What Is an EIN? The Employer Identification Number, Explained

Fact-checked by the LegalGlass editorial team against primary sources · Published Aug 6, 2026 · Last updated Aug 6, 2026

An EIN is a 9-digit federal tax ID (format 12-3456789) the IRS assigns to a business or other entity. Also called a Federal Tax Identification Number or FEIN, it identifies employers, partnerships, corporations, LLCs, estates, and trusts on federal tax filings. The IRS issues an EIN for free, and once assigned it is permanent - never reused or reassigned to another entity.

What an EIN Is (Plain English)

An Employer Identification Number (EIN) is a 9-digit number the Internal Revenue Service assigns to a business, tax-exempt organization, 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." It is the entity-level counterpart to the Social Security number an individual uses on a personal return.

An EIN is written as two digits, a hyphen, then seven digits - the format 12-3456789. That layout is what distinguishes it on paper from the other federal tax IDs: a Social Security number and an Individual Taxpayer Identification Number (ITIN) both use the nine-digit pattern XXX-XX-XXXX, while an EIN uses the two-then-seven pattern. All three are nine digits, but only the EIN identifies a business rather than a person.

The EIN goes by several names. The IRS and its Publication 1635 also call it a Federal Tax Identification Number, and many banks and vendors shorten that to "Federal Tax ID" or "FEIN" (Federal Employer Identification Number). These are all the same number. Despite the word "Employer," a business does not need to have employees to get one - sole proprietors, single-member LLCs, and other entities routinely obtain an EIN for banking, tax elections, or identity-protection reasons even with zero staff.

Why the EIN Exists (Legal Basis)

The EIN exists because federal law requires an identifying number on tax documents. Under 26 U.S. Code § 6109, "any person required under the authority of this title to make a return, statement, or other document shall include in such return, statement, or other document such identifying number as may be prescribed for securing proper identification of such person." Section 6109 also directs any person who must be identified on someone else's return to furnish that number on request.

For an individual, the statute makes the Social Security number the default identifying number. But businesses, partnerships, corporations, estates, and trusts are not individuals and do not have SSNs, so the IRS prescribes a separate identifier for them: the Employer Identification Number. The EIN is the number the IRS uses to match an entity's returns, deposits, and information reports to the correct taxpayer, in the same way an SSN ties a person to their filings.

Because § 6109 gives the Secretary of the Treasury authority to prescribe the form of these identifying numbers, the EIN - and the Form SS-4 process used to request one - is a creature of IRS regulation built on that statutory foundation. The practical effect is simple: if an entity has a federal tax obligation, it must have a taxpayer identification number, and for most entities that number is an EIN.

Who Needs an EIN

You need an EIN if your business or entity has a federal tax reason for one. According to the IRS Employer Identification Number page, you need an EIN if you:

• Have employees;
• Operate your business as a partnership or a corporation;
• Must pay employment taxes, or excise taxes such as those on alcohol, tobacco, or firearms;
• Withhold taxes on income (other than wages) paid to a non-resident alien; or
• Are a tax-exempt organization, estate, trust, retirement plan or IRA, or farmers' cooperative.

The About Form SS-4 page lists the entities that apply this way: "employers, sole proprietors, corporations, partnerships, estates, trusts, certain individuals, and other entities." A single-member LLC or sole proprietor with no employees is not always required to have an EIN and may be able to use the owner's SSN for income-tax reporting - but many still get one, because most banks require an EIN to open a business account and it keeps the owner's SSN off vendor and payroll paperwork. If you are forming a company, our how to form an LLC guide covers where the EIN fits in the sequence, and how to get an EIN covers the application step by step.

EIN vs. SSN vs. ITIN

An EIN, a Social Security number, and an ITIN are all nine-digit U.S. tax identification numbers, but they identify different taxpayers and come from different processes. An EIN identifies an entity; an SSN and an ITIN each identify an individual. The table compares them.

