EIN Validator - Instantly Check Your Employer ID Number Format

Our free EIN Validator tool instantly checks if an Employer Identification Number (EIN) has a valid 9-digit format and a recognized IRS prefix.

Full original guide (expanded)

Audit: Complete

Formula (LaTeX) + variables + units

This section shows the formulas used by the calculator engine, plus variable definitions and units.

Formula (extracted text)

Let $E_s$ be the input string (EIN). Let $E_c$ be the "cleaned" string, $E_s$, with all non-numeric characters removed. Let $P$ be the prefix of $E_c$, $P = \text{substring}(E_c, 0, 2)$. Let $S$ be the set of valid IRS prefixes: $S = \{10, 12, 13, 14, 16, 20, 21, \dots, 99\}$. $\text{ValidFormat} = (\text{length}(E_c) = 9) \land (P \in S)$

Variables and units

T = property tax (annual or monthly depending on input) (currency)

Sources (authoritative):

Valid EINs and Prefixes List — irs.gov · Accessed 2026-01-19
https://www.irs.gov/businesses/small-businesses-self-employed/valid-eins
Home — calcdomain.com · Accessed 2026-01-19
https://calcdomain.com/
Lifestyle Everyday — calcdomain.com · Accessed 2026-01-19
https://calcdomain.com/lifestyle-everyday
Miscellaneous — calcdomain.com · Accessed 2026-01-19
https://calcdomain.com/subcategories/miscellaneous
Simple Loan Calculator — calcdomain.com · Accessed 2026-01-19
https://calcdomain.com/simple-loan-calculator
VAT Calculator — calcdomain.com · Accessed 2026-01-19
https://calcdomain.com/vat
Business Loan Calculator — calcdomain.com · Accessed 2026-01-19
https://calcdomain.com/business-loan-calculator
Profit Margin Calculator — calcdomain.com · Accessed 2026-01-19
https://calcdomain.com/margin

Changelog

Version: 0.1.0-draft
Last code update: 2026-01-19

0.1.0-draft · 2026-01-19

Initial audit spec draft generated from HTML extraction (review required).
Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
Confirm sources are authoritative and relevant to the calculator methodology.

Verified by Ugo Candido on 2026-01-19
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Formulas

(Formulas preserved from original page content, if present.)

Version 0.1.0-draft

Citations

Add authoritative sources relevant to this calculator (standards bodies, manuals, official docs).

Changelog

0.1.0-draft — 2026-01-19: Initial draft (review required).