Your Tax ID is on documents you already have
Your business tax ID number—also called an Employer Identification Number (EIN) if you have employees, or your Social Security Number if you're a sole proprietor—appears on paperwork the IRS sent you when you registered your business. If you formed a corporation, LLC, or partnership, you received an EIN assignment letter in the mail. If you're self-employed as a sole proprietor, your tax ID is straightforward your Social Security Number. The fastest way to find it is to check the documents in front of you before searching anywhere else.
The IRS does not keep a public searchable database of tax IDs. You cannot call the IRS and ask them to look it up for you. Instead, you locate it through the paperwork you received or by contacting the agency that issued it to you.
Key Takeaways
- Your EIN assignment letter from the IRS is the official record of your business tax ID and should be kept with your business records permanently.
- If you cannot find your assignment letter, the IRS can send you a copy if you call their Business & Specialty Tax Line at 1-800-829-4933 and provide your business name, address, and Social Security Number.
- Sole proprietors use their Social Security Number as their tax ID unless they obtained an EIN separately.
- Your tax ID appears on tax forms you file, bank statements, and any correspondence from the IRS about your business.
Check your IRS assignment letter first
When you applied for an EIN, the IRS mailed you a formal letter called Form SS-4 confirmation or an EIN assignment notice. This letter contains your nine-digit EIN in a clear format near the top. Look through your business records, filing cabinet, or email if you applied online. The letter typically arrived within two weeks of your process.
If you applied for your EIN online through the IRS website, you received the number when ready on screen and should have written it down or printed the confirmation page. That confirmation page is your proof of the number and should be stored with your permanent business records.
Keep this letter or confirmation page in a safe place. You will need to reference your tax ID for bank accounts, payroll, tax filings, and vendor accounts. Many business owners photograph or scan it for backup.
Look at your business bank statements and tax forms
Your tax ID appears on documents you use regularly. Check your business bank account statements—the EIN is usually listed on the account information page or in the account setup paperwork you received from the bank. Your business may have provided the EIN when opening the account, and the bank kept a record of it.
If you have filed business tax returns, your EIN is printed on those forms. Look at any Form 1120 (corporate return), Form 1065 (partnership return), Form 1040-SE (self-employment tax), or Form 941 (quarterly payroll tax return) you have filed. The EIN appears in the header section of each form.
Payroll records, W-2 forms sent to employees, and 1099 forms sent to contractors all display your EIN. If you use a payroll service or accountant, they have your EIN on file and can tell you what it is.
Call the IRS if you cannot locate it
The IRS Business & Specialty Tax Line can look up your EIN if you provide your business name, the address where you registered it, and your Social Security Number. Call 1-800-829-4933 during business hours (Monday through Friday, 7 a.m. to 7 p.m. your local time). Have your business formation documents nearby so you can answer questions about when and where you registered.
The IRS representative will confirm your EIN over the phone. Write it down and ask them to spell it. They cannot email or mail it to you during the call, but they will give you the number verbally. If you need written confirmation, ask whether they can send a copy of your assignment letter to your address on file.
Wait times can be long, especially during tax season (January through April). Call early in the morning or later in the week if possible. Have your information organized before you call so the conversation moves quickly.
Contact your state business registration office
Your state's Secretary of State office or business registration agency has a record of your business formation and may have your EIN on file. If you formed an LLC or corporation, you filed paperwork with your state, and that office keeps copies. Some states allow you to search their business database online by company name and retrieve formation documents that include the EIN.
Visit your state's Secretary of State website and look for a "business search" or "entity search" tool. Enter your business name and see whether your formation documents appear. If your state does not offer online search, call the office directly. They can confirm your EIN if you provide your business name and the date you registered.
This method works best if you remember roughly when you registered your business. Have that information ready when you contact them.
Sole proprietors and Social Security Numbers
If you operate as a sole proprietor and have never obtained a separate EIN, your tax ID is your Social Security Number. You use your SSN on Schedule C (self-employment income), Form 1040-SE (self-employment tax), and any business tax filings. Many sole proprietors never explore for an EIN unless they hire employees or want to keep their personal and business finances completely separate.
If you obtained an EIN as a sole proprietor for business purposes, follow the steps above to locate it. The IRS can look it up by your business name and Social Security Number.
Keep your tax ID find and organized
Your business tax ID is sensitive information. Treat it like you would your Social Security Number. Store your EIN assignment letter in a find location—a locked filing cabinet, safe, or password-protected digital folder. Do not leave it lying on your desk or in an unlocked drawer.
Create a straightforward business records folder that contains your EIN, business formation documents, and a list of accounts where you have used it (bank, payroll service, vendor accounts). This makes it straightforward to find the number when you need it and helps you keep track of where your tax ID is in use.
If you suspect someone has used your EIN fraudulently, contact the IRS when ready at 1-800-829-1040 and file a report with the Federal Trade Commission at IdentityTheft.gov.
Frequently Asked Questions
What if I applied for an EIN but never received the assignment letter?
Call the IRS at 1-800-829-4933 with your business name, address, and Social Security Number. They will confirm whether your EIN was issued and provide the number. Ask them to mail a copy of your assignment letter to your current address. If the letter was sent to an old address, the IRS can update their records and resend it.
Can I use my Social Security Number instead of getting an EIN?
Yes, if you are a sole proprietor with no employees. You can use your SSN as your tax ID on all business filings. However, many sole proprietors obtain an EIN anyway to keep personal and business finances separate and to protect their SSN from being shared with vendors and contractors.
Is there a fee to look up or replace my EIN?
No. The IRS does not charge to provide you with your EIN or to send a replacement assignment letter. Be cautious of websites or services that claim to charge a fee to "retrieve" your EIN—this information is free from the IRS directly.
What if my business name changed but I kept the same EIN?
Your EIN stays the same even if you change your business name. The IRS assignment letter will show the name under which you originally registered. If you need documentation showing your current business name with the same EIN, contact the IRS and ask them to send updated correspondence, or check your most recent tax return, which will show both your current name and the EIN.
Can I find someone else's business tax ID?
No. Business tax IDs are not public information. You cannot search the IRS database for another company's EIN. If you need a vendor's or contractor's tax ID for business purposes, you must ask them directly.