What Is an EIN? How to Get One and When You Need It

An EIN (employer identification number) takes about fifteen minutes to obtain, costs nothing, and is the single cheapest piece of business administration there is. This guide covers what an EIN actually is, how it differs from the other identifiers, who has to have one, how to get it without paying anybody, and what to do when the paperwork has vanished.

The number also has three properties that trip people up, usually at the worst possible moment. You can only get one per day per responsible party, the person who owns or controls the entity. The original confirmation letter is issued once and never reissued. And an EIN is only one kind of taxpayer identification number (TIN), which is why forms asking for a TIN cause so much hesitation.

I build the people and records tooling for businesses without an HR department at FirstHR, and FirstHR is an onboarding and HR platform rather than a payroll provider. This is general information, not tax advice.

What an EIN Is

An EIN is a nine-digit number the IRS assigns to a business or other entity to identify it for federal tax purposes. The IRS describes it as a federal tax ID number for businesses, tax-exempt organizations, and other entities (Internal Revenue Service). In practice it does for a business what a Social Security number does for a person.

The word employer in the name is misleading and causes real confusion. Plenty of entities that will never have an employee need an EIN, including single-member limited liability companies (LLCs) opening a bank account, estates, trusts, and non-profits. Having one does not mean you are an employer, and it does not create any obligation by itself.

It is also not a state registration. A federal EIN gets you nothing at the state level, and the withholding and unemployment accounts you need in order to actually run payroll are separate applications with separate numbers, in every state where you have somebody working.

Some states give their own account a name that looks like the federal one. A state employer identification number, sometimes abbreviated to SEIN, is the account number a state revenue or labor department issues for withholding or unemployment. It is formatted however that state formats it, and it never replaces the federal number on a federal filing.

What an EIN Looks Like

An EIN is nine digits written as two, then a hyphen, then seven. The pattern looks like 12-3456789, and that shape is the whole format. There are no letters in it, the length never varies, and every EIN number example you come across follows it, whether the entity is a two-person LLC or a national chain.

The first two digits are the only part with an official explanation. According to the IRS, they show the campus that assigned the number, or that the application came through the online route, and the agency publishes the full list of valid prefixes. Most people assume the prefix points to a state, but that list maps each one to an issuing office instead.

A Social Security number is also nine digits, but it is written three, then two, then four: 123-45-6789. The hyphen positions are the quickest way to tell which kind of number somebody has already written on a form, before you check anything else about it.

Then there are the names. FEIN stands for federal employer identification number, and it means the same thing as EIN. So does the FEI number the Florida Division of Corporations asks for on entity filings, and so does the federal tax identification number a bank wants on an account application. One number, several labels, one free application.

TIN vs EIN vs SSN

These three get used interchangeably, but only two of them are numbers. A taxpayer identification number (TIN) is the umbrella category, an EIN identifies a business, and a Social Security number (SSN) identifies a person. Getting that relationship straight resolves most of the hesitation people feel when a form asks for a TIN.

The practical consequence shows up on Form W-9, which asks for a taxpayer identification number and expects a specific one depending on the entity type. According to the IRS instructions printed on Form W-9 (March 2024), a corporation gives its EIN and a sole proprietor may give either a Social Security number or an EIN.

Under the same instructions, a single-member LLC that is disregarded for tax, meaning the IRS treats it as part of its owner rather than as a separate taxpayer, gives its owner's number.

A disregarded LLC that enters its own EIN under its owner's name, or a corporation that enters a Social Security number, has produced a name and number pair that will not match IRS records. The mismatch surfaces months later as a notice.

None of this is related to the internal employee numbers a business assigns for its own records, which are a purely administrative convenience with no tax meaning at all.

Who Needs One

The requirement attaches to what the business does rather than to its size. Any one of the first four situations below is enough on its own, and the last three are where the answer gets less clear-cut.

