What supporting documents do I need for naturalization? We’ve put together a detailed guide about what supporting documents are needed for the citizenship application and interview. Related articles How long does it take for my naturalization application to be processed? What if I don't know all my past company addresses? How do I find a receipt number when my check was cashed but I never got a receipt notice? How do we verify a retired joint sponsor's income? Do I have to submit a police certificate if I lived in a foreign country for less than 12 months?