Who needs a EIN in United States, how to register with Internal Revenue Service (IRS) and state departments of revenue, what the number looks like, how to find or check one, and where it goes on your invoices.
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Updated for 2026
Last reviewed September 2026
What the EIN is
The EIN is the number Internal Revenue Service (IRS) and state departments of revenue assigns to a taxpayer in United States. It follows you across every tax you deal with: Sales tax, income tax and withholding. Businesses that pay you will ask for it before they release payment, because they report their suppliers to Internal Revenue Service (IRS) and state departments of revenue by this number.
EIN: nine digits as 12-3456789. SSN: 123-45-6789.
Who needs one
Individuals use their SSN or ITIN. Businesses with employees, corporations, partnerships and most LLCs need an EIN; a sole proprietor without staff can use an SSN, but an EIN keeps it off invoices.
How to register, step by step
Apply for an EIN free on IRS.gov; the number is issued immediately.
Sole proprietors and single-member LLCs apply with an SSN or ITIN; foreign owners fax or mail Form SS-4.
Register separately with your state for a sales tax permit if you sell taxable goods or services there.
Give clients a Form W-9 with your EIN so they can issue a 1099.
How to find or check a EIN
The EIN is on the IRS confirmation letter (CP 575); call the IRS Business and Specialty Tax Line if you lose it. Paid EIN lookup sites charge for what the letter shows free.
Where it goes on your paperwork
In the invoice header next to your business name, and in the client block when the client is a registered business. Quotations and purchase orders carry it too, so the client's accounts team can match documents. The United States invoice generator has a EIN field in both blocks.
Questions people ask
Does it cost anything to get a EIN?
Registration with Internal Revenue Service (IRS) and state departments of revenue is normally free. Agents charge for filling in the same form; pay one only if you want the time saved.
Can I invoice without a EIN?
You can write the document, but many clients will not pay an invoice that has no EIN, and you cannot charge Sales tax without being registered. Register first; it is usually quick.
Is the EIN the same as Sales tax registration?
Not necessarily. The EIN identifies you as a taxpayer; Sales tax registration is a separate status you take on when turnover passes the threshold or you opt in. Some countries use one number for both, others issue a separate Sales tax number.
How long does registration take?
Online registrations are often instant or take a few days; applications that need a visit or document checks take longer. Start before you need to send your first invoice.
Written from published tax-authority guidance and reviewed on 2026-09-03. Everything here is indicative rather than a ruling on your circumstances, and rules change. Confirm anything you rely on with Internal Revenue Service (IRS) and state departments of revenue before acting on it, and tell us if you find something out of date so we can correct it.
This guide explains the rules in general terms and is not tax advice for your circumstances. Confirm your position with a qualified adviser or with Internal Revenue Service (IRS) and state departments of revenue.
🇺🇸 United States
Tools for United States
Invoices, quotations, purchase orders, credit notes and waybills in USD, with Sales tax and the EIN on the document. Plus a Sales tax calculator and a salary tax calculator. Everything runs in your browser and nothing is uploaded.