Social Security Number vs. International Tax Identification Number International fellows are required to have a Social Security Number (SSN) or, if you are not eligible for an SSN, an Individual Taxpayer Identification Number (ITIN). Information and directions to the closest Social Security Administration Office are found here. More information about how to apply and an application are also available. If you do not have an SSN or ITIN (note: By law, no individual can have both an ITIN and an SSN), information about applying for an ITIN is available from the Internal Revenue Service. It i...