Tax Identification Number (TIN)

What Is a Tax Identification Number (TIN)?

A Tax Identification Number (TIN) is a nine-digit number used as a tracking number by the Internal Revenue Service (IRS). It is required information on all tax returns filed with the IRS. All U.S. tax identification numbers (TIN) or tax I.D. numbers are issued directly by the IRS except Social Security numbers (SSNs), which are issued by the Social Security Administration (SSA). Foreign tax identifying numbers (foreign TIN) are also not issued by the IRS; rather, they are issued by the country in which the non-U.S. taxpayer pays taxes.

1:31

Tax Identification Number (TIN)

Key Takeaways

  • Tax identification numbers are nine-digit tracking numbers used by the IRS following tax laws.
  • The IRS issues all U.S. tax I.D. numbers except for social security numbers, which are issued by the Social Security Administration.
  • Tax filers must include their tax identification number on tax-related documents and when claiming benefits.
  • TINs are also required when applying for credit and employment.
  • There are different types of tax identification numbers, such as the employer identification number, individual tax identification number, and adoption tax identification number.

Understanding the Tax Identification Number (TIN)

A tax identification number is a unique set of numbers that identifies individuals, corporations, and other entities such as nonprofit organizations (NPOs). Each person or entity must apply for a TIN. Once approved, the assigning agency assigns the applicant a special number.

The TIN, which is also called a taxpayer identification number, is mandatory for anyone filing annual tax returns with the IRS, which the agency uses to track taxpayers. Filers must include the number of tax-related documents and when claiming benefits or services from the government.

TINs are also required for other purposes:

  • For credit: Banks and other lenders require Social Security numbers on applications for credit. This information is then relayed to the credit bureaus to ensure the right person is filling out the application. The credit reporting agencies also use TINs—notably SSNs—to report and track an individual's credit history.
  • For employment: Employers require an SSN from anyone applying for employment. This is to ensure that the individual is authorized to work in the United States. Employers verify the numbers with the issuing agency.
  • For state agencies: Businesses also require state identification numbers for tax purposes in order to file with their state tax agencies. State taxing authorities issue the I.D. number directly to the filer.

Tax identification numbers or taxpayer-identification numbers come in several different forms. Individuals are assigned TINs in the form of Social Security numbers (SSNs), whereas businesses (e.g., corporations and partnerships) are assigned employer identification numbers (EINs). Other types of TINs include the Individual Taxpayer Identification Number (ITIN), the Adoption Taxpayer Identification Number (ATIN), and the Preparer Tax Identification Number (PTIN). More information about these types is noted below.

Special Considerations

Almost every country uses TINs for various reasons. For instance, Canada uses Social Insurance Numbers (SINs) for employment, tax, benefits, and credit purposes. Just like the SSN in the U.S., the SIN is a nine-digit unique identifier that is formatted as XXX-XXX-XXX.

Countries in the European Union also use TINs. They help government agencies identify taxpayers and allow entities to invest their money across the Union.

Types of Tax Identification Numbers (TIN)

Social Security Number (SSN)

The social security number (SSN) is the most common tax identification number. SSNs are issued to individuals—U.S. citizens, permanent residents, and certain temporary residents—by the Social Security Administration. These numbers are formatted as XXX-XX-XXXX.

The SSN is required to secure legal employment in the U.S. and to receive social security benefits and other government services. A child must have an SSN before a parent can claim them as a dependent for income tax purposes, which means parents voluntarily apply for the number on behalf of their children. A child with an ITIN can be claimed as a dependent. The SSA processes applications for free, but there are also fee-based services that offer to complete applications for new parents.

Your Social Security number is a unique identifier that can be misused by fraudsters, so make sure you only release it to those you are required to, including the IRS, employers, and lenders.

