Which Social Security numbers are invalid? According to the SSA an invalid or impossible SSN is one that it never assigned. The SSN has never assigned any SSNs with the following first three digits:
- 000
- 666
- 900-999
Additionally, prior to June 25, 2011, the SSA has never assigned an SSN with the following first three digits:
- 000
- 666
- 772-999
The SSA has also never assigned an SSN with the second two digits of 00 or the last four digits of 0000.