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What is a Tax Identification Number (TIN)?

What is a Tax Identification Number (TIN)?
Ines Zemelman, EA
06 November 2020

A taxpayer identification number (TIN) is a unique nine-digit number used to identify an individual, business, or other entity in tax returns and other documents filed with the Internal Revenue Service (IRS). 

Any government-provided number that can be used in the US as a unique identifier when interacting with the IRS is a TIN, though none of them are referred to exclusively as a Taxpayer Identification Number. A TIN may be:

  • a Social Security number (SSN), used by individuals who have (or had) the right to work in the United States;
  • an Individual Taxpayer Identification Number (ITIN), used by aliens who may or may not have the right to work in the US, such as aliens on temporary visas and non-resident aliens with US income, their spouses, and dependants;
  • an Employer Identification Number (EIN), also known as a FEIN (Federal Employer Identification Number), used by employers, sole proprietors, corporations, LLCs, partnerships, non-profit associations, trusts, estates of decedents, government agencies, certain individuals, and other business entities;
  • an Adoption Taxpayer Identification Number (ATIN), used as a temporary number for a child for whom the adopting parents cannot obtain an SSN;
  • a Preparer Tax Identification Number (PTIN), used by paid preparers of US tax returns. You must have a PTIN if you, for compensation, prepare all or substantially all of any federal tax return or claim for refund.

Why Do I Need a TIN?

A TIN must be provided on such tax created documents as returns, statements, and other. For example, a number must be furnished when you file your tax returns or claim treaty benefits.

Also, a TIN must be on a withholding certificate if the beneficial owner is claiming any of the following:

  • tax treaty benefits (other than for income from marketable securities);
  • exemption for effectively connected income;
  • exemption for certain annuities.

Often, expats encounter a request for a TIN when their bank or online marketplace asks to furnish Forms W-9/W-8 and provide their TIN (aka US tax ID). 

 How Do I Get a TIN?

A Social Security number (SSN) is issued by the SSA whereas all other TINs are issued by the IRS. For more information please see the Social Security Administration website and the Internal Revenue Service (IRS) website.


Ines Zemelman, EA
Founder of TFX