Definition

TIN (Taxpayer Identification Number)

Contributor(s): Corinne Bernstein

A Taxpayer Identification Number (TIN), in the United States, is a unique nine-digit number for identifying an individual, business or other entity in tax returns and additional documents filed with the Internal Revenue Service (IRS).

As a broad term, it includes Social Security numbers, Employer Identification Numbers, Individual Taxpayer Identification Numbers, Preparer Tax Identification Numbers and other identification numbers used in the administration of tax laws. The IRS assigns TINs, which are issued by either the IRS or Social Security Administration (SSA). Other countries have similar tax ID systems.

Why are TINs important?

A TIN must be provided on tax-related documents such as withholding forms, returns and statements. A number must also be furnished when claiming tax treaty benefits. (Under such treaties, residents of foreign countries may be taxed at a reduced rate or exempt from U.S. taxes.)

Uses of TINs

All materials submitted to the IRS to claim tax benefits or exclusions or pay taxes must include a TIN. Taxpayers filing annual tax returns need to include a TIN on the return, and employers reporting wages paid to employees have to provide the employees' TINs.

Financial institutions, healthcare organizations and others also use TINs for identification purposes. TINs are considered sensitive personally identifiable information (PII) because they are used to identify specific individuals and, when employed in combination with other personal information, can be used to access accounts, file insurance claims, apply for loans and open credit card accounts.

Keeping individual taxpayer ID numbers secure is essential; identity thieves who gain access to personal or business tax ID numbers can use the information to steal money or commit fraud, including tax fraud. Taxpayer ID numbers are vulnerable to theft from hackers and identity thieves or can fall into the wrong hands when parties with access to them don't adequately protect them. Data breaches of corporations and government agencies in recent years have given cybercriminals access to personnel and customer data, including TINs.

Types of Taxpayer Identification Numbers

There are five types of TINs in the U.S., including:

  • Social Security number (SSN). SSNs are issued to U.S. citizens and qualified immigrants. Most individuals employ their SSNs as their TINs. If an individual does not have a Social Security number, he or she must get approval for eligibility from the Social Security Administration and use Form SS-5 to get an SSN.
  • Employer Identification Numbers (EINs). Also called employer ID numbers, EINs are assigned by the IRS for corporations, partnerships, trusts and estates. Use Form SS-4 to apply for an EIN. However, sole proprietors with no employees can use either an SSN or an EIN number. Foreign entities that are corporations (but not individuals) must have a federal EIN to claim an exemption from withholding because of a tax treaty; these foreign entities must use Form SS-4.
  • Individual Taxpayer Identification Numbers (ITINs). ITINs are available to certain resident and nonresident immigrants, their spouses and dependents who are ineligible to get Social Security numbers. To get an ITIN, these individuals should file form W-7 with the IRS. In some cases, the IRS authorizes colleges, financial institutions and accounting firms to help applicants get ITINs.
  • Adoption Taxpayer Identification Number (ATIN). ATINs are issued by the IRS for a child who is in the process of being adopted by U.S. taxpayers. The number is usually temporary and will be replaced later by an SSN when the child is eligible. Form W-7A can be used to apply for an ATIN only if the child is a U.S. citizen or resident.
  • Preparer Taxpayer Identification Number (PTIN). PTINs must be included on all tax returns or claims for refunds that tax preparers fill out. The IRS offers a searchable online directory of preparers and their credentials. Volunteer preparers do not need a PTIN.

How do I find my TIN?

Because Taxpayer ID Number is an umbrella term, individuals, businesses and organizations don't apply directly for it. They need to apply for the appropriate identification number included under the TIN umbrella -- such as an SSN, EIN or ITIN.

Those doing business with a company can find its Tax ID Number on financial forms or by contacting the company or its representatives. The IRS has rules for releasing EINs. Since May 2019, "only individuals with taxpayer identification numbers -- either a Social Security number (SSN) or an individual taxpayer identification number (ITIN) -- may request an employer identification number," according to the IRS. "This new requirement … will provide greater security to the EIN process."

This was last updated in March 2020

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