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What Is a Tax Identification Number (TIN)? Definition, How to Get One

You may need a tax ID number when you file your taxes or talk to the IRS. Here’s what tax IDs are and how to get one.
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Written by Tina Orem
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When you file your tax return or need to talk to the IRS, you’ll likely have to provide a tax identification number, which is also called a TIN or tax ID number.

Here’s what a tax ID number is and how to apply for one.

What is a tax ID number?

A tax identification number, sometimes also called a "TIN number," is a unique nine-digit number that identifies you to the IRS. It's required on your tax return and requested in other official interactions. Tax ID numbers are assigned by either the IRS or the Social Security Administration

Internal Revenue Service. Taxpayer Identification Numbers (TIN). Accessed Dec 4, 2023.

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Types of TIN numbers

Social Security numbers are the most common tax ID numbers, but there are four other kinds that are popular, too. Skip down to learn more about each type of taxpayer identification number:

Individual taxpayer identification number (ITIN)

An individual taxpayer identification number, or ITIN, is a nine-digit tax ID number for nonresident and resident aliens, their spouses and their dependents who cannot get a Social Security number and are required to file taxes or have a tax ID number.

Internal Revenue Service. Taxpayer Identification Numbers (TIN). Accessed May 15, 2023.
The IRS issues the ITIN.

How to get an ITIN: To get an ITIN, fill out IRS Form W-7. You must prove your foreign/alien status and identity. Also, you must supply a federal income tax return to your Form W-7 (there are some exceptions; the instructions to the W-7 have the details). The form can either be mailed to the address listed on the Form W-7 instructions or it can be submitted in person at an IRS walk-in office. National and international organizations called “acceptance agents” also have IRS authorization to help people get ITINs. See the full list of acceptance agents here.


Employer identification number (EIN)

An employer identification number, or EIN, is a tax ID number for businesses that have employees; are corporations or partnerships; withhold taxes on income paid to nonresident aliens; have Keogh plans; are involved with certain types of organizations; or file employment, excise, or Alcohol, Tobacco and Firearms tax returns.

Internal Revenue Service. Do You Need an EIN?. Accessed May 15, 2023.
The principal business must be in the United States or a U.S. territory, and the person applying for the EIN (it must be an individual, not an entity) must already have a Social Security number, ITIN or other EIN. The IRS may require an estate or trust to get an EIN.

How to get an EIN: You can apply for this tax ID number online with the IRS. You can also fill out IRS Form SS-4 and fax it or mail it to the IRS. International applicants can call 1-267-941-1099 to get an EIN.


  • Your business may also need a separate state employer ID number.

  • Only one EIN can be issued to a responsible party per day.

  • If you lose track of your EIN, the IRS has a tool that can help you to locate it.

Adoption taxpayer identification number (ATIN)

An adoption taxpayer identification number, or ATIN, is a temporary, nine-digit tax ID number the IRS gives to people who are in the process of adopting a child. The IRS provides the number if the adopting parents cannot get a Social Security number for the child in time to file their tax return. The number identifies the child, not the parent, and is needed for the parent to claim the child as a dependent.

How to get an ATIN: To get an ATIN, file IRS Form W-7A. You’ll need to attach a copy of the placement documentation. The child must be legally placed in your home for adoption. If you’re adopting a child from another country, you can still get an ATIN, but there are more rules (see the details here).


  • You cannot claim the earned income tax credit with this tax ID number (you can only use a Social Security number to do that).

  • It takes four to eight weeks to get an ATIN once the IRS gets your Form W-7A, so ask for it well before your tax return is due.

    Internal Revenue Service. Adoption Taxpayer Identification Number. Accessed May 15, 2023.

  • Unless you notify the IRS that the adoption is still pending, the IRS will automatically deactivate an ATIN after two years.

Preparer tax identification number (PTIN)

A PTIN is a preparer tax identification number. The IRS requires anyone who prepares or assists in preparing federal tax returns for compensation to have a PTIN. Tax preparers must put their PTIN numbers on clients’ tax returns.

How to get a PTIN: Preparers can get PTINs from the IRS online in about 15 minutes; the application fee costs $19.75 in 2024

Internal Revenue Service. PTIN Top FAQ 4. Accessed Dec 4, 2023.
. Alternatively, they can fill out and mail IRS Form W-12. That method takes about four to six weeks.


  • Volunteer preparers don’t need PTINs.

  • You can look up the preparer on the IRS' PTIN directory.

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