Correspondence and forms relating to naturalization often include family or other details not noted on the issued certificate. After the Great War, if there was a problem, the file is likely to include a more detailed Security Department check of the applicant, and sometimes even their foreign country passports. The files are generally held by the relevent State Archives up to 1903. After 1904 they are held by the National Archives. The National Archives has applications and medical checks for refugees from the DP camps of Europe after WW2.
Some files are indexed by name, some are by ship, some are chronological.
There is no composite index. Although there was no general legal requirement to register a change of surname, certain government departments must be advised - passports, electoral rolls, pensions and taxation. Change of name is handled by State authorities, regulations vary from state to state. The type of information in these records is fairly inconsistent. Some files have a simple signed statement that the old name is not to be used in future.