Retroactively putting the adoptive dad's name on the kid's birth certificate is common practice. That's how I sired Daring Daughter 3 years before I ever met her mom, at least I did it on paper, anyway... Thank you for doing that!
And I think I'm correct that her last name on her birth certificate is/was YOUR last name--?
Yes. She is Darling Daughter Void, as far as the law is concerned she has always been a Void, and we are genetically related.
I was amazed, pleased, and disturbed that history could be altered like that.