What is a Col C-FeD ID Number?

[DMarkM1]

That sounds like an income form worksheet entry.  It could be a form W2 or a form 1099.  The FED ID number is the employer or payer's ID number typically found near the name and address of the payer on the form.  Once you know the form number (W2 or 1099) that is producing the error you should return to that entry topic to correct/enter the FED ID Number.