Employer Identification Number
United States · Companies
Paste or type the number — punctuation is optional.
Other identifiers
Europe
Asia and the Middle East
Oceania
What this check does — and what it cannot do
This tool checks the number's structure and its check digit, using the published algorithm for that document. A number that passes is well formed: it is arithmetically consistent and could have been issued.
It cannot tell you whether the number was actually issued, whether it is active, or who it belongs to. Only the issuing tax authority can confirm that, through its own lookup service. Treat a passing result as "worth submitting", never as proof of identity.
The US EIN has no check digit, so 83% of random numbers look plausible
An Employer Identification Number is nine digits with a two-digit prefix that encodes the issuing campus. There is no checksum. 83 of the 100 possible prefixes are in use, so a randomly generated number has an 83% chance of passing the only structural test that exists — and any typo in the remaining seven digits is completely undetectable.
How it works
- Checks the nine-digit format and validates the two-digit prefix against the assigned set.
- States plainly that no arithmetic check exists beyond the prefix.
- Distinguishes structural plausibility from the fact of issuance, which is not knowable offline.
format: XX-XXXXXXX (2-digit prefix, 7-digit serial) 83 of 100 two-digit prefixes are assigned no check digit anywhere in the number prefix valid → the only test available last 7 digits → completely unverifiable
Worked example
What the validation can and cannot establish.
- 83 assigned prefixes out of 100 possible
- a random 9-digit string has an 83% chance of a plausible prefix
- a mistyped digit in positions 3–9 always still passes
- a mistyped prefix digit fails only 17% of the time
The check is close to no check at all. It rejects the small minority of numbers with an unassigned prefix and accepts everything else, which makes it useful for catching a pasted phone number and useless for catching a typo.
Reading the result
- This is the same weakness as the US SSN and the direct opposite of the Canadian SIN, where Luhn catches every single-digit error. Three North American identifiers, three completely different levels of protection against the same mistake.
- The prefix originally encoded geography, but EINs have been issued centrally since 2001 and the prefix no longer indicates where a business is located. Validators that infer a state from it are describing a scheme that ended over two decades ago.
- Where correctness matters, the IRS TIN Matching service is the only authoritative check — it confirms that an EIN and a legal name correspond. No offline calculation can establish that a number was ever issued.
- Because typos are undetectable, double entry is the practical defence. Requiring the number twice catches transcription errors that no structural rule ever will.
Common questions
- Does a valid-looking EIN mean it is real?
- No, and less so than for most identifiers. Passing means the prefix is one of the 83 in use, which a random number achieves 83% of the time. Confirming a real EIN requires IRS TIN Matching.
- Can I tell which state an EIN came from?
- Not since 2001. Prefixes originally mapped to regional service centres, but issuance is now centralised and the prefix reflects the campus that processed the application rather than where the business operates.