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's required information on all tax returns filed with the IRS.

All U.S. tax identification numbers (TINs) 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).1 Foreign tax identifying numbers (foreign TINs) aren't issued by the IRS, either. They're issued by the country in which the non-U.S. taxpayer pays taxes.

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. The agency assigns the applicant a special number when they're approved.

The TIN, which is also called a taxpayer identification number, is mandatory for anyone filing annual tax returns with the IRS. The agency uses it to track taxpayers. Filers must include the number on tax-related documents and when claiming benefits or services from the government.2

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 that 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 ensures 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 forms. Individuals are assigned TINs in the form of Social Security numbers (SSNs), whereas businesses such as 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).

TINs in Different Countries

Almost every country uses TINs for various reasons. Canada uses Social Insurance Numbers (SINs) for employment, tax, benefits, and credit purposes.3 The SIN is a nine-digit unique identifier that's 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.4

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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 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.5

A child must have an SSN before a parent can claim them as a dependent for income tax purposes so parents voluntarily apply for the number on behalf of their children.6 A child with an ITIN can also 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.

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 they're ineligible for SSNs. They're arranged in the same format as an SSN (XXX-XX-XXXX). The ITIN always begins with a 9.

The applicant must complete Form W-7 and submit documents supporting their resident status to get an individual tax ID number.7 Certain agencies including colleges, banks, and accounting firms often help applicants obtain their ITIN.

Employer Identification Number (EIN)

The IRS uses the Employer Identification Number (EIN) to identify corporations, trusts, and estates that must pay taxes. Just like SSNs, employer tax ID numbers are nine digits but they're read as XX-XXXXXXX. Those who qualify for EINs must apply for the number and use it to report their capital gains and income for taxation purposes. Applying for an EIN is free and businesses can obtain one immediately.8

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. The child must be a U.S. citizen or permanent resident to qualify and the adoption must be pending.9

Preparer Tax Identification Number (PTIN)

The IRS has required the listing of a PTIN on each tax return filed since Jan. 1, 2011. The use of the PTIN was optional before this time.10 Any preparer that charges to complete all or part of a tax return for another individual must have and use a PTIN.11

The Bottom Line

You can get a tax identification number by applying directly to the correct agency if you don't already have one. You can get a Social Security number through the Social Security Administration. You can usually obtain an Individual Taxpayer Identification number or a number for a business directly from the IRS.

Having a TIN is necessary for individuals to work in the United States and you can't file a tax return without one. Reach out to the IRS or United States Citizenship and Immigration Services if you're not a U.S. citizen, don't have a number, and you're unsure how to proceed. Numerous websites can help you as well, but be wary about using this option. Make sure they're not fraudsters before providing them with any of your personal information.