A Taxpayer Identification Number (TIN) is an identification number used by the Internal Revenue Service (IRS) in the administration of tax laws. It is issued either by the Social Security Administration (SSA) or by the IRS. A Social Security Number (SSN) is issued by the SSA, whereas all other TINs are issued by the IRS.
An Individual Taxpayer Identification Number (ITIN) is a tax processing number only available for certain nonresident and resident aliens, their spouses, and dependents who cannot get a Social Security Number (SSN). It is a 9-digit number, beginning with the number "9" and formatted like an SSN (000-00-0000).