The short version: use an EIN for a business, estate, or trust; use an SSN if you are an individual eligible for one; and use an ITIN if you are an individual who is not eligible for an SSN. These roles can overlap in practice - the individual who owns a business uses their SSN or ITIN on their personal return while the business uses its EIN. If you need to find a number you already have, see our EIN lookup guide.

Is an EIN Free?

Yes. An EIN is free directly from the IRS. The IRS states plainly on its Get an Employer Identification Number page: "Beware of websites that charge for an EIN. You never have to pay a fee for an EIN." The online tool issues the number "immediately" once the application is approved, and the IRS says you can "get an EIN for free directly from the IRS in minutes."

Third-party services that advertise EIN "filing" or "registration" for a fee are reselling a free government process; the number they obtain is identical to the one you can get yourself at no charge. The only genuine cost is your time. Note the IRS limit on the online tool: you can apply for "only 1 EIN per responsible party per day," and your principal place of business must be in the U.S. or U.S. territories to use the online application.

This page is general information, not legal or tax advice. It does not tell you whether your specific entity must obtain an EIN - that turns on your facts. It explains what the number is and points you to the primary IRS sources so you can confirm your own situation.

Is an EIN Permanent?

An EIN is permanent. IRS Publication 1635, Understanding Your EIN, states: "An EIN is a permanent number. Once an EIN is assigned to an entity, it is never reused or reassigned to another entity." Unlike an ITIN, which expires after three consecutive years without use, an EIN does not lapse from disuse and is never issued to a second taxpayer.

Because the number is permanent, the IRS does not "cancel" an EIN. If a business closes, the EIN stays associated with that entity forever; the IRS can close the related business account, but the number itself is retired rather than deleted or reassigned. That permanence is why an EIN survives routine changes like a new business name, a new address, or a new bank - none of those events requires a fresh number. It also means you should keep the EIN assignment notice (the CP 575 confirmation) with your permanent records, since the IRS issues that confirmation only once.

When You Need a New EIN

You generally need a new EIN only when the ownership or legal structure of the entity changes - not when its name, address, or management changes. The IRS Do you need a new EIN? page sets the rules by entity type. Common triggers that do require a new EIN include:

• Sole proprietor who incorporates, forms a partnership, or declares bankruptcy;
• Partnership that incorporates, that a single owner takes over to run as a sole proprietorship, or that ends and is replaced by a new partnership;
• Corporation that receives a new charter from the secretary of state, becomes a subsidiary, changes to a partnership or sole proprietorship, or merges to create a new corporation;
• LLC that terminates and forms a new corporation or partnership; and
• A trust created with estate funds, or a trust that changes its classification (for example, revocable to irrevocable).

By contrast, the IRS says you do not need a new EIN when you change your business name or location, declare bankruptcy as a corporation, operate a division of a corporation, are the surviving corporation after a merger, or elect to be taxed as an S corporation. If you are deciding on tax status, our EIN guide and formation resources explain how an S-corp election works without a new number.

Single-Member LLCs and the EIN

A single-member LLC is the clearest example of when an EIN is optional versus required. For income-tax purposes, the IRS treats a single-member LLC as a "disregarded entity" by default, meaning the owner reports the LLC's activity on their own return. According to the IRS Single Member Limited Liability Companies page, a disregarded single-member LLC "generally must use the owner's social security number (SSN) or employer identification number (EIN) for all information returns and reporting related to income tax."

The LLC must, however, get its own EIN in two situations: "if it has any employees or if it will be required to file any of the excise tax forms" (such as Forms 720, 730, 2290, or 11-C). For those employment and excise taxes, the IRS says the LLC "is required to use its name and employer identification number (EIN)" rather than the owner's SSN. Even when not required, a single-member LLC often obtains an EIN to open a bank account or because a state tax rule calls for one. Owners without a Social Security number can still get the EIN - see can you get an EIN without an SSN?

