All numbers issued by the IRS are "Taxpayer Identification Numbers." The important thing to remember is whatever number one uses, it can ONLY be treated as "Taxpayer Identification Number. " IRS puts "SSN" on its forms so as to encurage most Americans to falsely conclude that they MUST participate in what actually amounts to a municipal donation program for the District of Columbia. The forms request: "Your Social Security Number". The Social Security Number is not "Your" number. It is the property of the US government. It says so in their regulations:
"Social Security number cards are the property of SSA and must be returned upon request."
Again, all numbers issued by the IRS are Taxpayer Identification Numbers:
§ 301.6109-1 Identifying numbers.
(a) In general—(1) Taxpayer identifying numbers—(i) Principal types. There are several types of taxpayer identifying numbers that include the following: social security numbers, Internal Revenue Service (IRS) individual taxpayer identification numbers, IRS adoption taxpayer identification numbers, and employer identification numbers. Social security numbers take the form 000–00–0000. IRS individual taxpayer identification numbers and IRS adoption taxpayer identification numbers also take the form 000–00–0000 but include a specific number or numbers designated by the IRS. Employer identification numbers take the form 00–0000000.
§ 301.7701-11 Social security number.
For purposes of this chapter, the term social security number means the
taxpayer identifying number of an individual or estate which is assigned pursuant to section 6011(b) or corresponding provisions of prior law, or pursuant to section 6109, and in which nine digits are separated by hyphens as follows: 000-00-0000. Such term does not include a number with a letter as a suffix which is used to identify an auxiliary beneficiary under the social security program. The terms “account number” and “social security number” refer to the same number.
26 CR Sec. 301.6109-1(d)(3)
(3) IRS individual taxpayer identification number—(i) Definition. The term
IRS individual taxpayer identification number means a taxpayer identifying number issued to an alien individual by the Internal Revenue Service, upon application, for use in connection with filing requirements under this title. The term IRS individual taxpayer identification number does not refer to a social security number or an account number for use in employment for wages. For purposes of this section, the term alien individual means an individual who is not a citizen or national of the United States.
http://famguardian.org/Subjects/Taxe...esponsible.htm
There is also a pamphlet at family guardian (sedm.org) entitled "Who are Taxpayers and who needs a Taxpayer Identification Number."