What Your Tax ID Number Is and Where to Find It

Your Tax ID Number Identifies You to the IRS

A tax ID number is a nine-digit identifier the Internal Revenue Service (IRS) uses to track your tax account. For most people, this is your Social Security number (SSN). If you are self-employed, run a business, or operate as a partnership or corporation, you may have an Employer Identification Number (EIN) instead, which serves the same purpose for business tax filings.

The IRS uses your tax ID to match your income reports, deductions, credits, and payments to your account. When you file a tax return, report income to your employer, or open a business bank account, you will need to provide this number. Without it, the IRS cannot process your return or track whether you have paid what you owe.

Key Takeaways

Your tax ID is either your Social Security number (if you file as an individual) or an Employer Identification Number (if you own a business).
You can find your SSN on your Social Security card, tax returns, W-2 forms, or by contacting the Social Security Administration.
An EIN is a nine-digit number issued by the IRS and can be obtained for free through the IRS website or by mail.
You must provide your tax ID when filing returns, reporting income, opening business accounts, or explore for loans.
If you have lost or forgotten your tax ID, you can recover it through your Social Security account online or by contacting the IRS directly.

Social Security Number as Your Personal Tax ID

If you work as an employee or file taxes as an individual, your Social Security number is your tax ID. This is the same nine-digit number on your Social Security card. The IRS links all your W-2 forms, 1099 forms, and tax returns to this number.

You can locate your SSN on several documents: your Social Security card itself, any W-2 or 1099 form you have received from an employer or client, previous tax returns, or your Social Security statement. If you do not have access to any of these, you can create a free account on the Social Security Administration website (ssa.gov) and view your number there, or call the Social Security Administration at 1-800-772-1213.

Employer Identification Number for Business Owners

If you own a business, partnership, or corporation, the IRS issues you an Employer Identification Number (EIN) instead of using your Social Security number for business purposes. An EIN is also nine digits and looks similar to an SSN, but it identifies your business entity to the IRS, not you personally.

You need an EIN if you have employees, operate as a corporation or partnership, file certain tax returns, or open a business bank account. You can obtain an EIN for free through the IRS website at irs.gov by completing Form SS-4 online, which takes about 15 minutes. The IRS will issue your EIN when ready. You can also explore by mail or fax, though this takes longer — typically two to four weeks.

Once you receive your EIN, the IRS will send you a confirmation letter. Keep this letter in your records. You will use this number on all business tax filings, payroll forms, and when reporting business income.

Where to Find Your Tax ID If You Have Lost It

If you cannot locate your tax ID number, the fastest way to recover it depends on which type you need. For a Social Security number, log into your account at ssa.gov using your username and password, or call 1-800-772-1213. The Social Security Administration can confirm your number over the phone or by mail.

For an EIN, check any IRS correspondence you have received — the confirmation letter sent when you first obtained the number, or any business tax return you have filed. You can also call the IRS Business and Specialty Tax Line at 1-800-829-4933 and provide your business name and address; they will look up your EIN. Have your business documents ready when you call.

If you have filed a tax return in the past, your tax ID will appear on that return. You can also request a transcript of your return from the IRS, which shows your tax ID and is useful if you need to verify the number for a bank or loan process.

Why the IRS Needs Your Tax ID Number

The IRS uses your tax ID to match income reported by your employers or clients to your tax account. When your employer files a W-2 or a client files a 1099, they report your tax ID along with the income amount. The IRS compares this to what you report on your own return. If the numbers do not match, the IRS will contact you.

Your tax ID also links all your tax filings together — returns, amended returns, payment records, and any correspondence with the IRS. This allows the IRS to track whether you have paid taxes owed, claimed credits you are may have access to to, and filed on time. Without a correct tax ID, your return may be delayed or rejected.

Protecting Your Tax ID Number

Your tax ID number is sensitive information. Treat it like you would your Social Security number: do not share it with people you do not trust, and do not carry your Social Security card in your wallet. Criminals can use a stolen tax ID to file a fraudulent return in your name and claim a refund, or to open accounts in your name.

Only provide your tax ID to your employer, your bank, the IRS, or other official institutions that have a legitimate reason to request it. If you suspect your tax ID has been stolen or misused, contact the IRS when ready at 1-800-829-1040 or file a report on the IRS website. You can also place a fraud alert with the three major credit bureaus (Equifax, Experian, and TransUnion) to prevent someone from opening accounts in your name.

Frequently Asked Questions

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

For most individuals, yes — your Social Security number is your tax ID. However, if you own a business, you may have both an SSN and a separate EIN. The EIN is used for business tax filings, while your SSN is used for personal returns.

Can I change my tax ID number?

You cannot change your Social Security number straightforward because you want to. The Social Security Administration only reassigns numbers in rare cases of identity theft or religious objection. For an EIN, you can obtain a new one if your business structure changes, but the old number remains on file with the IRS.

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

The IRS will likely reject your return or delay processing it. If the number belongs to someone else, it could cause problems for both you and that person. Contact the IRS when ready to correct the error and resubmit your return with the correct number.

Do I need a tax ID number to file taxes if I am unemployed?

Yes. Even if you have no income, you use your Social Security number as your tax ID when filing. If you are self-employed or have other business income, you may also need an EIN depending on your business structure.

How long does it take to get an EIN?

If you explore online through the IRS website, you receive your EIN when ready and can use it right away. If you explore by mail or fax, the IRS typically issues the number within two to four weeks. You will receive a confirmation letter by mail.

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.