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Tax ID Number

Also known as a TIN, a tax identification number, or tax ID number, is a nine-digit number the IRS uses to keep track of taxpayers. There are several types of TINs. A social security number itself is a TIN and is the most common type. There are also employee identification numbers (EIN), adoption identification numbers (AIN), and individual tax identification numbers (ITIN), and preparer’s tax identification numbers (PTIN).

By using different identification numbers, the IRS tracks individuals, businesses, estates, trusts, and individuals who may not qualify for a social security number, and those who prepare taxes.