Individual Tax Identification Number (ITIN) An Individual Taxpayer Identification Number (ITIN) is a tax processing number the Internal Revenue Service (IRS) issues to an individual who needs to report income but is ineligible to obtain a Social Security number (SSN) from the Social Security Administration. This allows non-citizen borrowers who do not have a Social Security number to apply for a loan. Borrowers with ITIN cards can qualify for a mortgage as long as they meet the eligibility requirements.