I can't talk for England but in Scotland I have come across children as early as 1860's listed as Adopted. One family had 4 adopted children they were in the census with their birth surnames , married with their adopted names and died as either . Found another one yesterday : Marriage 1919 ' Ann Stewart adopted the name Bankier since child hood' blah blah blah . In 1891 Census she was aged one year old living with a Bankier family . Maybe her parents were good friends with this particular Bankier family they certainly weren't related . It does make research confusing though , especially the family I found with 4 adopted children in 1861 . You don't say when these adoptions might have taken place but my advice is buy ALL the certificates . Angela Down Under