If you’ve spent more than five minutes researching how to start a business, you’ve probably run into the term EIN. It sounds like government jargon because it is government jargon — but it’s also one of the first things you’ll need to get right. An EIN, or Employer Identification Number, is essentially a Social Security number for your business. The IRS assigns it, it’s nine digits long, and you’ll use it for everything from opening a business bank account to filing your taxes.

Getting one is free, takes about five minutes online, and you don’t need a lawyer or an accountant to do it. The catch: a surprising number of business owners still manage to get it wrong — applying through paid third-party services, using the wrong number on tax forms, or not realizing they need a new EIN after restructuring their business.

What an EIN Actually Is and Why It Exists

An Employer Identification Number is a unique nine-digit number the IRS assigns to business entities for tax reporting purposes. Think of it as your business’s fingerprint in the federal tax system. The format looks like XX-XXXXXXX, and once it’s assigned, it stays with your business for its entire life.

The name is a bit misleading. You don’t need employees to need an EIN. The IRS originally created EINs to track employment tax obligations, but the number has evolved into a general-purpose business identifier. Banks require it. State tax agencies reference it. Vendors ask for it on W-9 forms. If your business interacts with the financial system in any meaningful way, your EIN is going to come up.

Every business structure can get one. Sole proprietorships, partnerships, LLCs, S-corps, C-corps, nonprofits, trusts, and estates all qualify. Even if you’re a one-person LLC working from your kitchen table, you’re eligible — and in most cases, you should get one.

The IRS uses your EIN to track your business’s tax filings, payments, and reporting obligations. It’s the thread that ties together your quarterly estimated payments, your annual returns, your payroll tax deposits, and any information returns (like 1099s) you file. Without it, you’re essentially invisible to the federal tax system as a business entity.

Who Needs an EIN and Who Can Skip It

Not every business owner technically needs an EIN, but the list of situations where you do need one is longer than most people realize. According to the IRS guidelines, you’re required to get an EIN if you have employees, operate as a corporation or partnership, file employment tax returns, withhold taxes on income paid to a non-resident alien, have a Keogh plan, or are involved with trusts, estates, real estate mortgage investment conduits, nonprofits, farmers’ cooperatives, or plan administrators.

That covers a lot of ground. But here’s the scenario where it gets interesting: the solo freelancer operating as a sole proprietorship with no employees. Technically, the IRS says you can use your Social Security number instead of an EIN. You’re not required to get one. But you should get one anyway.

Why? Because your SSN is the skeleton key to your identity. Every time you hand it to a client on a W-9, you’re increasing your exposure to identity theft. An EIN costs nothing, takes minutes to obtain, and lets you keep your SSN out of circulation. The SBA recommends that all business owners obtain an EIN regardless of whether they’re legally required to have one.

If you’re forming an LLC — even a single-member LLC — most states will require an EIN for state tax registration. And if you ever want to open a business bank account, the bank is going to ask for one. So even if you technically don’t need it today, you’ll almost certainly need it tomorrow.

The one group that genuinely can skip it: sole proprietors with no employees, no Keogh plan, and no excise tax obligations who don’t mind using their SSN on tax documents. That’s a narrow group, and it gets narrower every year.

How to Apply for an EIN (It’s Free and Instant)

This is the part where the government actually makes things easy, which should tell you how straightforward the process is. The IRS online EIN application is available Monday through Friday, 7 a.m. to 10 p.m. Eastern Time. You’ll answer a series of questions about your business structure, and at the end, you’ll receive your EIN immediately. No waiting period. No processing time. It’s generated on the spot.

You’ll need a few things before you start. The responsible party — that’s the person who controls or manages the entity — needs a valid Taxpayer Identification Number (SSN or ITIN). You’ll need to know your business structure (LLC, corporation, partnership, etc.), your reason for applying, and your principal business activity. The whole thing takes about ten minutes if you’re organized, five if you’ve done it before.

There are other ways to apply if the online method doesn’t work for you. You can fax or mail Form SS-4 to the IRS. Fax applications typically get a response within four business days. Mail applications can take four to five weeks. International applicants who don’t have an SSN or ITIN can call the IRS directly at 267-941-1099.

A word of caution about third-party EIN services. You’ll find dozens of websites that charge $50 to $300 to “help” you get an EIN. They’re filling out the same free IRS form you can fill out yourself. Some of these services are legitimate — they bundle EIN applications with other business formation tasks — but many are just reselling a free government service at a markup. If all you need is an EIN, go directly to IRS.gov. Don’t pay for something that’s free.

One more thing: you can only get one EIN per responsible party per day through the online system. If you’re setting up multiple entities, plan accordingly.

After you receive your EIN, save the confirmation notice (CP 575) in a secure location. This is the official IRS document confirming your number, and you’ll need it when opening bank accounts, applying for business licenses, or responding to IRS correspondence. If you lose it, you can call the IRS Business and Specialty Tax Line at 800-829-4933 to retrieve your EIN, but the process takes longer than you’d like and requires identity verification. Treat the CP 575 like you’d treat a birth certificate — don’t lose the original.

EIN vs. SSN vs. ITIN: What’s the Difference and When Do You Need a New EIN?

These three numbers get confused constantly, and mixing them up on tax forms can create headaches that take months to resolve. Understanding the distinctions will save you from filing corrections and dodging IRS notices.

Your Social Security Number is a nine-digit number assigned to U.S. citizens and authorized residents by the Social Security Administration. It’s primarily used for tracking earnings and benefits. When you use it for business purposes, you’re using a personal identifier in a commercial context — which is why it creates identity theft risk. Every W-9 you hand to a client with your SSN is another opportunity for that number to end up somewhere it shouldn’t.

