Free Guide to IRS Number Types and Uses

What IRS Numbers Are and Why They Matter

The Internal Revenue Service (IRS) uses several different identification numbers to track individuals, businesses, and organizations for tax purposes. Each number serves a specific function in the tax system. Understanding which number applies to your situation is the foundation of dealing with the IRS effectively.

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An IRS number is a unique identifier that the federal government assigns to help organize tax records. Think of it like a filing system—just as a library uses call numbers to locate books, the IRS uses identification numbers to organize millions of tax records. These numbers appear on tax forms, correspondence from the IRS, and official documents.

The IRS currently uses several main types of identification numbers. The most common is the Social Security Number (SSN), which is used for individual taxpayers and workers. Another frequently used number is the Employer Identification Number (EIN), also called a Federal Employer Identification Number (FEIN), which identifies businesses and organizations. There is also the Individual Taxpayer Identification Number (ITIN), which serves people who cannot obtain an SSN. Tax-exempt organizations use an EIN as well, but for different purposes than regular businesses.

According to IRS data from 2023, approximately 150 million individual tax returns are filed annually in the United States. Each return uses at least one of these identification numbers. Knowing which number applies to you prevents confusion when filing taxes, opening business accounts, or corresponding with the IRS.

Practical takeaway: Determine which IRS number type applies to your situation—individual taxpayer, self-employed person, business owner, or organization—so you understand which identifier you need and how to use it correctly.

Social Security Numbers (SSNs) and Individual Taxpayers

A Social Security Number (SSN) is a nine-digit identifier issued by the Social Security Administration (not the IRS) to U.S. citizens, permanent residents, and certain temporary residents. The IRS uses SSNs as the primary identification method for individual income tax filing, wage reporting, and tax withholding.

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The SSN format consists of three parts: the area number (first three digits), the group number (middle two digits), and the serial number (last four digits). For example, a number might appear as XXX-XX-XXXX. The IRS cross-references SSNs with employment records, investment income reports, and other financial documents to verify tax filings.

When you earn income as an employee, your employer uses your SSN to report your wages to the IRS on a Form W-2. Financial institutions report interest and dividend income using your SSN on Forms 1099. Even if you file taxes electronically, your SSN remains the core identifier throughout the process. The IRS matches income reported on these forms to your individual tax return to check for discrepancies.

The Social Security Administration has issued over 450 million SSNs since the program began in 1936. Currently, there are approximately 330 million valid SSNs in circulation. If you lose your SSN or it is compromised, you can request a replacement from the Social Security Administration, though this requires documentation of identity.

SSNs also serve purposes beyond the IRS. Banks, credit card companies, and other financial institutions use SSNs to track credit history. Employers use them for employment verification. Schools and loan servicers use them for student loan tracking. The key point for tax purposes is that your SSN connects all your tax-related income reports to your individual tax return.

Practical takeaway: Keep your SSN secure and verify it matches all your income documents (W-2s, 1099s) before filing your tax return. If the number shown on these forms differs from your actual SSN, contact your employer or the institution that issued the form to correct it.

Employer Identification Numbers (EINs) for Businesses and Organizations

An Employer Identification Number (EIN), officially called a Federal Employer Identification Number (FEIN), is a nine-digit code the IRS assigns to identify businesses, partnerships, corporations, nonprofits, trusts, and other organizations. Unlike an SSN, which identifies a person, an EIN identifies a business entity itself.

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The EIN format also uses nine digits but is formatted differently than an SSN: XX-XXXXXXX. For instance, an EIN might appear as 12-3456789. The first two digits indicate the state where the business was formed or the IRS processing center that issued the number. The remaining seven digits are unique to that specific entity.

Businesses use EINs for several critical functions. When a business has employees, it must use its EIN to report payroll taxes and file employment tax returns like the Form 941 (quarterly payroll tax return). Self-employed individuals who have no employees may use either their SSN or an EIN, though many choose to obtain an EIN to separate personal and business finances. Partnerships must have an EIN to file partnership tax returns. Corporations must have an EIN regardless of whether they have employees.

According to IRS records, approximately 30 million active EINs exist in the United States. The number of new EIN registrations varies yearly but typically ranges from 1 to 3 million new EINs issued annually. This variation depends on economic conditions and the number of new business startups.

Banks and financial institutions require an EIN to open a business bank account. Vendors and suppliers often request an EIN before extending credit to a business. Government agencies use EINs when issuing business licenses or contracts. The IRS uses the EIN to track all tax filings, employment records, and compliance activities related to that business.

Practical takeaway: If you operate a business, obtain an EIN through the IRS website or by mail. Even if you are self-employed with no employees, using an EIN helps maintain clear separation between personal and business finances, which simplifies tax preparation and record-keeping.

Individual Taxpayer Identification Numbers (ITINs) for Non-Citizens

An Individual Taxpayer Identification Number (ITIN) is a nine-digit tax identification number issued by the IRS to individuals who are required to file a U.S. tax return but cannot obtain a Social Security Number. The ITIN was created in 1996 to facilitate tax compliance among non-residents and individuals ineligible for SSNs.

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The ITIN format resembles an SSN in structure (XXX-XX-XXXX) but uses a different number range. All ITINs begin with the number 9, and the middle two digits fall within specific ranges (50–65, 70–88, or 90–92) that distinguish them from SSNs. This format allows the IRS to quickly identify that a number is an ITIN rather than an SSN.

The IRS issued its first ITIN in 1996, and by 2023, over 16 million ITINs had been issued. Current estimates suggest approximately 11 to 12 million valid ITINs are in use. The majority of ITIN holders are foreign nationals who earn U.S. income, such as visa holders, students, or temporary workers who do not qualify for an SSN.

People who may obtain an ITIN include nonresident aliens with U.S. source income (such as rental property income or investment returns), visa holders (including H-1B, L-1, or O-1 visa holders) who work in the United States, students on F-1 or J-1 visas who have U.S. income, individuals filing joint tax returns with U.S. citizen spouses, and dependents of U.S. citizens or permanent residents. A person may have both an SSN and an ITIN, though only one is used for tax filing purposes.

The ITIN can be used to file individual income tax returns, claim refunds, establish work authorization in some contexts, and open certain types of financial accounts. However, an ITIN does not provide work authorization or change immigration status. It is strictly a tax identification number.

Practical takeaway: If you are a non-U.S. citizen earning U.S. income or filing a U.S. tax return, determine whether you should apply for an ITIN through the IRS. This involves submitting Form W-7 with documentation verifying your identity and foreign status.

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