What Your Tax ID Number Is and Where to Find It

Your Tax ID Number Is How the IRS Identifies You for Tax Purposes

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 do not have an SSN or cannot use one, the IRS issues a different nine-digit number called an Individual Taxpayer Identification Number (ITIN).

The number itself looks the same on paper — nine digits in the format XXX-XX-XXXX — but which one you have depends on your immigration status and whether you have a Social Security Number. You need to know which one is yours because tax forms, bank accounts, and government programs ask for it specifically, and giving the wrong number or the wrong type of number can delay processing or cause your documents to be rejected.

Key Takeaways

Your Tax ID Number is either your Social Security Number (if you have one) or an ITIN (if you do not have an SSN but file taxes).
You can find your Tax ID Number on past tax returns, W-2 forms, 1099 forms, Social Security cards, or ITIN letters from the IRS.
If you have lost your number and cannot find it on any document, you can contact the IRS directly by phone or mail to request it.
An ITIN is not the same as an SSN and does not give you work authorization, but it does allow you to file taxes and claim certain credits.

Social Security Number Versus ITIN

A Social Security Number is issued by the Social Security Administration to U.S. citizens, permanent residents, and certain temporary visa holders. It is a nine-digit number that serves as your Tax ID Number automatically. If you have an SSN, you use that number on all tax forms, W-2s, and 1099s.

An Individual Taxpayer Identification Number (ITIN) is issued by the IRS to people who are required to file taxes but do not have an SSN. This includes some non-citizens, undocumented immigrants, and dependents of U.S. citizens who live abroad. An ITIN is also nine digits and looks identical to an SSN on a tax form, but it is not a Social Security Number and does not grant work authorization or any immigration status. It exists only for tax purposes.

The key difference: if you have an SSN, that is your Tax ID Number. If you do not have an SSN but file taxes, your Tax ID Number is your ITIN. You cannot have both — the IRS will assign you one or the other based on your situation.

Where to Find Your Tax ID Number

The fastest way to find your Tax ID Number is to look at a document you already have. Check these in order:

Your Social Security card — your nine-digit number is printed on the front.
A past tax return (Form 1040, 1040-SR, or 1040-NR) — your Tax ID Number appears at the top.
A W-2 form from an employer — your Tax ID Number is in box a (the top left box).
A 1099 form (1099-NEC, 1099-MISC, 1099-INT, or similar) — your Tax ID Number is in box 1 or the top section.
An ITIN assignment letter from the IRS — if you have an ITIN, the IRS sent you a letter with the number when it was issued.
A bank statement or mortgage document — some financial institutions print your Tax ID Number on statements.

If you have an ITIN, the IRS letter that assigned it to you is the official record. Keep that letter in a safe place — you may need to show it to prove your ITIN is valid, especially if you have not filed taxes recently.

How to Request Your Tax ID Number From the IRS

If you cannot find your Tax ID Number on any document, you can contact the IRS directly. The process depends on whether you have an SSN or an ITIN.

If you have a Social Security Number: Call the IRS at 1-800-829-1040 (the main IRS phone line). Have your name, date of birth, and address ready. The IRS can confirm your SSN over the phone. Wait times are often long, especially during tax season (January through April), so call early in the morning or late in the week if possible. You can also visit an IRS office in person — find the nearest one at irs.gov/localoffices.

If you have an ITIN: Call the IRS at 1-800-829-1040 and ask to speak with someone about your ITIN. Have your name, date of birth, and the year you filed your first tax return ready. The IRS can look up your ITIN if you have filed at least one return. If you cannot reach anyone by phone, you can mail Form W-7 (Application for IRS Individual Taxpayer Identification Number) to the IRS address listed in the form instructions, though this takes several weeks.

You can also request a transcript of your tax return from any year you filed — the transcript will show your Tax ID Number. Order a transcript online at irs.gov/transcripts or by calling 1-800-908-9946.

What to Do If Your Tax ID Number Has Been Compromised

If you believe someone has used your Tax ID Number fraudulently — for example, to file a false tax return or open a credit account — contact the IRS immediately. Call 1-800-829-1040 and explain the situation. The IRS has a process for handling identity theft and can flag your account to prevent fraudulent filings.

You should also file a report with the Federal Trade Commission (FTC) at identitytheft.gov. The FTC will create a record of the theft and provide you with a recovery plan. Additionally, contact the three major credit bureaus (Equifax, Experian, and TransUnion) to place a fraud alert on your credit file, which makes it harder for someone to open new accounts in your name.

Keep documentation of all your reports and communications with the IRS and credit bureaus. If you file a tax return and it is rejected because one was already filed using your number, you will need this documentation to prove the fraudulent filing was not yours.

ITIN Renewal and Expiration

ITINs issued before 2013 may have expired or be expiring soon. The IRS implemented a rule that ITINs expire if they have not been used on a tax return for three consecutive years. If your ITIN has expired, you must renew it by filing Form W-7 again.

Check your ITIN assignment letter to see when yours was issued. If it was issued in 2013 or earlier and you have not filed a tax return in the last three years, your ITIN may no longer be valid. You can renew it by mailing Form W-7 to the IRS address in the form instructions. The renewal process takes several weeks, so do this before you need to file your next tax return.

Social Security Numbers do not expire and do not need to be renewed. Once you have an SSN, it remains valid for your entire life.

Frequently Asked Questions

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

If you have a Social Security Number, yes — your SSN is your Tax ID Number. If you do not have an SSN but file taxes, your Tax ID Number is your ITIN instead. You use whichever one you have on all tax forms and documents that ask for a Tax ID Number.

Can I get a Tax ID Number without a Social Security Number?

Yes. You can obtain an ITIN from the IRS by filing Form W-7 (Application for IRS Individual Taxpayer Identification Number). You must include proof of identity and proof of residency with your application. The process takes several weeks by mail. An ITIN allows you to file taxes but does not grant work authorization or change your immigration status.

What if I lost my Social Security card and do not remember my number?

Call the IRS at 1-800-829-1040 with your name, date of birth, and address. They can confirm your SSN over the phone. You can also request a replacement Social Security card from the Social Security Administration at ssa.gov or by visiting a local Social Security office.

Do I need to report my Tax ID Number to my employer?

Yes. When you start a job, your employer will ask for your Tax ID Number on Form W-4 (Employee's Withholding Certificate). Provide your SSN if you have one, or your ITIN if you do not have an SSN. Your employer uses this number to report your wages to the IRS on your W-2 form.

What happens if I give the wrong Tax ID Number on a tax form?

The IRS will likely reject the form or match it to the wrong person's account. If you realize you made an error, contact the IRS or the organization that received the form (your employer, bank, or tax preparer) and provide the correct number. Correcting it quickly prevents delays in processing your taxes or other documents.

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.