An Individual Taxpayer Identification Number is a nine-digit number the IRS issues to individuals who need a U.S. taxpayer identification number but aren’t eligible for a Social Security number. It’s formatted like an SSN (XXX-XX-XXXX) and starts with the number 9. Foreign nationals, non-resident aliens, and their dependents commonly use ITINs. If you’re a non-U.S. citizen starting a business in the United States, your ITIN is how you interact with the tax system until you’re eligible for an SSN. Note that ITINs need to be renewed periodically — they expire if not used on a tax return for three consecutive years.

Your EIN is the business equivalent. It identifies your business entity, not you personally. This distinction matters because business tax obligations are separate from personal ones (even for pass-through entities where income ultimately flows to your personal return). The EIN goes on business tax returns, payroll filings, and business financial accounts. Your SSN or ITIN goes on your personal return.

Here’s a common mistake: using your SSN where your EIN should go, or vice versa. If you’re a single-member LLC that’s elected to be taxed as an S-corp, you’ll use your EIN on Form 1120-S and your SSN on your personal 1040. If you mix them up, the IRS computers won’t match your filings correctly, and you’ll get a notice. It’s fixable, but it’s a pain that can delay your refund or trigger an unnecessary audit flag.

Another mistake: thinking your EIN replaces your SSN for all purposes. It doesn’t. Your EIN is for business tax purposes. Your SSN still goes on your personal tax return, your mortgage application, and your health insurance enrollment. They’re parallel systems, not replacements.

When your business changes, you might assume you need a new EIN. Sometimes you do. Sometimes you don’t. The rules aren’t always obvious.

You do need a new EIN if you incorporate a sole proprietorship, if a partnership becomes a sole proprietorship (because a partner leaves), if a sole proprietorship becomes a partnership (because you bring on a partner), if you create a new corporation after a statutory merger, or if a new LLC with more than one owner is formed. Basically, if the fundamental legal structure of your entity changes, the IRS considers it a new entity and wants a new number.

You don’t need a new EIN if you change your business name, change your business location, add or close a bank account, change your accounting period, or — and this surprises people — if a sole proprietorship files for bankruptcy. The entity is the same; it’s just going through something.

For LLCs specifically, the rules depend on how many members you have and how you’ve elected to be taxed. A single-member LLC that’s been disregarded for tax purposes doesn’t need a new EIN if the owner changes — unless the new owner is an entity and not an individual. A multi-member LLC that loses all but one member needs a new EIN because it’s gone from being taxed as a partnership to being a disregarded entity.

If you’re unsure whether your situation requires a new EIN, the IRS has a helpful reference on business structures that walks through the various scenarios. When in doubt, a fifteen-minute call to a tax professional is cheaper than filing under the wrong number for a year.

One final point that trips people up: your EIN is permanent. Unlike a phone number or an address, you can’t cancel it, return it, or let it expire. Even if you close your business, the EIN remains assigned to that entity in the IRS’s records. If you start a new business later, you’ll need a new EIN — you can’t recycle the old one. Think of each EIN as a historical record of a specific business entity’s existence, from formation to dissolution.

The bottom line on EINs is simple: get one early, get it directly from the IRS, and store the confirmation notice somewhere safe. It’s a small administrative step that every business needs to take, and it’s one of the few interactions with the federal government that’s genuinely painless.

Frequently Asked Questions

How much does it cost to get an EIN?

It’s completely free. You can apply directly through the IRS website at IRS.gov, and you’ll receive your EIN instantly after completing the online application. Be careful with third-party websites that charge $50 to $300 to “help” you get an EIN. They’re filling out the same free form you can fill out yourself. Unless you’re bundling the EIN application with other business formation services, there’s no reason to pay anyone for this.

How long does it take to get an EIN number?

If you apply online through IRS.gov (available Monday through Friday, 7 a.m. to 10 p.m. Eastern), you’ll get your EIN immediately at the end of the application. There’s no waiting period. If you apply by fax using Form SS-4, expect a response within about four business days. Mail applications can take four to five weeks. International applicants without an SSN or ITIN can call the IRS at 267-941-1099.

Do I need an EIN if I'm a sole proprietor with no employees?

Technically, no. The IRS says sole proprietors with no employees can use their Social Security number instead. But most financial advisors recommend getting one anyway because it’s free, takes five minutes, and keeps your SSN out of circulation. Every time you put your SSN on a W-9 for a client, you’re increasing your exposure to identity theft. An EIN lets you avoid that risk entirely.

What's the difference between an EIN and an SSN?

An SSN (Social Security number) is a personal identifier assigned to U.S. citizens and authorized residents by the Social Security Administration. An EIN (Employer Identification Number) is a business identifier assigned by the IRS. Your EIN goes on business tax returns, payroll filings, and business bank accounts. Your SSN goes on your personal tax return and personal financial documents. They’re parallel systems, and one doesn’t replace the other.

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

Changing your business name alone doesn’t require a new EIN. Neither does changing your address, your bank account, or your accounting period. However, you do need a new EIN if the legal structure of your business changes, like incorporating a sole proprietorship, converting a partnership to a sole proprietorship, or forming a new LLC with multiple owners. The rule of thumb: if the fundamental entity type changes, the IRS wants a new number.

Can I look up my EIN if I lost it?

Yes, but it’s not instant. You can call the IRS Business and Specialty Tax Line at 800-829-4933, and they’ll help you retrieve your EIN after verifying your identity. The process takes longer than most people expect. That’s why the IRS confirmation notice (called the CP 575) that you receive when you first get your EIN should be stored securely, like you’d store a birth certificate. You can also find your EIN on previously filed tax returns or on the original confirmation letter.