In the Philippines, the legal framework governing filiation and the rights of children is primarily dictated by the Family Code of the Philippines (Executive Order No. 209) and supplemented by Republic Act No. 9255. When a child is born to parents who are not validly married to each other, that child is classified as illegitimate.

The absence of a father’s name on a birth certificate creates a specific legal scenario regarding the child’s identity, support, and inheritance.

1. Legal Status and Filiation

An illegitimate child’s filiation is established by the fact of birth with respect to the mother. However, with respect to the father, filiation must be recognized. If the father’s name is missing from the birth certificate, the child is legally considered to have unestablished paternal filiation.

Maternal Side: The child automatically carries the mother’s surname and is under her sole parental authority.
Paternal Side: Until the father recognizes the child through a legal instrument, there is no "legal" father-child relationship, even if the biological reality is known.

2. The Right to Use a Surname

Under Article 176 of the Family Code, as amended by Republic Act No. 9255, the rules for surnames are as follows:

Default Rule: The child shall use the surname of the mother.
Exception: The child may use the father’s surname only if the father acknowledges the child through:

The Affidavit of Admission of Paternity (executed at the back of the Birth Certificate or as a separate document).
A Private Handwritten Instrument (a document written and signed by the father admitting paternity).

The "No Father" Scenario: If the father is not on the birth certificate and has not signed any admission of paternity, the child must use the mother’s surname. The Office of the Civil Registrar will not allow the use of the father's surname without these documents.

3. Parental Authority and Custody

Under Article 176, illegitimate children are under the sole parental authority of the mother.

Custody: The mother has the absolute right to custody. Even if the father later acknowledges the child, the mother retains primary rights unless she is proven unfit in a court of law.
The Father’s Role: A father whose name does not appear on the birth certificate has no legal right to demand custody or visitation (visitorial rights) until he formally recognizes the child or is declared the father by a court.

4. Right to Support

Every child has a right to support (food, shelter, medical care, education) from both parents. However, if the father is not on the birth certificate:

Condition Precedent: To demand legal support, paternity must first be proven.
Compulsory Recognition: The mother (or the child) may file a "Petition for Compulsory Recognition and Support" in court. They must present evidence such as DNA results, photos, letters, or testimonies to prove the biological link.
Once Proven: Once the court declares filiation, the father is legally obligated to provide support proportional to his means and the child's needs.

5. Successional Rights (Inheritance)

The Civil Code of the Philippines governs the inheritance rights of illegitimate children.

The 50% Rule: An illegitimate child is a compulsory heir but is entitled to only one-half (1/2) of the legitime (inheritance) of a legitimate child.
The Burden of Proof: If the father’s name is not on the birth certificate, the child cannot inherit from the father ab intestato (without a will) unless paternity was recognized during the father's lifetime or a court action for recognition was filed before the father's death (or under specific circumstances, after death).
Barred from the Father’s Family: Under the Iron Curtain Rule (Article 992 of the Civil Code), an illegitimate child has no right to inherit ab intestato from the legitimate relatives of their father or mother, nor shall such relatives inherit from the illegitimate child.

6. Correcting the Birth Certificate

If the father was omitted at birth but later wishes to be recognized, or if the mother wins a paternity suit, the birth certificate can be updated.

Administrative Process: If the father is willing, he can execute an Affidavit of Admission of Paternity (AAP) and an Affidavit to Use the Surname of the Father (AUSF) at the Local Civil Registry Office.
Judicial Process: If the father refuses recognition, a court order (Judgment of Paternity) is required to compel the Civil Registrar to annotate the birth certificate.

Summary Table of Rights

Category	Status with No Father on Record	Status After Legal Recognition
Surname	Mother's Surname only	Father's Surname (Optional)
Authority	Solely with the Mother	Solely with the Mother (usually)
Support	Not legally demandable	Legally demandable
Inheritance	None from the paternal side	1/2 of a legitimate child's share
Custody	Maternal	Maternal (Father may seek visitation)