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EIN

General

US Employer Identification Number

A 9-digit number issued by the IRS to identify a business entity for tax purposes, functioning as the corporate equivalent of an individual's SSN.

Definition

An Employer Identification Number (EIN), also called a Federal Tax Identification Number, is a 9-digit number issued by the US Internal Revenue Service (IRS) to identify a business entity for tax administration purposes. It functions as the corporate equivalent of an individual's Social Security Number (SSN) — required for filing business tax returns, opening business bank accounts, hiring employees, and applying for business licenses.

EINs are issued to corporations, partnerships, LLCs, sole proprietorships that hire employees, non-profits, trusts, and estates. The number is formatted as XX-XXXXXXX: a 2-digit prefix followed by a 7-digit sequence number.

Formula

An EIN has no checksum digit, but it does have a structural validation rule based on its 2-digit prefix. The IRS maintains a published list of valid prefixes corresponding to the campuses and processing centers that have issued EINs over time (for example, prefixes like 01–06, 10–13, 16, 20–27, 30–48, 50–99 fall within ranges the IRS has actively used, while certain values have never been assigned). A number is considered structurally valid only if:

  1. It has exactly 9 digits, formatted as XX-XXXXXXX.
  2. The 2-digit prefix falls within a range the IRS has issued.
  3. The remaining 7 digits are not all zeros.

As with an SSN, this checks plausibility of format — only the IRS can confirm that a specific EIN is actually registered to a real, active business.

Worked Example

A structurally valid but entirely fictional example: 12-3456789, formatted with the 2-digit prefix separated from the 7-digit sequence number by a hyphen.

Key Things to Know

  • XX-XXXXXXX format: always 9 digits total, split 2-and-7 with a hyphen — different from the 3-2-4 grouping of an SSN.
  • Prefix indicates issuing campus, not geography: since IRS EIN issuance consolidated in 2001, the prefix no longer maps to a specific US state.
  • No checksum digit: like SSNs, EINs rely on structural and prefix-range validation rather than a mathematical check digit; use the EIN Validator or EIN Formatter to check formatting.
  • Required for most businesses: any entity with employees, or organized as a corporation or partnership, must obtain an EIN even if a sole proprietor could otherwise use their SSN.
  • Different from a DUNS Number: an EIN is a federal tax ID; a DUNS Number is a Dun & Bradstreet business credit identifier — many businesses hold both.
  • Public in some contexts: unlike SSNs, EINs for public companies and non-profits are often disclosed on tax filings (like Form 990) and are not treated as confidential in the same way.

Related Terms

SSNUS Social Security NumberDUNS NumberData Universal Numbering System Number

Frequently Asked Questions

An EIN is a 9-digit number formatted as XX-XXXXXXX — a 2-digit prefix followed by a 7-digit sequence number, separated by a single hyphen. You can check whether a number follows this structure and uses a valid prefix with the [EIN Validator](/validators/ein-validator/).
Yes, historically the 2-digit prefix indicated which IRS campus or service center issued the EIN, and the IRS publishes the valid list of prefixes currently in use. Since the IRS consolidated EIN issuance to a single system in 2001, the prefix no longer maps to a specific geographic location, but it must still fall within the set of prefixes the IRS has ever assigned.
Sole proprietors and single-member LLCs can obtain an EIN even though they could use their [SSN](/glossary/ssn/) for the same tax filings, often to avoid disclosing a personal SSN to clients or vendors. Any business that hires employees, operates as a corporation or partnership, or files certain tax returns is required to have an EIN regardless of individual preference.
Yes, an EIN is a federal identifier issued by the IRS and used consistently across all US states for federal tax purposes, unlike state-level business registration numbers which vary by state. A business may still need separate state tax IDs in addition to its single federal EIN.
An EIN is a US federal tax identifier issued by the IRS, while a [DUNS Number](/glossary/duns/) is a business identifier issued by the private company Dun & Bradstreet and used internationally for credit reporting and federal contracting. A single business commonly holds both, for different purposes.