Your Tax ID is on documents you already have

Your tax identification number is printed on several documents the IRS or your state has already sent you. The fastest way to find it is to look at a past tax return, a W-2 form from an employer, or a 1099 form from a client or bank. If you filed taxes last year, that return shows your number at the top.

If you do not have those documents, the IRS can tell you your number by phone or mail. You will need to prove who you are — usually with a Social Security number and date of birth. The process takes longer than checking old paperwork, but it is free and does not require you to visit an office.

Key Takeaways

  • Your tax ID appears on any tax return you filed, any W-2 from an employer, and any 1099 form from income sources like freelance work or bank interest.
  • If you are a sole proprietor or self-employed, your tax ID is your Social Security number unless you obtained an Employer Identification Number (EIN) from the IRS.
  • The IRS can mail you a transcript of your account that shows your tax ID, or you can call their automated line at 1-800-829-1040 with your Social Security number and date of birth ready.
  • State tax agencies also have records of your tax ID and can provide it by phone or through their online portals if you have a login.

Check your own documents first

Start with any tax paperwork you have kept. A federal tax return (Form 1040, 1040-SR, or 1040-NR) shows your tax ID in the upper right corner. A W-2 form from an employer lists it in box a. A 1099 form — whether 1099-NEC, 1099-MISC, 1099-INT, or another type — shows it in box b. Any of these will give you the number you need.

If you filed taxes through a tax preparation service like H&R Block, TurboTax, or a CPA, you can contact them and ask for a copy of your filed return. Many services keep digital copies in your account for several years. You can also request a transcript directly from the IRS, which is free and includes your tax ID.

Understand the difference between Social Security number and EIN

For most people, the tax ID is simply your Social Security number. The IRS uses it to track your income and tax payments. If you are self-employed as a sole proprietor — meaning you run a business as an individual without forming a corporation or LLC — your Social Security number is your tax ID.

If you formed a business entity (a corporation, partnership, LLC, or nonprofit), you obtained a separate Employer Identification Number (EIN) from the IRS. An EIN is a nine-digit number formatted as XX-XXXXXXX. If you have an EIN, that is your business tax ID, not your Social Security number. You would use the EIN on business tax returns and when hiring employees.

Contact the IRS by phone or mail

The IRS has an automated phone line that can provide your tax ID without speaking to a representative. Call 1-800-829-1040 and follow the prompts. You will need your Social Security number, date of birth, and filing status ready. The system will read your tax ID aloud. This line is available Monday through Friday, 7 a.m. to 7 p.m. your local time.

If you prefer to write, send Form 4506-C (Request for Transcript of Tax Return) to the IRS address for your state. You can find the correct address on the IRS website at irs.gov. Mail requests take 5 to 10 business days. The transcript will show your tax ID and a summary of your filed return. There is no fee for this service.

Use your state tax agency

Your state's tax authority also has a record of your tax ID. Most states maintain online portals where you can log in with your Social Security number and create an account. Once logged in, you can view your tax account and see your ID number. Each state's system works differently, so search for "[your state] tax portal" or "[your state] department of revenue" to find the login page.

You can also call your state's tax agency directly. The phone number is on your state tax return or on the state revenue department website. Have your Social Security number, date of birth, and address ready. State tax staff can confirm your tax ID over the phone, though wait times vary by state and season.

What to do if you have never filed taxes

If you have never filed a federal tax return, you do not have a filed return to look at. In this case, your tax ID is your Social Security number. You do not need to contact the IRS to "activate" or "register" it — the number is valid for tax purposes as soon as you receive it from Social Security.

If you need written confirmation of your Social Security number for a form or application, you can request a Social Security Statement from the Social Security Administration at ssa.gov, or call 1-800-772-1213. You can also use your Social Security card itself as proof of the number.

What if you lost your Social Security card

If your tax ID is your Social Security number and you have lost the card, you can request a replacement from the Social Security Administration. You will need to visit a local Social Security office in person with a photo ID and proof of citizenship or legal residency. Bring documents like a passport, birth certificate, or driver's license. The replacement card is free and usually arrives within two weeks.

While you wait for the card, you already know your Social Security number if you have filed taxes before — it is on any return or W-2 you have kept. If you do not remember the number, use the IRS phone line or state tax portal methods described above to retrieve it.

Frequently Asked Questions

Is my tax ID the same as my Social Security number?

For most people, yes. Your Social Security number is your tax ID unless you formed a business and obtained an EIN. If you are self-employed as a sole proprietor, you still use your Social Security number on your tax return unless you chose to get an EIN.

Can I look up someone else's tax ID?

No. Tax ID numbers are private information. The IRS will only provide a tax ID to the person it belongs to, or to an authorized representative with power of attorney. You cannot retrieve another person's number by calling the IRS or accessing state tax portals.

What if I have multiple tax IDs?

You have one Social Security number for life. If you own multiple businesses, each one may have its own EIN. You would use your Social Security number on your personal tax return and each EIN on the corresponding business return. The IRS can tell you all EINs associated with your Social Security number if you call.

Do I need my tax ID to file taxes this year?

Yes. You need your tax ID before you file. If you are using tax software or working with a tax preparer, they will ask for it early in the process. Gather it from your documents or contact the IRS before you start preparing your return.