A Tax ID Number Is Your Identifier With the IRS
A Tax ID Number is a nine-digit code the Internal Revenue Service (IRS) uses to identify you for tax purposes. The IRS assigns it to you, and you use it on tax forms, W-4s, bank accounts, and anywhere else the government or financial institutions need to track your tax record. If you work, own a business, or file taxes, you have one — or you need one.
There are two main types. If you are an individual, your Tax ID Number is your Social Security Number (SSN). If you own a business, hire employees, or operate as a partnership or corporation, you need an Employer Identification Number (EIN) instead. Some people have both.
Key Takeaways
- Your Tax ID Number is either your Social Security Number (if you are an individual) or an Employer Identification Number (if you own a business or hire employees).
- The IRS uses your Tax ID Number to match your income, tax payments, and tax returns to your record.
- You need a Tax ID Number to open a bank account, get a job, file taxes, or apply for credit.
- You can request an EIN for free from the IRS by phone, mail, or online; the process takes minutes to a few days depending on the method.
Social Security Number vs. Employer Identification Number
If you are a sole proprietor — you work for yourself and do not hire employees — your Social Security Number is your Tax ID Number. You use it on your tax return, and the IRS links your business income to your personal tax record. You do not need to request anything; you already have it.
If you hire even one employee, operate a partnership, form an LLC, S-corp, or C-corp, or run a nonprofit, you must have an Employer Identification Number (EIN). The EIN is separate from your Social Security Number. You use the EIN on payroll forms, business tax returns, and when you open a business bank account. The IRS will not process your business tax return without one.
Some sole proprietors request an EIN anyway — to keep their personal and business finances separate, or because a bank or client requires it. That is optional. But if you have employees, an EIN is required, not optional.
How to Get an Employer Identification Number
You can request an EIN from the IRS for free. There are three ways to do it, and the speed depends on which one you choose.
| Method | How It Works | Timeline |
|---|---|---|
| Online (IRS.gov) | Fill out Form SS-4 on the IRS website. You get your EIN immediately on screen. | Instant |
| Phone | Call the IRS Business and Specialty Tax Line at 1-800-829-4933. An agent fills out the form with you and gives you the number by phone. | Same day (during business hours) |
| Print Form SS-4, fill it out, and mail it to the IRS address for your state. The IRS mails your EIN back. | Four to six weeks |
The online method is fastest and requires no phone call. You will need your Social Security Number, the date you started or plan to start your business, and basic information about your business structure and what it does. The IRS website walks you through each question.
If you call, have the same information ready. The phone line is open Monday through Friday, 7 a.m. to 10 p.m. Eastern Time. If you mail the form, include your name, address, and phone number so the IRS can contact you if there are questions.
Where You Will Use Your Tax ID Number
Your Tax ID Number appears on almost every financial or tax document you sign. Your employer uses it on your W-2. Your bank uses it to report interest you earn. If you own a business, you use it on your business tax return, payroll forms, and when you hire contractors.
You also provide it when you open a bank account, apply for a business loan or credit card, or hire employees. Financial institutions and the IRS use it to verify your identity and link transactions to your record. If you do not provide the correct number, the IRS may not receive the income reports, and you could face penalties or delays in processing your return.
If you are self-employed and file taxes, you will use your Tax ID Number on Schedule C (the self-employment income form) and on your 1040. If you own a business with employees, you will use it on Form 941 (quarterly payroll tax return) and Form 940 (annual unemployment tax return).
What Happens If You Lose or Forget Your Tax ID Number
If you lose your Social Security Number, contact the Social Security Administration. You can visit a local Social Security office or call 1-800-772-1213. They can issue you a replacement card. If you lose your EIN, you do not need a replacement card — the number itself does not change. You can look it up on the IRS website or call the IRS Business and Specialty Tax Line.
If you cannot remember your EIN, the IRS can tell you what it is. Call 1-800-829-4933 and have your Social Security Number and business information ready. The agent will look it up and give it to you over the phone. You can also check old tax returns or business bank statements — the EIN usually appears there.
Tax ID Numbers and Privacy
Your Tax ID Number is sensitive information. Protect it the way you would protect your Social Security Number. Do not share it in emails or texts unless you initiated contact with a known, trusted organization. Scammers sometimes pose as the IRS and ask for your Tax ID Number or Social Security Number over the phone. The real IRS will not call you out of the blue asking for this information.
If someone asks for your Tax ID Number and you are not sure whether they are legitimate, hang up and call the organization back using the phone number on their official website or statement. Never give your number to someone who called you first.
Frequently Asked Questions
Is my Social Security Number the same as my Tax ID Number?
If you are an individual and do not own a business, yes — your Social Security Number is your Tax ID Number. The IRS uses it to identify you on tax forms and match your income. If you own a business with employees, you need both: your Social Security Number and a separate Employer Identification Number.
Can I use my Social Security Number instead of an EIN for my business?
Only if you are a sole proprietor with no employees. If you hire anyone, you must have an EIN. Some sole proprietors request an EIN anyway to keep business and personal finances separate, but it is not required by law unless you have employees.
How long does it take to get an EIN?
Online is instant — you get the number on screen. By phone, you get it the same day during business hours. By mail, it takes four to six weeks. Most people use the online method because it is fastest and requires no waiting.
What if I never received my EIN in the mail?
Call the IRS Business and Specialty Tax Line at 1-800-829-4933 with your Social Security Number and business details. They can look up your EIN and give it to you over the phone. If the IRS never assigned one, they can issue it during the call.
Do I need a Tax ID Number to open a business bank account?
Most banks require an EIN if you are operating as anything other than a sole proprietor. Some banks will accept your Social Security Number for a sole proprietorship, but many prefer an EIN. Call your bank to ask what they need before you apply.