changing surname

Can I change the surname of my son ? his father is willing to sign if needed . We're not married and he has a new family. and he has no given to my son needs for 7 months.

Your child can use the surname of the father by applying the provisions of RA 9255  (An Act Allowing Illegitimate Children to Use the Surname of Their Father, Amending for the Purpose Article 176 of Executive Order No. 209, Otherwise Known as the "Family Code of the Philippines").

The affidavit of acknowledgment executed by the father should be registered with the civil registry office where the birth of the child was registered. Since the surname being used is the surname of the mother, an Affidavit to Use the Surname of the Father (AUSF) should also be executed with the civil registry office where the birth is registered.

The mother or the father of the child or the child himself/herself, if of age, can file the application with the civil registry where the birth of the child was recorded. You need to bring with you the following documents:

1. Certified true copy of child’s birth certificate (most require NSO certificates)
2. Affidavit to Use the Surname of the Father
3. Affidavit of Acknowledgment executed by the Father (AAF)
4. Valid IDs of parents or the registrant if 18 years or older.

Note: In some cities/municipalities, the local civil registrar may require the personal appearance of the mother and the father to confirm their identities.

Processing time can vary but it will usually take a week.  Estimated cost Php1,000.00.

You can find here a sample format of the AUSF:

http://www.philippinelegalforms.com/2013/07/affidavit-to-use-surname-of-father.html

Or this format to use one affidavit for both AAF and AUSF to save on notarial fee:

http://bernepe.dfa.gov.ph/images/pdf/Affidavit%20of%20Acknowledgment%20of%20Paternity%20and%20Consent%20to%20use%20the%20surname%20of%20father.pdf