If you have a social security number, you can find it on your social security card (as pictured below). Some other places that you can find your SSN are on tax returns, pay statements, and bank statements. When completing USCIS forms and application, only use a valid social security number that was issued to you by the social security administration. If you do not have a valid SSN, leave the field blank. Using a false SSN will result in your application being rejected.