If you lose your Social Security number card, you cannot find the number or apply for a replacement card online, reports the Social Security Administration. Instead, obtain the application form for a new card online, and mail or take it in person to a local Social Security office.
To find the information and form necessary to replace a lost Social Security number card, go to the main page of the Social Security website, select Numbers & Cards in the toolbar at the top of the page, and click on New or Replacement Social Security Number Card, as the site directs. Access a form with instructions by clicking on Fill Out & Print an Application. Fill out the form online and then print it out, or print out the form first and fill it out by pen.
Applicants for replacement Social Security number cards must provide two separate documents to prove citizenship and identity, states the Social Security Administration. The documents must be originals or certified copies and not photocopies or notarized copies. Submit a U.S. birth certificate, U.S. hospital record of birth, U.S. passport, Consular Report of Birth Abroad or Certificate of Naturalization to prove citizenship. Use a U.S. driver's license, non-driver state ID, U.S. passport or a combination of other official photo ID documents to prove identity. If you already have proven citizenship, you only need to provide proof of identity.