Where to find your federal tax ID number

Your federal tax ID number appears on documents the IRS has already sent you. If you are a sole proprietor or individual, look for your Social Security number on your tax returns, W-2 forms, or 1099 forms. If you operate as a business entity — a corporation, partnership, LLC, or nonprofit — your Employer Identification Number (EIN) is on your most recent Form 1120, Form 1065, Form 1120-S, or Form 990.

The IRS does not maintain a public lookup tool where you enter a name and retrieve a number. Instead, you reconstruct the number from paperwork you already have. If you cannot locate the original document, the IRS can confirm the number matches your identity through a phone call or mail request, but they will not tell you a number you have forgotten.

If you have never received a federal tax ID — for example, you just started a business and have not yet filed — you will need to request one rather than look one up. The process differs depending on whether you need an EIN or are using your Social Security number.

Key Takeaways

  • Your Social Security number is your federal tax ID if you are self-employed or file as an individual; your EIN is your federal tax ID if you operate a business entity.
  • Check your most recent tax return, W-2, 1099, or business tax form — your federal tax ID will be printed on one of these documents.
  • The IRS does not have a public search tool; you must locate the number yourself or request the IRS confirm it by phone or mail.
  • If you have never received an EIN, you can request one online through the IRS website, by phone, by fax, or by mail using Form SS-4.

Checking your tax documents for your number

Start with any tax return you filed in the past three years. Open your Form 1040 (individual return), Form 1120 (corporate return), Form 1065 (partnership return), or Form 1120-S (S corporation return). Your federal tax ID will be printed in the top-right corner of the first page, usually labeled "EIN" or shown as a nine-digit number with a hyphen in the middle (for example, 12-3456789).

If you do not have a copy of your return, check any W-2 form your employer sent you, or any 1099 form you received from a client or financial institution. Your federal tax ID appears on these forms as well. You can also request a copy of your tax return from the IRS using Form 4506-C, though the IRS charges a fee and processing takes two to four weeks.

If you are looking up an EIN for a business you own but do not have the return handy, check any business bank statements, business loan documents, or correspondence from the IRS. The EIN is often printed on invoices or business licenses as well.

Confirming your number with the IRS directly

If you believe you have the correct number but want to verify it, you can call the IRS Business and Specialty Tax Line at 800-829-4933. Have your Social Security number or business name and address ready. The IRS representative will confirm whether the number you provide matches their records.

This verification is not the same as a lookup. The IRS will not tell you a number you do not already have; they will only confirm that a number you provide is correct. If you are calling about an EIN for a business you own, be prepared to answer questions about the business structure and when it was formed.

You can also request written confirmation by mail. Send a letter to the IRS with your name, address, and the number you want verified. Mail it to the IRS address for your state, which you can find on the IRS website. Response time is typically four to six weeks.

Requesting an EIN if you do not have one

If you have never received an EIN and need one now, the fastest route is the IRS online process at irs.gov/ein. You will need your Social Security number, business name, business address, and the date you started or plan to start the business. The system generates your EIN when ready and displays it on screen; you can print it or save it as a PDF.

Online registration is available Monday through Friday, 7 a.m. to 10 p.m. Eastern time. You do not need to create an IRS account or log in. The process takes about 10 minutes.

If you cannot use the online tool, you can request an EIN by phone at 800-829-4933, by fax using Form SS-4, or by mail. Phone requests are processed when ready during business hours. Fax requests typically receive a response within four business days. Mail requests take two to four weeks.

What to do if you cannot locate your number

If you have filed taxes before but cannot find your federal tax ID anywhere, contact the IRS directly. Call 800-829-4933 with your name, address, and date of birth. The IRS can search their records and confirm your number. This is different from a public lookup — you must be the person or authorized representative of the business to receive the information.

If you are looking up someone else's federal tax ID — for example, a vendor's EIN for a 1099 form — you cannot get it from the IRS. Instead, ask the vendor directly. Many businesses print their EIN on invoices or websites. If the vendor will not provide it, you can search the System for Award Management (SAM) at sam.gov, which lists all businesses registered to do work with the federal government and includes their EIN.

For nonprofits, you can search the IRS Tax Exempt Organization Search at irs.gov/charities. Enter the organization name and state; the search will return the EIN if the organization is recognized as tax-exempt.

Using your federal tax ID for different purposes

Once you have located your federal tax ID, use it consistently on all tax documents, business licenses, and financial accounts. If you are self-employed, use your Social Security number on your Schedule C and Form 1040. If you operate a business entity, use your EIN on all business tax returns and when opening a business bank account.

Some situations require you to provide your federal tax ID to third parties. Employers need your Social Security number to issue a W-2. Clients and financial institutions need your EIN or Social Security number to issue a 1099. Banks need your EIN to open a business account. In each case, you provide the number yourself — the IRS does not share it on your behalf.

If you have changed your business structure — for example, converting a sole proprietorship to an LLC — you may need a new EIN. Consult a tax professional or the IRS to determine whether your situation requires a new number.

Frequently Asked Questions

Can I look up someone else's federal tax ID number?

Not through the IRS. You can ask the person or business directly. For nonprofits, search the IRS Tax Exempt Organization Search. For federal contractors, search the System for Award Management (SAM). For other businesses, you may find the EIN on invoices, websites, or business licenses.

What if I have multiple federal tax IDs?

If you are self-employed, your Social Security number is your only federal tax ID. If you operate multiple business entities, each one has its own EIN. Use the correct number for each entity on its own tax return. Do not mix them.

Do I need to memorize my federal tax ID?

No. Write it down and store it somewhere safe, or keep a copy of a document that shows it. You will need to reference it when filing taxes, opening business accounts, and responding to IRS correspondence, but you do not need to memorize it.

How long does it take to get an EIN if I request one now?

Online requests are processed when ready. Phone requests are processed the same day during business hours. Fax requests take about four business days. Mail requests take two to four weeks. If you need the number urgently, use the online tool or call.

What if the IRS says my number does not match their records?

Double-check that you have the correct number and that you provided your name and address exactly as they appear in IRS records. If the number still does not match, you may have a filing error or identity issue. Contact the IRS by phone to discuss next steps, or consult a tax professional.