A child must be registered at the Local Civil Registry office within 30 days after his birth. If the parents fail to do that, the child will not have a valid birth certificate and there will be no basis for the details of his birth.
If you register your child beyond the 30-day deadline, his birth certificate will be tagged “Delayed Registration” or “Late Registration”. Apart from the customary information you need to provide on the certificate such as the name, birth date and birthplace, and parents’ information, you also need to state why you failed to register the child’s birth on time.
Any person who has never had a birth certificate may file for the late registration of his birth, anytime. What is important is that you be able to secure an authenticated copy of the birth certificate, making sure that you are properly registered as a citizen of the Philippines.
If you want to know more about late registration of birth, here is a comprehensive article we found in the Citizen Services website.
MasterCitizen's Blog 
Mam wala po akung record sa nso,pro mag regestered po sana ako gusto kopo dito lng cagayan
Bakit wala kang record sa NSO (now PSA)? Hindi ka ba narehistro nung pinanganak ka, o hindi lang na endorse yung registration mo sa PSA? Pwede ka namang magpa rehistro sa Cagayan kung diyan ka na nakatira ngayon pero kailangan mo munang masiguro na wala ka pang registration noon (sa lugar kung saan ka pinanganak).