A Tax ID is a nine-digit number the IRS uses to identify you for tax purposes

A Tax ID (also called an Employer Identification Number or EIN) is a unique nine-digit number assigned by the Internal Revenue Service. The IRS uses it to track your tax account, whether you are filing as an individual, running a business, or managing a nonprofit. Think of it as your tax identification number — similar to how a Social Security number identifies you for other government purposes, a Tax ID identifies you specifically to the IRS.

You may hear Tax ID and EIN used interchangeably, but they are not exactly the same thing. An EIN is one type of Tax ID. Individuals typically use their Social Security number as their Tax ID when filing personal taxes. Businesses, partnerships, nonprofits, and trusts use an EIN instead. If you are self-employed or run a business with employees, you will need an EIN.

The IRS does not send you a Tax ID automatically. You request one, and the process is free. Once assigned, your Tax ID stays the same for the life of your business or entity — you do not need to renew it or reapply.

Key Takeaways

  • A Tax ID is a nine-digit number the IRS assigns to identify you or your business for tax purposes.
  • Individuals filing personal taxes use their Social Security number; businesses and nonprofits use an EIN instead.
  • You request a Tax ID from the IRS for free — it is not assigned automatically.
  • Once you have a Tax ID, it does not change and does not expire.

When you need a Tax ID versus using your Social Security number

If you are an individual filing personal income taxes, you do not need a separate Tax ID. Your Social Security number serves as your Tax ID on your tax return. The IRS already has it on file, and you use it to file with the IRS and to report income to employers.

You need a separate Tax ID (EIN) if you own a business, operate as a sole proprietor with employees, form a partnership, create a corporation or LLC, start a nonprofit organization, or manage a trust or estate. Even if your business has no employees, some banks and vendors require an EIN before they will open a business account or issue a 1099 form to you.

Self-employed people without employees sometimes use their Social Security number instead of an EIN, but many choose to get an EIN for privacy and accounting reasons. Using an EIN keeps your personal Social Security number off business documents and vendor records.

How to request a Tax ID from the IRS

You can request a Tax ID (EIN) online, by mail, by fax, or by phone. The online method is the fastest and most direct. Go to the IRS website, use the online EIN application tool, and you will receive your number immediately after you submit the form. You do not need to mail anything or wait for a letter.

If you apply by mail, send Form SS-4 (Application for Employer Identification Number) to the IRS address listed on the form. Processing takes about four weeks. By fax, you can send the same form and typically receive your EIN within four business days. By phone, you call the IRS Business and Specialty Tax Line and speak to a representative who will assign your number on the call.

You will need basic information to complete the request: your name, address, the business name and address, the type of business structure, and the reason you need the EIN. If you are applying on behalf of a business, you will also need the name and Social Security number or Tax ID of the person responsible for the business.

What happens after you receive your Tax ID

Once the IRS assigns your Tax ID, you will receive a confirmation letter in the mail (unless you applied online, in which case you can print your confirmation immediately). Keep this letter in a safe place — you will need to reference your Tax ID when filing taxes, opening business bank accounts, hiring employees, and reporting income to the IRS.

You do not need to do anything else with your Tax ID once you have it. It does not expire, and you do not renew it. If your business closes, you do not need to "turn in" your Tax ID or notify the IRS that you are no longer using it — though you should file a final tax return for the year the business ended.

If you lose your Tax ID number, you can look it up on prior tax returns, bank statements, or vendor documents. If you cannot find it anywhere, you can contact the IRS directly and they will provide it to you.

Tax ID versus other identification numbers

The IRS uses several different identification numbers, and it is easy to confuse them. Your Social Security number identifies you as an individual and is used for personal tax returns, employment, and benefits. An EIN (Tax ID) identifies a business entity and is used for business tax returns and payroll. A PTIN (Preparer Tax Identification Number) is used only by tax professionals who prepare returns for others.

If you are self-employed and file Schedule C (self-employment income) on your personal tax return, you still use your Social Security number as your Tax ID — you do not need an EIN unless you have employees or choose to get one for privacy. If you form an LLC or corporation, you must use an EIN instead of your Social Security number on business returns.

Frequently Asked Questions

Do I need a Tax ID if I am self-employed?

Not necessarily. If you are self-employed with no employees, you can use your Social Security number on your tax return. However, many self-employed people get an EIN anyway to keep their personal Social Security number off business documents and to make accounting easier.

How long does it take to get a Tax ID?

Online applications are processed immediately, and you receive your number right away. Mail applications take about four weeks. Fax applications typically take four business days. Phone applications are assigned during the call.

Does a Tax ID cost money?

No. Requesting a Tax ID from the IRS is free. Be cautious of third-party websites that charge fees to help you request one — you can do it directly through the IRS at no cost.

What if I already have a Tax ID and need to look up the number?

Check prior tax returns, business bank statements, or vendor documents where you provided the number. You can also contact the IRS directly and provide your business name and address, and they will give you the number.