Rules on Illegitimate Children's Surname

Public Document: Includes Affidavit of Admission of Paternity and related documents as enumerated in Memorandum Circular 04-12.
Private Handwritten Instrument: Handwritten and signed document by the father acknowledging paternity during his lifetime.
Affidavit to Use the Surname of the Father (AUSF): Document executed to allow the use of the father's surname; registrable.
Local Civil Registry Office (LCRO): City/municipal government office performing civil registration.
Philippine Foreign Service Post (PFSP): Embassies and Consulates General abroad, responsible for registration outside Philippines.
Civil Registrar General (CRG): Head of PSA, with authority over local civil registrars.
Guardian: Person lawfully charged to take care of a minor or incapable person, including substitute parental figures as per Family Code.
Certificate of Live Birth (COLB)/Report of Birth (ROB): Prescribed forms for birth registration in the Philippines and abroad respectively.

Father, mother, the person himself (if of legal age), or guardian may file Affidavit of Admission of Paternity and AUSF.
Father must personally file Private Handwritten Instrument; if deceased, mother, person himself (if of age) or guardian may file.

For births in the Philippines, registration occurs at the LCRO in the place of birth.
For births abroad, registration at PFSP of country of residence or nearest country with PFSP.
Documents executed abroad but pertaining to foreign births are registered at LCRO of place of execution.

Registration must be done within twenty (20) days from execution.
Delayed registration rules apply otherwise as per existing civil registration laws.

Examination for completeness by authorized registrar or consular officials.
Acceptance of COLB/ROB and attendant documents including Affidavits and PHI.
Recording of entries in the Register of Births and Register of Legal Instruments.
Annotation of birth records and distribution of copies to CRG, LCRO/PFSP, registrant, and filing office.
Issuance of certified copies and transcriptions with annotations as applicable.

Unacknowledged illegitimate children use the mother's surname by default.
Recognition without AUSF still uses mother's surname.
Children aged 0-6 use father's surname if AUSF executed by mother or guardian.
Children aged 7-17 use father's surname if they personally execute AUSF with guardian/mother attestation.
Upon reaching majority, the illegitimate child may use the father's surname by executing AUSF independently.

Specifies annotation protocols depending on presence or absence of AUSF and type of paternity admission document.
Details different scenarios for births not yet registered, previously registered under mother's surname but acknowledged or not, including use of AUSF.
Annotations reflect acknowledgment status and surname changes pursuant to R.A. 9255.