I always dig into "who has the paperwork" such as old W2 and paystubs, checking account and credit applications, medical coverage, any online account where you can see who is authorized or a beneficiary, even a mortgage or car loan. Anything that would be reported to a credit agency will have full SSN. I love it when someone separates, but isn't bothered digging out their part of the legal paperwork that was part of that "family."