text: i misplaced my tax id number and it has taken an act of congress to obtain it how do i find it irs is not coop   i can't vouch for this site (i've never used it), but they do seem to offer the service that you're looking for, so it's worth checking out.  i'm assuming that what you're looking for is the employer identification number (ein), also known as the federal tax identification number (tin). this site supposedly offers you the opportunity to look up 3 ein/tin numbers for free.  i hope it helps!