What is an EIN?
Employer Identification Number, a nine-digit federal tax ID assigned by the IRS to businesses, nonprofits, and other entities operating in the United States.
Also known as: Employer Identification Number, Federal Tax ID, FEIN
An EIN is the business equivalent of a social security number, formatted as XX-XXXXXXX. The IRS issues one per legal entity at formation; you use it on tax filings, bank account openings, payroll registrations, and most B2B onboarding flows that need to verify a counterparty is a real US business.
EINs are not strictly secret (they appear on W-9 forms and many public filings) but they are also not freely searchable. Public databases exist for nonprofits (the IRS publishes 990 filings) and SEC-registered entities, but for private companies the EIN is something the company has to disclose in a contract or onboarding flow.
For brand-data and KYC use cases, the EIN is the canonical key for tying a website to a legal entity. Combined with NAICS or SIC for industry classification and a verified address, it is the minimum bar for "is this business real and who is it." Context.dev pulls EINs (where available) as part of company-data enrichment alongside DUNS numbers and ticker symbols.
In the wild
- A SaaS onboarding form asking for company name and EIN to provision a paid account
- A KYC pipeline matching the EIN on a W-9 to the EIN in IRS filings before approving an ACH transfer
- A business-data API returning EIN, NAICS, and address when given a domain