Where to Find Your Tax ID Number and What It Looks Like

Your tax ID number is either your Social Security number or an Employer Identification Number, depending on your work situation

If you work as an employee, your tax ID is your Social Security number — the nine-digit number on your Social Security card. If you own a business or operate as a sole proprietor, you may have an Employer Identification Number (EIN), which is a separate nine-digit number issued by the IRS. Some people have both. The number you use on your tax return depends on how you file and what kind of income you report.

You do not need to request or apply for a Social Security number if you already have one — it was assigned to you when you were born or when you first entered the country legally. An EIN, by contrast, is something you request from the IRS if your business structure requires one. The distinction matters because tax forms ask for different numbers depending on whether you are filing as an individual or a business.

Key Takeaways

Your Social Security number is your tax ID if you work as an employee; it appears on your Social Security card and in your Social Security account online.
An Employer Identification Number (EIN) is a separate nine-digit tax ID for business owners and is issued by the IRS, not Social Security Administration.
You can look up your Social Security number through your Social Security account at ssa.gov or by calling 1-800-772-1213.
To get an EIN, you file Form SS-4 with the IRS either online, by mail, or by fax; the process takes minutes online and you receive the number immediately.
Your employer will also have your tax ID on file, and you can request a copy from your HR or payroll department if you have lost it.

Finding your Social Security number

Your Social Security number is printed on your Social Security card. If you have the card, the nine-digit number is on the front. If you have lost the card or cannot locate it, you can look up the number through your online Social Security account at ssa.gov. To create an account, you will need your name, date of birth, Social Security number (or enough of it to verify), and an email address. Once logged in, your full Social Security number appears on the dashboard.

If you do not have online access or prefer to speak with someone, you can call the Social Security Administration at 1-800-772-1213. They are open Monday through Friday, 7 a.m. to 7 p.m. Eastern time. Have your name, date of birth, and a form of ID ready. They will verify your identity and read your number to you over the phone.

Your employer also has your Social Security number on file. If you need a copy, contact your HR department or payroll office and ask them to confirm the number they have for you. Many employers include it on pay stubs, though some redact it for security reasons.

Getting an Employer Identification Number

An EIN is a nine-digit number the IRS issues to businesses, partnerships, corporations, nonprofits, and some sole proprietors. You do not automatically receive one — you must request it. The fastest way is to apply online at irs.gov using Form SS-4. The online application takes about 15 minutes, and you receive your EIN immediately after submission. You can then print a confirmation letter right away.

If you prefer not to apply online, you can mail Form SS-4 to the IRS address listed on the form (it varies by state) or fax it to the fax number provided. By mail, the process takes about four weeks. By fax, it typically takes two to three weeks. The online method is faster and the IRS recommends it.

You will need basic information to complete the form: your legal business name, business address, the type of business structure (sole proprietor, partnership, corporation, etc.), and the reason you need the EIN. If you are a sole proprietor with no employees, you may not need an EIN at all — you can use your Social Security number instead. The IRS website has a tool that helps you determine whether you need one.

Where your tax ID appears on documents

Your Social Security number appears on your tax return (Form 1040 or similar), W-2 forms from your employer, 1099 forms for other income, and any correspondence from the IRS. It also appears on your Social Security statement, which you can view online through your ssa.gov account.

An EIN appears on business tax returns (Form 1120 for corporations, Form 1065 for partnerships, etc.), business W-2 forms, and any IRS notices sent to your business. If you have both a Social Security number and an EIN, use the Social Security number on your personal tax return and the EIN on your business return.

What to do if you have lost or forgotten your number

If you have lost your Social Security card, you can request a replacement from the Social Security Administration. Visit your local Social Security office in person, or apply online at ssa.gov/myaccount if you have already created an account. In-person replacement usually takes one to two weeks. You can also call 1-800-772-1213 to find the office nearest you.

If you have lost an EIN confirmation letter, you can retrieve it by logging into your IRS business account at irs.gov or by calling the IRS Business and Specialty Tax Line at 1-800-829-4933. Have your business name and address ready. The IRS can look up your EIN and send you a new confirmation letter by mail.

Protecting your tax ID number

Your Social Security number and EIN are sensitive information. Do not share them unless you are filing a tax return, applying for credit, or dealing with a government agency. Be cautious about providing them over email or to unknown callers. The IRS will never initiate contact by phone or email asking for your number — they contact you by mail first.

If you suspect your Social Security number has been compromised, contact the Social Security Administration at 1-800-772-1213 or visit ssa.gov. If you suspect your EIN has been misused, contact the IRS at 1-800-829-4933. Both agencies can place a fraud alert on your account and help you monitor for unauthorized use.

Frequently Asked Questions

Can I use my Social Security number instead of getting an EIN for my business?

Yes, if you are a sole proprietor with no employees, you can use your Social Security number on your business tax return instead of obtaining an EIN. However, if you hire employees, open a business bank account, or form a partnership or corporation, you will need an EIN. The IRS website has a worksheet to help you determine whether you need one.

How long does it take to get an EIN?

Online applications are processed immediately, and you receive your EIN right away. Faxed applications take two to three weeks. Mailed applications take about four weeks. The IRS recommends applying online for the fastest result.

What if I have never had a Social Security number?

You can apply for a Social Security number through the Social Security Administration. Visit your local Social Security office with proof of identity, age, and citizenship or legal immigration status. Processing typically takes two to three weeks. Call 1-800-772-1213 to find the office nearest you and learn what documents you need to bring.

Do I need to renew my tax ID number?

No. Your Social Security number and EIN do not expire and do not need to be renewed. They remain valid for your entire life (for Social Security numbers) or for as long as your business operates (for EINs). You only need to update your information with the IRS if your business address or structure changes.

This guide is for general information only and is not medical, financial, legal, or other professional advice. For decisions specific to your situation, consult a qualified professional. See our Editorial Policy.