Where to Find Your Federal Tax ID Number

Your federal tax ID number is printed on documents the IRS has already sent you. If you are a sole proprietor or individual, your Social Security number is your federal tax ID. If you operate as a business entity—a corporation, partnership, LLC, or nonprofit—you have a separate Employer Identification Number (EIN), which the IRS issued when you registered that entity.

The fastest way to locate it is to check paperwork you received from the IRS. For an EIN, look for the IRS Form SS-4 confirmation letter, which arrived by mail when you first obtained the number. For a Social Security number, check your Social Security card, tax return, W-2, or 1099 form. If you cannot find the original documents, the IRS website and your own records can help you retrieve it.

Key Takeaways

  • If you are self-employed or a sole proprietor, your federal tax ID is your Social Security number.
  • If you operate a business entity, your federal tax ID is your EIN, which you received from the IRS on Form SS-4.
  • You can look up an EIN you have lost by calling the IRS Business and Specialty Tax Line at 1-800-829-4933 or by checking your past tax returns and business records.
  • The IRS online EIN lookup tool at irs.gov lets you search for an EIN if you registered it within the last 60 days.

Check Your IRS Correspondence and Tax Documents

The IRS mails a confirmation letter when you first obtain an EIN. This letter, Form SS-4 or a similar notice, contains your EIN and the date it was assigned. If you filed a business tax return, your EIN appears on the first page. Check any 1099 forms you issued to contractors, W-2 forms you issued to employees, or quarterly estimated tax payment records—all of these display your EIN.

For a Social Security number, check your original Social Security card, any tax return you filed, a W-2 from an employer, or a 1099 form you received. These documents are usually in a file with other tax or financial records. If you have filed taxes before, your number is on every return you submitted.

Use the IRS Online EIN Lookup Tool

The IRS offers an online search tool at irs.gov that lets you look up an EIN you registered within the last 60 days. Go to the IRS website, navigate to the "explore for an EIN" section, and select the option to check the status of an EIN process or retrieve a recently assigned number. You will need to enter your business name, the state where it is registered, and the date you applied.

This tool works only for EINs issued in the past two months. If your EIN is older than that, or if the online tool does not find it, you will need to contact the IRS directly or review your own business records. Keep in mind that the online tool is available during business hours and may be temporarily unavailable during system maintenance.

Call the IRS Business and Specialty Tax Line

The IRS Business and Specialty Tax Line at 1-800-829-4933 can help you locate a lost EIN. Have your business name, the state where you registered it, and your Social Security number or personal identification number ready when you call. The line is open Monday through Friday, 7 a.m. to 7 p.m. Eastern time. Wait times are often shorter early in the morning or late in the afternoon.

When you reach a representative, explain that you need to retrieve an EIN you have already been assigned. They will ask you to verify your identity and business information, then provide the number over the phone. Ask them to confirm the spelling of your business name and the date the EIN was issued so you have accurate information for your records.

Search Your Business Bank and Accounting Records

Your EIN appears on every piece of correspondence from your bank, accountant, or bookkeeper. Check your business bank account opening documents, loan applications, merchant account paperwork, or any correspondence from your accountant or tax preparer. Banks print the EIN on account statements and checks. If you use accounting software like QuickBooks or FreshBooks, the EIN is stored in your company settings.

If you filed quarterly estimated tax payments, the payment confirmation or receipt will show your EIN. Payroll records, if you have employees, also display the number on every payroll tax form filed with the IRS. Insurance policies and business licenses may include it as well. Gather several of these documents so you have the number confirmed in more than one place.

Request a Transcript from the IRS

If you cannot locate your EIN through any other method, you can request a business tax return transcript from the IRS. This transcript will show your EIN, the tax year, and basic information from your return. You can order a transcript online at irs.gov/transcripts, by phone at 1-800-829-1040, or by mail using Form 4506-C.

Online ordering is the fastest option and usually takes one to two business days. By phone, you can receive the transcript when ready, though you may need to wait on hold. By mail, allow 5 to 10 business days. You will need to verify your identity and provide your business name and the tax year for which you want the transcript. The transcript is free and will clearly display your EIN at the top of the document.

Understand the Difference Between Your Social Security Number and EIN

If you are a sole proprietor—you own a business by yourself and have not formed a separate legal entity—your federal tax ID is your Social Security number. You do not need an EIN unless you have employees or operate as a corporation, partnership, or LLC. Many sole proprietors use their Social Security number on all business documents and tax forms.

If you have formed a business entity, the IRS treats it as a separate taxpayer and assigns it an EIN instead. This number is used for all business tax filings, payroll, and bank accounts in the business name. You keep your Social Security number for personal tax purposes. Some sole proprietors choose to obtain an EIN anyway for privacy or business organization reasons, even though it is not required.

Frequently Asked Questions

What if I cannot remember when I registered my business?

Check your business formation documents—the articles of incorporation, LLC operating agreement, or partnership agreement filed with your state. These documents show the date you officially registered. You can also contact your state's Secretary of State office, which maintains a public record of all registered businesses and the dates they were established.

Can I look up someone else's EIN?

The IRS does not publicly release EIN information for privacy reasons. You cannot search for another person's or business's EIN using the IRS lookup tool. However, if a business has issued you a 1099 form, that form will display the business's EIN. You can also ask the business directly for its EIN if you need it for banking or payment purposes.

What if the IRS says my EIN was never issued?

If the IRS cannot find a record of your EIN, you may need to explore for a new one. This can happen if your original process was lost or never processed. Contact the IRS at 1-800-829-4933 to confirm whether you need to reapply, and they can walk you through the process. Keep records of your new EIN once it is issued.

Do I need my EIN to file taxes as a sole proprietor?

No. As a sole proprietor without employees, you can file taxes using your Social Security number. An EIN is required only if you have employees, operate as a corporation or partnership, or are a nonprofit organization. Some sole proprietors obtain an EIN for business banking or privacy reasons, but it is not legally required for tax purposes.