Same issue here with TriNet as the PEO. They sent a letter explaining that (though I'm only going to get the single W-2 with one FEIN) they consider my 'real' companies the employers so they followed the advice to ignore overpaying the SocSec and that I have to file form 843 to get the money from the gov't not from them. They also sent along a letter to the gov't to put in with the form explaining why it's not on TriNet to give the money back.
