We did eventually unravel her benefits. I don't think that there there is any cross checking of SSN's and who is using what. The IRS handled income tax returns and directs withholding. SSA administers payment of benefits. It's not like those data bases interact. When I was audited, the discrepancy came up because the other woman, in Fresno, filed under MY SSN claiming head of household with five children. Asking for proof of five children was a routine query. Had they not audited me, it could have gone on for years. When this woman was caught, she was given a TIN. No prosecution, nothing.