[sagitariusrex]

For everybody who isn't acquainted with how Social Security Cards work in the US and how they came to be I highly recommend watching "Social Security Cards Explained" by CGP Grey https://www.youtube.com/watch?v=Erp8IAUouus

He also explains why US citizens don't have an Identity Card as opposed to many European countries.

[sitharus]

That’s quite crazy. Though here in NZ we don’t have a National ID number either, we have several different numbers for different purposes. Most places will work with a driver licence or passport number, but given there’s no need to register a change of name it gets a little tricky.

If you don’t have any of those you can get a statutory declaration of identity from a local court. You just have to swear you’re the person in front of a justice of the peace and provide a passport photo.