Section 453(1) in The Mumbai Municipal Corporation Act, 1888
(1)When the birth of any child has been registered and the name, if any by which it was registered, is altered or, if it was registered without a name, when a name is given to it, the parent or guardian of such child or other person procuring such name to be altered or given may, within twelve months next after the registration of the birth, deliver to the registrar, such certificate as hereinafter mentioned and the registrar, upon the receipt of that certificate shall without any erasure of the original entry, forthwith enter in the register book the name mentioned in the certificate as having been given to the child.