I think the line you're referring to actually read "For social security and tax purposes - not for identification." As it was explained to me, it meant that the

I think the line you're referring to actually read "For social security and tax purposes - not for identification." As it was explained to me, it meant that the card itself was not a proof of identity, as opposed to something like a drivers license that had a picture and other identifying info. https://en.wikipedia.org/wiki/Identity_documents_in_the_United_States#Social_Security_card https://en.wikipedia.org/wiki/Identity_documents_in_the_Unit...