Taxpayer Identification Number

A Taxpayer Identification Number (TIN) is an identifying number used for tax purposes in the United States. It is also known as a Tax Identification Number or Federal Taxpayer Identification Number. A TIN may be assigned by the Social Security Administration or by the Internal Revenue Service (IRS).

Section 6109(a) of the Internal Revenue Code provides (in part) that "When required by regulations prescribed by the Secretary [of the Treasury or his delegate] [ . . . ] Any person required under the authority of this title [i.e., under the Internal Revenue Code] to make a return, statement, or other document shall include in such return, statement or other document such identifying number as may be prescribed for securing proper identification of such person."

Internal Revenue Code section 6109(d) provides: “The social security account number issued to an individual for purposes of section 205(c)(2)(A) of the Social Security Act [codified as 42 U.S.C. § 405(c)(2)(A)] shall, except as shall otherwise be specified under regulations of the Secretary [of the Treasury or his delegate], be used as the identifying number for such individual for purposes of this title [the Internal Revenue Code, title 26 of the United States Code].”