Why do I need to know my SSN?
Like your birth certificate, your SSN proves who you are. You’ll need to provide your 9-digit SSN to access government services and to apply for jobs, public benefits, housing, a driver license, health care, education programs, and financial aid.
I have a SSN, but I forgot it or never knew it. How do I find out what it is?
If you were assigned a SSN at some point in your life, but you don’t know it now, you need to request a replacement card. This is the only way to get your number because the Social Security Administration (SSA) does not give out Social Security numbers any other way. You can apply for a replacement card by mail or in person at a local SSA Field Office. For more information on getting a replacement card, see PG. 38 if you’re incarcerated, or PG. 39 if you’re out.
New or Replacement Social Security Number Card, Soc. Sec. Admin., http://www.ssa.gov/ssnumber/. ↑
How do I apply for a new or replacement Social Security card?, Soc. Sec. Admin., https://faq.ssa.gov/ics/support/kbanswer.asp?QuestionID=3755. ↑