A federal tax id number is the number the IRS uses to identify a person or entity. For a person, your FTID is your Social security number. Businesses have an FTID which is usually a 2 digit number followed by a dash and 7 more digits. On W-2 forms it is usually referred to as a FED ID or Federal Identification number and is found in the box directly below the employer/lender/bank address box and next to the box with your SSN. nismax95 · 6 years ago.