What a Tax Identification Number Is and Why You Need One

A Tax Identification Number Is How the Government Tracks Your Income and Tax Records

A Tax Identification Number (TIN) is a nine-digit code the Internal Revenue Service (IRS) uses to identify you for tax purposes. It appears on tax forms, W-2s, 1099s, and other documents you file with or receive from the government. Without one, you cannot file a tax return, open a bank account, or work legally in the United States.

The most common type of TIN is a Social Security Number (SSN), which you get from the Social Security Administration. But there are other types of TINs for specific situations — if you do not have an SSN, are self-employed, or run a business, you may need a different one.

The purpose is straightforward: the IRS uses your TIN to match income reports from employers, banks, and other sources to the tax return you file. This is how they know whether you reported all your income and whether you owe taxes or are due a refund.

Key Takeaways

A Tax Identification Number is a nine-digit code the IRS uses to track your income, tax filings, and tax history.
A Social Security Number is the most common type of TIN, but self-employed people, businesses, and non-citizens may need an Employer Identification Number (EIN) or Individual Taxpayer Identification Number (ITIN) instead.
You need a TIN to file a tax return, receive income, open a bank account, or work legally in the United States.
If you lose or forget your TIN, you can find it on past tax returns, W-2s, or by contacting the Social Security Administration or IRS directly.

The Three Main Types of Tax Identification Numbers

Social Security Number (SSN) is issued by the Social Security Administration to U.S. citizens, permanent residents, and certain temporary visa holders. It is the default TIN for most people who work or file taxes. You apply for an SSN at a Social Security office or online at ssa.gov, and you receive one number for life.

Employer Identification Number (EIN) is issued by the IRS to businesses, nonprofits, partnerships, and sole proprietors who hire employees. Even if you are self-employed and work alone, you may choose to get an EIN instead of using your SSN on business documents. You apply for an EIN online at irs.gov, and the IRS issues it immediately. An EIN is also called a Federal Employer Identification Number (FEIN).

Individual Taxpayer Identification Number (ITIN) is issued by the IRS to non-citizens who do not have an SSN but need to file a tax return or report income. This includes undocumented immigrants, visa holders, and foreign nationals with U.S. income. You apply for an ITIN by mail using Form W-7, and it takes four to six weeks to receive.

When You Need Each Type of TIN

You need an SSN if you are a U.S. citizen or permanent resident and plan to work, file taxes, or receive Social Security benefits. Most employers require an SSN before they will hire you. Banks also ask for an SSN when you open a checking or savings account.

You need an EIN if you own a business and hire employees, operate as a partnership or corporation, or run a nonprofit. Some sole proprietors without employees use an EIN on business tax forms instead of their SSN for privacy. The IRS does not charge a fee for an EIN.

You need an ITIN if you are not a U.S. citizen, do not have an SSN, but have income in the United States that must be reported to the IRS. This includes wages, self-employment income, rental income, or investment income. An ITIN allows you to file a tax return and claim refundable tax credits like the Earned Income Tax Credit (EITC), even if you are not authorized to work.

How to Find Your Tax Identification Number

If you have an SSN, it appears on your Social Security card. You can also find it on past tax returns (Form 1040), W-2 forms from employers, 1099 forms from banks or clients, or statements from the IRS.

If you have lost your Social Security card or do not remember your number, contact the Social Security Administration at 1-800-772-1213 or visit ssa.gov. You will need to provide your name, date of birth, and place of birth. Bring a photo ID and proof of citizenship or legal residency to a local Social Security office to request a replacement card.

If you have an EIN, the IRS sent it to you by mail when you applied. Check any business tax documents, bank statements, or loan applications — your EIN appears on all of these. If you cannot find it, you can look it up on the IRS website using your business name and address, or call the IRS Business and Specialty Tax Line at 1-800-829-4933.

If you have an ITIN, the IRS mailed it to you after you submitted Form W-7. Check the IRS letter you received or any tax returns you filed using that ITIN.

What Happens If You Do Not Have a Tax Identification Number

Without a TIN, you cannot legally work in the United States. Employers are required to verify your identity and work authorization using an I-9 form and a valid TIN. If you do not have one, you cannot be hired.

You also cannot file a tax return or claim a refund. If your employer withheld taxes from your paycheck and you do not file a return, you will not receive a refund of the taxes you overpaid. Additionally, you cannot open a bank account, get a loan, or apply for most government benefits without a TIN.

If you are a non-citizen with U.S. income, you can still obtain an ITIN and file a tax return to report that income and claim refundable credits. This does not change your immigration status, but it ensures you are complying with tax law.

How Your Tax Identification Number Is Used

The IRS uses your TIN to match income reports to your tax return. When you work for an employer, they report your wages to the IRS using your TIN on a W-2 form. When you receive interest from a bank or dividends from investments, those institutions report it using your TIN on a 1099 form. The IRS compares these reports to the income you listed on your tax return to verify accuracy.

Your TIN is also used to track tax payments, refunds, and any taxes you owe. If you owe back taxes, the IRS uses your TIN to locate you and collect the debt. If you are due a refund, the IRS uses your TIN to deposit it into your bank account or mail you a check.

Banks and financial institutions also use your TIN to report interest and investment income to the IRS and to verify your identity when you open accounts or apply for loans. Employers use it to withhold the correct amount of federal income tax from your paycheck.

Frequently Asked Questions

Is a Tax Identification Number the same as a Social Security Number?

No. A Social Security Number is one type of Tax Identification Number. The IRS uses the term "TIN" to refer to any nine-digit code it uses to identify you for tax purposes — that includes SSNs, EINs, and ITINs. Most people have an SSN, so the terms are often used interchangeably, but they are not identical.

Can I get a Tax Identification Number if I am not a U.S. citizen?

Yes. If you are not a citizen but have income in the United States, you can obtain an Individual Taxpayer Identification Number (ITIN) by submitting Form W-7 to the IRS. An ITIN allows you to file a tax return and report income. It does not change your immigration status or give you work authorization.

What if my Tax Identification Number was stolen or compromised?

Contact the IRS immediately at 1-800-829-1040 and the Social Security Administration at 1-800-772-1213. Place a fraud alert with the three major credit bureaus (Equifax, Experian, and TransUnion) and consider freezing your credit. Monitor your credit report and tax transcripts for unauthorized activity. The IRS can issue you a new ITIN if yours was used fraudulently.

Do I need a Tax Identification Number to file taxes if I am self-employed?

Yes. If you are self-employed, you must have a TIN to file a tax return and report your business income. Most self-employed people use their Social Security Number. However, you can also obtain an Employer Identification Number (EIN) to use on your business tax forms instead, which provides additional privacy.

How long does it take to receive a Tax Identification Number?

A Social Security Number takes one to two weeks if you apply in person at a Social Security office, or up to four weeks if you apply by mail. An Employer Identification Number is issued immediately when you apply online at irs.gov. An Individual Taxpayer Identification Number takes four to six weeks after you mail Form W-7 to the IRS.

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.