The Responsible Party on an EIN Application

Every EIN application must name a "responsible party." The IRS defines this as "someone who owns, controls or exercises effective control over a business, nonprofit or other legal entity and directly or indirectly manages its funds and assets," and it must be a person, not another entity. On Form SS-4 you list the responsible party's name and taxpayer ID - a Social Security number or an ITIN - and if more than one person qualifies, you list the one you want the IRS to recognize.

This matters for founders without an SSN. Because the responsible party may identify with an SSN, an ITIN, or an existing EIN, a business can obtain an EIN even when its owner is a non-resident who does not have a Social Security number. Applicants who lack both an SSN and an ITIN cannot use the online tool but can still apply by phone, fax, or mail on Form SS-4. The IRS also limits volume: one EIN per responsible party per day, which prevents a single person from pulling many numbers in bulk.

Related Terms

• How to get an EIN (step-by-step)
• Can you get an EIN without an SSN?
• What is an ITIN?
• EIN lookup
• How to form an LLC
• EIN (glossary) - the one-line definition.
• EIN for a bank account · EIN for an LLC · S corp vs LLC · SE tax calculator · ITIN

Frequently Asked Questions

What does an EIN look like?

It is a 9-digit number written as two digits, a hyphen, then seven digits: 12-3456789. That differs from an SSN or ITIN, which use the pattern XXX-XX-XXXX.

How much does an EIN cost?

Nothing. The IRS states you never have to pay a fee for an EIN and issues it free in minutes online. Sites that charge to get one are reselling a free government service.

Is an EIN the same as a Tax ID number?

An EIN is one kind of federal Tax ID. The IRS also calls it a Federal Tax Identification Number or FEIN. SSNs and ITINs are Tax IDs too, but they identify individuals, not entities.

Does an EIN ever expire or get reused?

No. IRS Publication 1635 says an EIN is permanent and, once assigned, is never reused or reassigned to another entity. The IRS does not cancel EINs.

Do I need a new EIN if I change my business name or address?

No. The IRS does not require a new EIN for a name or location change. A new EIN is generally needed only when ownership or legal structure changes, such as incorporating.

Can I get an EIN without a Social Security number?

Yes. The responsible party on Form SS-4 may use an SSN, ITIN, or existing EIN, and applicants without an SSN can apply by phone, fax, or mail. See getting an EIN without an SSN.

Sources

1. IRS - Employer Identification Number (definition, who needs one, free, application methods).
2. IRS - About Form SS-4 (form title "Application for Employer Identification Number," who files it).
3. IRS - Get an Employer Identification Number (no fee, issued immediately, 1 EIN per responsible party per day, U.S. principal business).
4. IRS - Apply for an EIN online (online tool, responsible party TIN requirement, daily limit).
5. IRS - Do you need a new EIN? (per-entity rules on when a new EIN is and isn't required).
6. IRS - Responsible parties and nominees (definition of responsible party, SSN/ITIN requirement, must be a person).
7. IRS - Single Member Limited Liability Companies (disregarded entity, when a single-member LLC needs its own EIN).
8. IRS - Publication 1635, Understanding Your EIN (EIN is permanent, never reused or reassigned; Federal Tax ID name; format).
9. IRS - Taxpayer Identification Numbers (TIN) (EIN, SSN, ITIN as the federal tax IDs and their formats).
10. IRS - Individual Taxpayer Identification Number (ITIN comparison - individual, not entity).
11. IRS - About Form W-7 (ITIN application, contrast with the EIN's Form SS-4).
12. IRS - Instructions for Form SS-4 (line-by-line EIN application guidance, responsible party).
13. Cornell Legal Information Institute - 26 U.S. Code § 6109, Identifying numbers (statutory basis requiring an identifying number on returns).

LegalGlass provides general information for educational purposes and is not a law firm or a substitute for advice from a licensed attorney or tax professional. This page is information, not advice. Laws, forms, and processing times change; verify current requirements with the IRS before acting.