A Tax ID Number Is a Nine-Digit Identifier the IRS Uses to Track You or Your Business

A Tax ID Number — also called an Employer Identification Number (EIN) or Individual Taxpayer Identification Number (ITIN) — is a nine-digit code the Internal Revenue Service assigns to identify you or your business for tax purposes. The IRS uses it to match your tax returns, income reports from employers and banks, and payment records.

If you are a sole proprietor with no employees, you may file taxes using your Social Security Number instead. But if you operate a business structure (partnership, corporation, LLC), have employees, or are a non-citizen resident, you will need a separate Tax ID Number. The number itself does not change; the IRS keeps it on file for your entire tax life.

Key Takeaways

  • A Tax ID Number is a nine-digit code the IRS uses to identify a business or individual for tax reporting, separate from a Social Security Number.
  • Sole proprietors without employees can use their Social Security Number to file taxes, but businesses with employees or certain structures must obtain an EIN.
  • Non-citizens who work in the United States can obtain an ITIN to file taxes and report income even without a Social Security Number.
  • You can request a Tax ID Number for free from the IRS by mail, phone, or online, and the process typically takes minutes to a few weeks depending on the method.

The Two Main Types: EIN and ITIN

An Employer Identification Number (EIN) is issued to businesses, nonprofits, trusts, and certain other entities. You need an EIN if you have employees, operate as a partnership or corporation, file certain tax forms, or want to open a business bank account. The IRS assigns EINs in a sequence; they are not tied to your personal identity the way a Social Security Number is.

An Individual Taxpayer Identification Number (ITIN) is issued to non-citizens who work in the United States and need to file taxes but do not have a Social Security Number. An ITIN allows you to report income, claim refunds, and meet tax obligations. It does not grant work authorization or change your immigration status — it is purely for tax reporting.

If you are a sole proprietor (self-employed, no employees, no business structure), you can use your Social Security Number on your tax return instead of obtaining an EIN. However, many sole proprietors obtain an EIN anyway to keep business and personal finances separate on IRS records.

When You Need to Get a Tax ID Number

You must obtain an EIN before you hire your first employee, even if you are a sole proprietor. You also need one if you operate as an LLC, S-corporation, C-corporation, partnership, or nonprofit. If you file certain tax forms — such as Form 1065 (partnership return), Form 1120 (corporate return), or Form 990 (nonprofit return) — the IRS requires an EIN.

You should obtain an ITIN if you are a non-citizen resident who works and earns income in the United States. You will need it to file a tax return, claim refunds, and report self-employment income. Some non-citizens also obtain an ITIN to open a bank account or obtain credit, though that is not the primary purpose.

If you are unsure whether you need a Tax ID Number, the IRS worksheet on Form SS-4 (the EIN request form) walks through the decision. You can also contact the IRS directly at 1-800-829-4933 to ask.

How to Request a Tax ID Number

The IRS offers three ways to request an EIN: online, by phone, or by mail. The online method is the fastest — you can receive your EIN immediately after completing Form SS-4 on the IRS website. You do not need to create an account; you simply fill out the form and submit it. This method is available Monday through Friday, 7 a.m. to 10 p.m. Eastern Time.

By phone, you call the IRS Business and Specialty Tax Line at 1-800-829-4933. An IRS representative will ask you the questions from Form SS-4 and issue your EIN on the spot. This also takes minutes. The phone line is open Monday through Friday, 7 a.m. to 10 p.m. Eastern Time.

By mail, you complete Form SS-4 and send it to the IRS address listed on the form. Processing by mail typically takes two to four weeks. You will receive your EIN by mail.

To request an ITIN, you must file Form W-7 (Application for IRS Individual Taxpayer Identification Number) with the IRS. You can submit it by mail or through an IRS-authorized representative (such as a tax professional or community organization). Processing takes two to six weeks. You will need to provide proof of identity and proof of tax residency in the United States.

What Information You Need to Provide

To request an EIN online or by phone, have the following ready: your legal business name, business address, mailing address (if different), the type of business structure (sole proprietor, LLC, corporation, etc.), the reason you are requesting the EIN, and the date you expect to start business operations. If you have a Social Security Number, you will provide that; if not, you can still request an EIN.

For an ITIN, you must provide Form W-7 along with documents proving your identity (such as a passport) and your tax residency status (such as a lease, utility bill, or bank statement showing your U.S. address). The documents must be originals or certified copies; photocopies are not accepted. You will mail these to the IRS address listed on Form W-7.

What Happens After You Receive Your Tax ID Number

Once you receive your EIN, you can use it immediately on business bank accounts, tax forms, and any document that asks for a Tax ID Number. The IRS begins tracking income and payments under that number. If you hire employees, you will use your EIN to file payroll tax forms and report wages.

If you receive an ITIN, you can use it to file a tax return and report income. The ITIN does not expire, but the IRS may deactivate it if you do not file a tax return for three consecutive years. If that happens, you can reactivate it by filing Form W-7 again.

You do not need to renew your Tax ID Number. Once issued, it remains valid for the life of the business or individual. If your business closes, you do not need to formally cancel the EIN — you simply stop using it and report the closure on your final tax return.

Frequently Asked Questions

Can I get a Tax ID Number if I do not have a Social Security Number?

Yes. If you are a non-citizen, you can obtain an ITIN using Form W-7. If you are a business owner without a Social Security Number, you can still request an EIN online or by phone — the IRS will issue one. You will need to provide your individual tax identification number or passport instead.

How long does it take to get a Tax ID Number?

Online or by phone, you receive your EIN immediately. By mail, it takes two to four weeks. An ITIN takes two to six weeks by mail. Processing times vary depending on IRS workload and whether your application is complete.

Do I need a Tax ID Number if I am self-employed with no employees?

No, you can use your Social Security Number to file taxes as a sole proprietor. However, many self-employed people obtain an EIN to keep business and personal finances separate on IRS records and to open a business bank account.

What if I lose my Tax ID Number or forget it?

You can look up your EIN on the IRS website using your business name and address, or call the IRS at 1-800-829-4933. The IRS will confirm your number. You can also find it on past tax returns or business bank statements.

Can I change my Tax ID Number?

No. Your Tax ID Number does not change. If your business structure or name changes, you may need to obtain a new EIN, but your original number remains on file with the IRS. Contact the IRS to discuss your specific situation.