That last row is the reason a lot of one-person businesses apply when they technically do not have to. Without an EIN, every 1099 you send carries your Social Security number in full, and so does every W-9 you hand to a client. Those copies then sit in filing systems you have no control over.

Partial masking does not protect you as the sender. According to the IRS General Instructions for Certain Information Returns (2025), a filer may truncate the recipient's number on most payee copies, printing only part of it, but a filer's own number may not be truncated on any form. Fifteen minutes of paperwork removes that exposure permanently.

How to Get One

Apply directly with the IRS, which states that you never have to pay a fee for an EIN and that the online route delivers the number in minutes (Internal Revenue Service). No third party can get it faster, because the free online route is already immediate.

Fax and mail both use Form SS-4, the paper version of the application. According to the IRS instructions to Form SS-4 (December 2025), a faxed application comes back in about four business days and a mailed one takes approximately four weeks. When a date is already fixed, neither is worth choosing: apply online and keep paper as the fallback.

Whichever route you take, the form asks for the same handful of facts about the entity and the person behind it. Have them written down before you start, because the online session is the one place where going to look something up costs you the whole application.

When the online application stops with a reference number

The session does not always end with a number. It can stop and display a reference number instead, and which reference number you get decides the next step.

Under the Internal Revenue Manual, the procedures handbook IRS staff work from, reference numbers 101 and 115 go to a customer service representative. Every other one gets an automated message explaining how to correct the details and resubmit, or how to send Form SS-4 by mail or fax.

A 101 or a 115 is not a retry problem. Something in the entity details needs a person to look at it, so the next step is either the business and specialty tax line or Form SS-4 on paper.

The Form SS-4 instructions list 855-641-6935 as the fax number for applicants whose principal business is in one of the 50 states or the District of Columbia, and paper applications go to the EIN Operation in Cincinnati.

The One-Per-Day Limit

The IRS limits issuance to one EIN per responsible party per day, and the agency's Publication 1635 states that the limit applies to all requests, whether online, by fax, or by mail. It has been in force since May 21, 2012, and the stated reason is to ensure fair and equitable treatment for all taxpayers.

For most businesses it never comes up. It matters if you are setting up several entities at once, because it turns an afternoon of applications into a schedule, and it is worth knowing before you tell a bank or a landlord that you will have a number tomorrow.

The limit is per responsible party rather than per person applying, so genuinely separate entities with different responsible parties are not caught. Naming different responsible parties purely to get around the limit is not the same thing, and the responsible party is meant to be a real answer rather than a routing decision.

The Responsible Party

Every EIN application names a responsible party: the individual who ultimately owns or controls the entity, or who exercises effective control over it. The IRS is explicit that the responsible party must be a person and not an entity, with government entities as the only exception (Internal Revenue Service).

This is the field people fill in casually and then never revisit, which is where the trouble starts. IRS letters go to the entity's mailing address. The responsible party, though, is the person the IRS recognizes as controlling the entity, and in practice the person a bank calls when something needs verifying. When that person leaves, the record stays pointed at them until somebody updates it.

The same form reports a change of business address, which is the version people do remember, usually because mail stops arriving. Adding the responsible party check to whatever routine already covers an address change is the cheapest way to stop this drifting.

CP 575 and Letter 147C

When the IRS assigns an EIN, it issues a CP 575 notice confirming it, once. Under IRS procedure, an online applicant can view, save, and print it at the end of the session, and whoever does not take that option gets it by mail at the address on the application.

That original notice is never reissued. If it is gone, no amount of asking produces another copy, and the replacements are a Letter 147C or the digital CP575 described below.

This matters because banks, payroll providers, and state agencies frequently ask for the confirmation letter rather than for the number, so an owner who knows the EIN by heart can still be stuck. Knowing the 147C exists, and that it is an official substitute rather than a second-best, turns a week of confusion into a phone call.

The lesson people take from this is usually the right one: save the CP 575 the day it arrives, in the place where the business keeps its formation documents rather than in the inbox of whoever happened to apply. You will want it in three years.

