Where to find your existing tax ID number

Your tax ID number is already on file with the IRS if you have ever filed a tax return, opened a bank account, or worked for an employer. The fastest way to find it is to look at documents you already have at home. Check your most recent tax return (Form 1040), your W-2 from your employer, your 1099 form from a client or bank, or any letter the IRS sent you. Your tax ID appears on all of these.

If you cannot locate a document, call the IRS directly at 1-800-829-1040. Have your name, date of birth, and current address ready. The IRS can confirm your number over the phone, though wait times are often long. You can also create an account on IRS.gov and log in to view your tax transcript, which displays your tax ID number.

If you are self-employed or own a business, your tax ID may be different from your Social Security number. Sole proprietors often use their Social Security number as their tax ID, but businesses registered as LLCs, S-corps, or C-corps have an Employer Identification Number (EIN) instead. Check any business licenses, bank statements for your business account, or correspondence from the IRS about your business.

Key Takeaways

  • Your tax ID number appears on your most recent tax return, W-2, 1099, or any IRS letter you have received.
  • If you cannot find a document, call the IRS at 1-800-829-1040 with your name, date of birth, and address ready.
  • Self-employed people and business owners may have an Employer Identification Number (EIN) instead of using their Social Security number.
  • You can also log into your IRS account at IRS.gov to view your tax transcript, which shows your tax ID.

Getting a new tax ID if you do not have one

If you have never filed a tax return and do not have a tax ID, you need to determine which type you need. Most individuals use their Social Security number as their tax ID. If you do not have a Social Security number, you can explore for an Individual Taxpayer Identification Number (ITIN) through the IRS using Form W-7. This is a nine-digit number that works like a Social Security number for tax purposes.

To explore for an ITIN, fill out Form W-7 and mail it to the IRS along with a copy of your passport, national ID, or other government-issued identification. The IRS will mail your ITIN to you within two to four weeks. You do not need to be a U.S. citizen to get an ITIN, but you must have a valid reason — usually that you have U.S. income to report or a spouse who is filing a joint return.

If you own a business and need an EIN, you can explore online at IRS.gov for free. The process takes about 15 minutes, and you receive your EIN when ready. You can also explore by phone, fax, or mail, though those routes take longer. You need your Social Security number, business name, business address, and the type of business structure (sole proprietorship, LLC, S-corp, etc.) to explore.

Understanding the difference between Social Security numbers and EINs

A Social Security number is a nine-digit identifier issued by the Social Security Administration. For tax purposes, most individuals use their Social Security number as their tax ID. If you are self-employed as a sole proprietor with no employees, you can file taxes using your Social Security number.

An Employer Identification Number (EIN) is a nine-digit number issued by the IRS specifically for businesses. You need an EIN if you operate as an LLC, partnership, S-corp, or C-corp, or if you are self-employed with employees. Even if you are the only owner, the IRS treats these business structures as separate entities, so they need their own tax ID. Banks also often require an EIN before they will open a business account.

Some self-employed people choose to get an EIN even if they do not legally need one. This keeps your personal Social Security number separate from your business finances, which can be useful for privacy and record-keeping. However, there is no requirement to do so if you are a sole proprietor with no employees.

What to do if your tax ID was lost or compromised

If you believe your Social Security number or EIN has been stolen or misused, contact the IRS when ready. Call 1-800-829-1040 and explain the situation. The IRS can flag your account and monitor it for fraudulent activity. You should also file a report with the Federal Trade Commission at IdentityTheft.gov, which creates an official record of the theft.

If someone has filed a tax return using your number, the IRS will contact you. You will receive a letter explaining the situation and instructions for resolving it. Do not ignore IRS mail about this — respond promptly with the documents they request. You may need to file Form 14039, Identity Theft Affidavit, to prove the return was fraudulent.

For an EIN, the process is similar but simpler because EINs are business numbers, not personal identifiers. Contact the IRS to report the misuse, and they can issue you a new EIN if needed. Keep records of all communication with the IRS about the issue.

Tax ID numbers for different filing situations

Your filing situation determines which tax ID you use. If you are an employee, your employer has your Social Security number on file, and you use it on your W-2 and tax return. If you are a freelancer or contractor, clients will ask for your tax ID on Form 1099-NEC or 1099-MISC. You can provide your Social Security number or an EIN, depending on your business structure.

If you are married and filing jointly, both spouses need their own tax IDs. Each person uses their own Social Security number or ITIN on the return. If one spouse does not have a Social Security number, they can explore for an ITIN using Form W-7.

If you are a business owner with employees, you must have an EIN. Your employees will use their Social Security numbers on their W-2 forms, but your business uses the EIN. If you hire an independent contractor, you will ask them for their tax ID (Social Security number or EIN) to report their payment on a 1099 form.

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 do not have a Social Security number, you can get an ITIN instead. If you own a business structured as an LLC, partnership, or corporation, your business has a separate tax ID called an EIN, even though you personally still have a Social Security number.

How long does it take to get a new tax ID number?

If you are explore for an ITIN by mail, expect two to four weeks. If you explore for an EIN online, you receive it when ready. By phone or fax, EIN applications take about four weeks. If you already have a Social Security number, you do not need to explore for anything — you already have your tax ID.

Can I use my tax ID number before I file my first return?

Yes. Your tax ID is active as soon as it is issued, whether that is when you receive your Social Security number at birth, when you get an ITIN, or when you receive an EIN. You do not have to file a tax return to use your tax ID — employers and banks can use it before you ever file.

What if I lost my Social Security card but know my number?

You do not need the physical card to file taxes or use your tax ID. If you know your nine-digit Social Security number, that is all you need. To replace the card itself, contact the Social Security Administration at 1-800-772-1213 or visit your local Social Security office. The card is just proof of the number; the number itself is what matters for taxes.

Do I need a different tax ID if I move to a different state?

No. Your tax ID does not change when you move. Your Social Security number, ITIN, or EIN stays the same regardless of where you live. You will file your federal return using the same tax ID, though you may need to file a state return in your new state if it has an income tax.