Documentation
In general, all pages of the census declaration in which a box has been marked or completed must be identified with the NIF (if available) and the name and surname or business name of the holder of the declaration.
In the event that the census declaration is signed by a person other than the person listed as the declarant, a photocopy of the document proving his or her identity must be attached. If the interested party appears before the Tax Authority, it will not be necessary to provide a photocopy of the DNI , provided that he/she authorizes the bodies of the AEAT to verify his/her identity data.