How to verify SS #

[Max T.]

So I have a cosigner's SS number from his paper application. I also had him complete a background check through mysmartmove. The smartmove report indicates that I should verify his SS # because it may be invalid. 

What is the best/fastest/cheapest way to do this?

[Mags S.]

if a new immigrant could not produce a ss card, I'd be leary