Taxpayer identification number
Taxpayer identification number (TIN) means the identifying number required on tax returns and other documents submitted to the Internal Revenue Service; that is, an individual's social security number (SSN) or an employer identification number (EIN). A SSN is composed of nine digits separated by two hyphens, for example, 123-45-6789. An EIN is composed of nine digits separated by one hyphen, for example, 12-3456789. The hyphens are an essential part of the numbers.