Individual Taxpayer Identification Number (ITIN)

The IRS issues the Individual Taxpayer Identification Number (ITIN) to certain nonresident and resident aliens, their spouses, and their dependents when ineligible for SSNs. Arranged in the same format as an SSN (XXX-XX-XXXX), the ITIN begins with a 9. To get an individual tax id number, the applicant must complete Form W-7 and submit documents supporting his or her resident status. Certain agencies—including colleges, banks, and accounting firms—often help applicants obtain their ITIN.

Employer Identification Number (EIN)

The IRS uses the Employee Identification Number (EIN) to identify corporations, trusts, and estates that must pay taxes. Just like SSNs, employer tax ID numbers are also nine digits long, but they are read as XX-XXXXXXX. Those who qualify for an EIN must apply for the number and use it to report their income for taxation purposes. Applying for an EIN is free, and businesses can obtain one immediately. 

Adoption Tax Identification Number (ATIN)

The ATIN only applies to domestic adoptions when the adoptive parents cannot obtain the child's SSN to complete their tax returns promptly. To qualify, the child must be a U.S. citizen or permanent resident and the adoption must be pending.

Preparer Tax Identification Number (PTIN)

As of Jan. 1, 2011, the IRS required the listing of a PTIN on each return filed. Before this date, the use of the PTIN was optional. Any preparer that charges to complete all or part of the tax return for another individual must have and use the PTIN.

Tax Identification Number (TIN) FAQs

How can I get a TIN?

You can get a tax identification number by applying directly to the correct agency. For instance, you can get a Social Security number through the Social Security Administration. If you need an Individual Taxpayer Identification number or one for a business, you may be able to obtain one directly from the Internal Revenue Service.

How do I know if I need a TIN?

You need a TIN if you are authorized to work in the United States or if you plan to file taxes with the IRS. You'll also need a TIN if you want to take advantage of benefits or services offered by the government. If you run a business or other organization, you'll also need a TIN to run your day-to-day operations and to report your taxes.

How can I find my TIN online?

The agency that issues your TIN provides you with an official document with your unique identifier. Because it is a sensitive piece of information, you can't go online to retrieve it. If you can't remember or lose your documents, you should contact the issuing agency, such as the SSA, to get your TIN again.

Is a TIN the same as a tax I.D.?

A TIN is the same as a tax I.D. as it stands for tax identification number or taxpayer-identification number.

Is a TIN the same as a Social Security number?

A Social Security number is an example of a TIN. It allows you to seek employment in the United States, to obtain credit with banks and other lenders, and you can file your annual tax returns with the IRS using your SSN.

Article Sources

Investopedia requires writers to use primary sources to support their work. These include white papers, government data, original reporting, and interviews with industry experts. We also reference original research from other reputable publishers where appropriate. You can learn more about the standards we follow in producing accurate, unbiased content in our editorial policy.
  1. Internal Revenue Service. "Taxpayer Identification Numbers (TIN)." Accessed Feb. 23, 2021.

  2. Internal Revenue Service. "U.S. Taxpayer Identification Number Requirement." Accessed Feb. 23, 2021.

  3. Government of Canada. "Social Insurance Number - Overview." Accessed Feb. 23, 2021.

  4. European Commission. "TIN - Taxpayer Identification Number." Accessed Feb. 23, 2021.

  5. Social Security Administration. "Social Security Number and Card." Accessed Nov. 30, 2019.

  6. Internal Revenue Service. "Qualifying Child Rules." Accessed Nov. 30, 2019.

  7. Internal Revenue Service. "Individual Taxpayer Identification Number." Accessed Nov. 30, 2019.

  8. Internal Revenue Service. "Employer ID Numbers." Accessed Nov. 30, 2019.

  9. Internal Revenue Service. "Adoption Taxpayer Identification Number." Accessed Nov. 30, 2019.

  10. Internal Revenue Service. "What Every Tax Return Preparer Needs to Know about Applying for a PTIN." Accessed Nov. 30, 2019.

  11. Internal Revenue Service. "PTIN Requirements for Tax Return Preparers." Accessed Nov. 30, 2019.