO forms

C. After annotation

Secure multiple certified copies of the annotated PSA birth certificate
Update records in schools, benefits, banks, and travel documents
Keep a file containing: birth certificate, marriage certificate, affidavits, and receipts

9) Summary: the map of options

Legitimation (Family Code Arts. 177–182)
- Requires subsequent valid marriage and no impediment at conception
- Child becomes legitimate (retroactive to birth)
- Civil registry is annotated; surname follows legitimacy rules
Illegitimate child uses father’s surname (RA 9255 / Art. 176 as amended)
- Requires father’s express recognition and compliance with civil registry procedure
- Child remains illegitimate; this is not legitimation
Adoption
- Separate legal process; surname changes by adoption decree and amended civil registry record
Judicial change/correction (Rule 103 / Rule 108)
- Used when changes are substantial, disputed, or outside administrative authority
- Requires court proceedings, publication, and hearing in appropriate cases