This document contains final regulations regarding an IRS truncated taxpayer identification number, or a TTIN. Where not prohibited by the Internal Revenue Code, applicable regulations, other guidance published in the Internal Revenue Bulletin, forms, or instructions, these regulations allow use of a TTIN in lieu of a taxpayer's social security number (SSN), IRS individual taxpayer identification number (ITIN), IRS adoption taxpayer identification number (ATIN), or employer identification number (EIN) on payee statements and certain other documents. The TTIN displays only the last four digits of a taxpayer identifying number; either asterisks (*) or Xs replace the first five digits of the identifying number. These regulations affect persons that furnish or receive payee statements and other documents that the Internal Revenue Code, regulations, or other published guidance requires to be furnished to another person to the extent that a TTIN may appear in lieu of the SSN, ITIN, ATIN, or EIN of the payee or document recipient.