add father to birth certificate in new york

hi im just wondering my now husband and i were not married when our son was born he has my maiden name and no father on his birth certificate,, how can i change his last name and add his father to the birth certificate? we now live in indiana, my son is almost 5 years old now,  thank you for all your answers and help

You can call your local child support enforcement agency for a paternity acknowledgement form and it can be done that way. Both parents need to sign this form and sign in front of a notary. Be sure to have photo id with you as well.

I'd be surprised if the child support agency is the way to go in Indiana. particularrly since you are now married I would assume there's no order in place.

It is likely you will need a DNA test to confirm paternity. Then check with the dept that handles birth certificates about the way to make a correction.