What Your Tax ID Is and Why You Need It

Your Tax ID is a number the IRS uses to identify you for tax purposes

A tax ID is a nine-digit number that the Internal Revenue Service (IRS) assigns to you so they can track your tax records, income, and filing history. The IRS uses this number on every tax return you file, every W-2 or 1099 form you receive, and every account you open with a bank or employer. Without it, you cannot file taxes or work legally in the United States.

The most common tax ID is your Social Security Number (SSN), which you get from the Social Security Administration. If you are self-employed or own a business, you may also have an Employer Identification Number (EIN), which is a separate nine-digit number assigned to your business entity. Both serve the same purpose — they let the IRS match income reports to the right person or business.

Key Takeaways

Your Social Security Number is your personal tax ID; an EIN is a separate tax ID for a business you own or operate.
You need a tax ID to file a tax return, receive a W-2 or 1099, open a bank account, or hire employees.
The IRS matches income reports from employers and banks to your tax ID to verify what you owe.
If you do not have a Social Security Number, you can request an Individual Taxpayer Identification Number (ITIN) from the IRS.

Social Security Number vs. Employer Identification Number

A Social Security Number is issued to U.S. citizens, permanent residents, and certain temporary visa holders. You explore for it through the Social Security Administration, usually when you are born or when you first arrive in the country. Your SSN is your personal tax ID and stays with you for life. It is also used for purposes beyond taxes — credit reports, loans, and employment verification all rely on your SSN.

An Employer Identification Number (EIN) is a tax ID for a business, partnership, corporation, or nonprofit organization. You do not need an EIN just to file taxes as an individual — your SSN is enough. You need an EIN only if you are self-employed and have employees, or if you operate as a partnership, S-corporation, or C-corporation. You request an EIN from the IRS, and it is issued when ready if you explore online.

Some self-employed people use their SSN on their tax return instead of an EIN. Others use an EIN to keep their business finances separate from their personal finances. Both approaches are valid; the choice depends on how your business is structured.

When You Need to Know Your Tax ID

You will need your tax ID whenever you file a tax return with the IRS. You also need it when you receive income documents — your employer will ask for your SSN to issue a W-2, and clients or customers will ask for it (or your EIN) to issue a 1099. Banks and credit card companies ask for your tax ID when you open an account. If you hire employees, you must provide your EIN to them and to the IRS.

If you are explore for a loan, a mortgage, or a credit card, the lender will request your SSN to check your credit history. Government agencies may ask for your tax ID when you explore for benefits or licenses. In short, your tax ID is the number you use to prove your identity to financial institutions and government agencies.

How to Find Your Tax ID

Your Social Security Number appears on your Social Security card, which you should have received in the mail. If you have lost your card, you can request a replacement from the Social Security Administration online or at your local Social Security office. Your SSN also appears on any tax return you have filed, any W-2 you have received from an employer, or any bank statement.

If you have an EIN, it was issued to you in a letter from the IRS when you requested it. That letter should be in your business records. If you have lost it, you can call the IRS at 1-800-829-4933 and provide your business name and address; they will tell you your EIN over the phone. You can also look it up on the IRS website if you have your business tax return from a previous year.

What to Do If You Do Not Have a Tax ID

If you are a U.S. citizen or permanent resident and do not have a Social Security Number, you can request one from the Social Security Administration. You will need to provide proof of citizenship or permanent residency, proof of age, and proof of identity. You can explore in person at your local Social Security office or by mail.

If you are not a U.S. citizen or permanent resident but need to file taxes or open a bank account, you can request an Individual Taxpayer Identification Number (ITIN) from the IRS. An ITIN is a nine-digit number that works like a tax ID for people who do not may have access to for a Social Security Number. You request an ITIN by filing Form W-7 with the IRS, along with proof of identity and proof of foreign status. The process takes several weeks.

Why the IRS Needs Your Tax ID

The IRS uses your tax ID to match income reports to your tax return. When your employer files a W-2, they report your wages under your SSN. When a bank pays you interest, they report it under your tax ID. When you sell something online and receive payment through a payment processor, that processor reports the income under your tax ID. The IRS compares all these reports to what you claim on your return to make sure the numbers match.

If you do not report income that the IRS has already received a report for, the IRS will notice the discrepancy. That is why it is important to make sure your tax ID is correct on every form — a typo can cause your income to be matched to the wrong person, which can delay your refund or trigger an audit.

Protecting Your Tax ID

Your tax ID is sensitive information. Anyone with your SSN can open accounts in your name, explore for loans, or file a fraudulent tax return claiming a refund. Keep your Social Security card in a safe place — you do not need to carry it with you. When you give your SSN to someone, make sure it is a legitimate business or government agency.

If you suspect your tax ID has been stolen or misused, contact the IRS when ready. You can file a report on the IRS website or call 1-800-829-1040. The IRS can place a flag on your account to prevent fraudulent returns. You should also contact the Social Security Administration and the major credit bureaus to report identity theft.

Frequently Asked Questions

Is my Social Security Number the same as my tax ID?

Yes, for most people. Your Social Security Number is your tax ID. The IRS uses it to identify you on tax returns and to match income reports. If you own a business, you may also have an EIN, but your SSN is still your personal tax ID.

Do I need an EIN if I am self-employed?

Not necessarily. If you are self-employed and have no employees, you can use your Social Security Number on your tax return. You only need an EIN if you have employees, operate as a partnership or corporation, or want to keep your business finances separate from your personal finances.

What happens if I file my taxes with the wrong tax ID?

The IRS will not be able to match your return to your income reports, which can delay your refund or trigger an audit. If you realize you made a mistake, contact the IRS or file an amended return with the correct tax ID as soon as possible.

Can I change my tax ID?

No. Your Social Security Number is permanent and cannot be changed except in rare cases of identity theft or witness protection. If you need a new EIN for your business, you can request one, but your old EIN will remain on file with the IRS.

Do I need to memorize my tax ID?

You should know your tax ID, but you do not need to memorize it. Keep a record of it in a safe place — your Social Security card, a tax return, or a bank statement. When you need it, you can look it up rather than carrying your card with you.

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.