US EIN format validator
Check a US EIN before it goes on a W-9 or vendor record: 12-3456789 has nine digits, the hyphen after the prefix and the prefix 12, which the IRS Andover campus assigns. Prefixes the IRS never issued are flagged. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Ein
- 12-3456789
- Ein
- 123456789
- Formatted
- 12-3456789
- Prefix
- 12
- Serial
- 3456789
A United States Employer Identification Number (EIN) is the nine-digit federal tax ID the IRS assigns to businesses, estates, trusts, nonprofits, and other entities. It is written as XX-XXXXXXX: a two-digit prefix that historically identifies the IRS campus or channel that issued the number, followed by a seven-digit serial body. Before you store an EIN on a W-9, payroll master file, vendor record, or KYC form, a format and prefix check catches transposed digits, missing hyphens, and prefixes that the IRS never issued. This capability validates the nine-digit layout (with or without the standard hyphen), looks up the prefix against the published IRS campus and online-assignment table, returns whether the number is format-valid with a known prefix, and names the assigning campus or campuses when the prefix is shared.
What a US EIN is and how IRS campus prefixes work
An Employer Identification Number is a nine-digit identifier issued free by the Internal Revenue Service for tax filing, banking, employment, and entity registration. The printed form is almost always XX-XXXXXXX: two prefix digits, a hyphen, and seven serial digits. Before centralization in the early 2000s the prefix often reflected geography; today the first two digits mainly show which IRS campus assigned the number or whether the application went through the online system or the Small Business Administration.
The IRS publishes a table of valid prefixes for campuses such as Andover, Atlanta, Austin, Brookhaven, Cincinnati, Fresno, Kansas City, Memphis, Ogden, and Philadelphia, plus Internet and SBA rows. A few prefixes appear on more than one row—for example some codes are listed under both Internet and Philadelphia—so a careful validator returns every matching campus rather than inventing a single exclusive owner.
Prefixes that never appear on that table (for example 00 or 07) mean the nine-digit string cannot be a correctly assigned modern EIN even if it has the right length. This tool encodes that official prefix map and checks length and hyphen placement; it does not contact the IRS, prove that a business exists, or confirm that the entity is authorized to hire or invoice.
Knowing the difference between format validation and registry lookup avoids false confidence when an onboarding form accepts any nine digits that merely look like an EIN.
How to validate an EIN and read the campus result
Send an ein field with nine digits, optionally written as XX-XXXXXXX with a single hyphen after the two-digit prefix. For known prefixes the response includes campuses as an ordered list of campus or channel names and campus as those names joined for display. When the prefix is not assigned, valid is false, campuses are omitted, and reason explains that the prefix is not a valid IRS EIN campus prefix.
Empty strings, missing ein, non-digit characters, lengths other than nine, and numeric values that lost a leading zero (use a string for prefixes such as 01) fail before any table lookup and are not billed. Prefer this specialized EIN checker when search intent and product copy are about US Employer Identification Numbers and campus prefixes rather than a generic multi-country tax-ID utility.
Where EIN format checks fit payroll, banking, and vendor workflows
Payroll and HR systems store an EIN on every employer tax deposit and Form 941 path; a single transposed digit during company setup can send filings to the wrong account until the error is found months later. Validate at entry and block the save when valid is false, showing the reason and, when the prefix is known, the campus for support tickets.
Accounts-payable and vendor-master teams re-key EINs from W-9 PDFs and paper; batch-checking a CSV column quarantines rows whose prefix is not on the IRS list or whose length is wrong before the first 1099 run. Banks and payment platforms that collect business tax IDs for KYC can reject OCR noise and partial captures without calling an external registry, reducing false positives from free-text fields.
Product teams that already expose a multi-country tax-ID checker should still use this EIN-specific capability on US employer fields so the guide, FAQ, and campus output match what US operators search for. Do not treat a passing EIN format and prefix check as proof that the business is correctly identified, active with the IRS, authorized to hire, or present in any official registry—it only proves the digit string matches the published nine-digit layout and a known campus or online prefix.
What you can do with it
Gate EIN fields on company and vendor forms
When a user submits an EIN, validate format and prefix and block the save when valid is false, showing reason and campus so clerks can correct a mistype before the ERP record is written.
Audit EIN columns in payroll and partner files
Batch-validate every Employer Identification Number in a CSV import and quarantine rows whose prefix is not on the IRS campus table or whose length is not nine digits.
Explain campus origin in support and onboarding
Show the assigning campus (or Internet / SBA channel) from the two-digit prefix when customers ask where their EIN came from or whether an online application was used.
FAQ
What is a US Employer Identification Number (EIN)?
It is a nine-digit federal tax ID the IRS assigns to businesses and other entities, usually written XX-XXXXXXX, with a two-digit prefix that indicates the assigning campus or online channel.
How does this US EIN format validator work?
The response includes valid, prefix, serial, formatted, and when the prefix is known, campus and campuses from the IRS table.
Which EIN prefixes are considered valid?
Only two-digit prefixes listed by the IRS for campuses (Andover, Atlanta, Austin, Brookhaven, Cincinnati, Fresno, Kansas City, Memphis, Ogden, Philadelphia), Internet assignment, and the SBA. Unknown prefixes make valid false.
What happens with letters, spaces, or wrong length?
Provide digits 0-9 only (optional single hyphen after the two-digit prefix). Failed validation tasks are not billed.
Is the US EIN format validator free?
The browser tool is free and runs locally.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/enc/ein-us \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"ein":"12-3456789"}'const res = await fetch("https://api.kit.forhosting.com/enc/ein-us", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"ein": "12-3456789"
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/enc/ein-us",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"ein": "12-3456789"
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/enc/ein-us", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"ein":"12-3456789"}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"ein":"12-3456789"}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/enc/ein-us", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"ein": "12-3456789"
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "enc.ein_us",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
Malformed input—letters, wrong length, or illegal hyphen placement—is rejected with invalid_input instead of being silently stripped. Use it free in the browser or call the KIT API at the published price; both paths run the same deterministic rules with no network lookup and no IRS registry query.
How to validate an EIN and read the campus result
Leading and trailing spaces are trimmed; letters, other punctuation, internal spaces, double hyphens, or a hyphen in the wrong place are rejected as malformed input with invalid_input so you never accept a silently cleaned value. When the string is well formed, the engine returns ein as the pure nine-digit string, formatted as XX-XXXXXXX, prefix and serial as the split parts, valid true only when the prefix is on the IRS table and the serial is not all zeros, and prefix_valid for the campus-table check alone. Because the path is pure parse with no clock, random source, or network, the same input always yields the same JSON on the free browser tool and on the API. At $0.002 per successful request you can gate vendor imports, payroll onboarding, and form submits without negotiating a custom tier.