Changing or correcting the surname on a birth certificate in the Philippines can be crucial for various reasons. The process varies based on whether the change is minor or substantial and whether the surname belongs to a legitimate or illegitimate child.

Correcting a Misspelled or Incorrect Last Name

If the surname is misspelled or incorrect, the process involves filing a petition for the correction of clerical error under Republic Act 9048. This can be done at the Local Civil Registry Office (LCR) where the birth certificate is registered. The requirements generally include:

Certified copy of the birth record.
Two or more supporting documents like baptismal certificate, voter’s affidavit, or employment record.
Filing fee of PHP 1,000.00【5†source】【7†source】.

Changing a Last Name

Changing a last name typically involves judicial proceedings unless it's a minor correction. Grounds for changing a surname include:

When the name is ridiculous or difficult to pronounce.
When the change is a result of legitimation.
When a person sincerely wants to adopt a Filipino name in good faith to erase signs of alienage【11†source】.

This process requires a court order from the Regional Trial Court, with requirements like NBI clearance, police clearance, and other supporting documents【11†source】.

Supplemental Report for Missing or Blank Last Names

If the surname is missing or blank, a supplemental report can be filed to "supply" the missing entry. This process is usually straightforward and involves:

Affidavit indicating the missing entry.
Two or more supporting documents like medical record, voter’s affidavit, or driver’s license.
Filing fee of approximately PHP 1,000 or less【8†source】.

For Illegitimate Children

For illegitimate children, if the father's surname is being added or changed, the process usually involves filing an Affidavit to Use the Surname of the Father with a Private Handwritten Instrument or an affidavit of acknowledgment from the father【6†source】【11†source】.

Seeking Legal Assistance

Given the complexity of legal proceedings, it's advisable to seek legal counsel or assistance when dealing with substantial changes to the surname on a birth certificate【9†source】.

Where to File

The petition can be filed at the civil registry office where the person resides or at the Philippine Consulate Office if the person resides abroad. The person or any authorized representative can file the petition【10†source】.

For more information, it's recommended to consult the Philippine Statistics Authority (PSA) or legal professionals specializing in family law【5†source】.