In Scotland, anybody is allowed to change his or her name legally at any time, provided that this is not an attempt to defraud. Changing your name by Deed Poll is relevant in English law only.
Statutory Declarations
Although you can change your name informally in Scotland, some agencies, such as Banks and the Passport Authority may ask for proof to show the connection between your new name and your original name. A Statutory Declaration is a signed document declaring that, from a stated date, an individual has been using the new name. It must be signed in the presence of a Notary Public or local Registrar. A parent can sign a declaration on behalf of a child under 16 years of age.