What the EIN letter is, and how to get a copy

The EIN letter is the CP 575, the IRS notice confirming the number the agency assigned to the entity. It is unremarkable to look at, which is why almost nobody recognizes it until a bank asks for it by name.

The IRS suggests keeping several copies, because the notice can be used whenever EIN verification is requested for business purposes, such as opening a bank account. There is now another route to a copy, and it is newer than most guidance on this subject.

According to the IRS, a digital CP575 is available through Business Tax Account, the IRS online account for businesses, and can be used as a substitute for the original CP575 notice series and for Letter 147C (Internal Revenue Service). The original is still issued only once, so pull the digital copy and file it before anybody asks.

When You Need a New One

An EIN belongs to an entity, not to a business name or an address, which is what decides whether a change requires a new number. The IRS sorts the question by entity type: renaming or relocating does not require a new number, while changing what the entity fundamentally is usually does (Internal Revenue Service).

The rows in the middle, where the entity itself changes, are where a small business most often gets it wrong. The usual slip is continuing to file under the old number after incorporating, because the bank account and the payroll setup already point at it.

Correcting filings made under the old number is more work than the original application would have been, and it reaches into every return filed in between. The IRS sets out the full picture in Publication 1635.

Where You Actually Use It

Once you have the number, it appears in more places than most owners expect, and consistency across them is what keeps the filings matching.

Keeping the number, the CP 575, and the state account numbers in one findable place is unglamorous, but it is what makes the first audit, the first bank change, or the first payroll provider migration take an hour instead of a week.

FirstHR is built to carry that kind of record alongside the employee file. The register below is the plainest version of it: one row per number, and a column saying where the paper that proves it is filed.

Are EIN numbers public?

Partly, and it depends on the entity. No government directory covers every business, so there is no single place to type in a company name and read back its EIN. Federal law also keeps the tax return information behind the number confidential (26 U.S.C. 6103). The number itself, though, is not secret.

Some categories are openly published. The IRS Tax Exempt Organization Search shows exempt organizations along with the Form 990 returns they file, a public company reports its employer identification number on the cover page of SEC filings such as the annual Form 10-K, and Florida lets anyone search its corporate registry by FEI number.

For a private company the number is public only where it has already been handed over: a W-9 sitting with a client, a license application, a court filing, a state registration. Treat it like a business bank account number rather than a Social Security number, and keep a record of who has been given it.

How to find the EIN of another company

Ask the company for it. If you need a vendor or contractor number so you can file a 1099, the route is a completed Form W-9 rather than a search, and collecting one before you pay the first invoice is the version of this that never goes wrong.

Searching only works on the categories that publish. For an exempt organization, use the IRS Tax Exempt Organization Search. For a public company, look at the cover page of its SEC filings, where it prints its employer identification number. And a few state registries carry the number, which is why Florida entity searches accept an FEI number.

A state-level lookup, whether in Pennsylvania or elsewhere, searches that state's own business register rather than IRS records, so it can return a federal number only where the state itself publishes one.

Where Small Employers Get This Wrong

There are five patterns, and none of them is about filling in the application itself.

Paying a service for something that is free is first, and it is the most common. The IRS route costs nothing and is instantaneous; a paid intermediary adds a fee and no speed.

Losing the CP 575 is second. The original is issued once and never reissued, which almost nobody knows until the moment a bank asks for it.

Assuming a federal EIN covers state obligations is third. It does not. State withholding and unemployment registrations are separate and are what actually let you pay somebody legally in that state.

Continuing to file under the old number after an entity change is fourth. The number belongs to the entity, and incorporating creates a new entity that needs its own number, whether or not the bank account changed.

And leaving a departed founder as the responsible party is last. It is a 60-day obligation that is easy to miss, and it quietly leaves the IRS recognizing somebody who no longer works there as the person in control of your business. Adding it to the same checklist as an address change is all the fix requires.

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