Where to find your tax ID number

Your tax ID number is printed on documents you already have. If you are an individual, your tax ID is your Social Security number, which appears on your Social Security card, tax returns, and W-2 forms from employers. If you run a business, your tax ID is your Employer Identification Number (EIN), issued by the IRS — you will find it on your EIN assignment letter, business tax returns, and bank account paperwork.

The fastest way to locate your number is to check the documents you received when you first got the ID. For a Social Security number, pull your most recent tax return or W-2. For an EIN, look for the IRS letter that arrived when you registered the business, usually titled "Notice of Approval" or "EIN Assignment Notice." If you cannot find the original paperwork, the IRS website and the Social Security Administration both allow you to search for your number using other identifying information.

Key Takeaways

  • Your Social Security number is your tax ID if you file taxes as an individual; your EIN is your tax ID if you own a business.
  • Social Security numbers appear on your Social Security card, tax returns, and W-2 forms; EINs appear on the IRS assignment letter and business tax returns.
  • The IRS website lets you look up an EIN using your business name and address without logging in.
  • If you lost your Social Security card, the Social Security Administration can issue a replacement, and your number stays the same.

Looking up a Social Security number online

You do not need to create an account to confirm your Social Security number. The Social Security Administration does not publish a public lookup tool, but you can call their customer service line at 1-800-772-1213 (TTY 1-800-325-0778) and speak to a representative who can confirm your number using your name, date of birth, and mother's maiden name.

If you need your number for a tax return and cannot reach the Social Security Administration by phone, use the number on your most recent tax return, W-2, or 1099 form. These documents are official records of your number and are accepted by employers, banks, and the IRS. If you believe your number is incorrect on a tax return, contact the IRS directly at 1-800-829-1040.

Looking up an EIN on the IRS website

The IRS provides a free EIN lookup tool at irs.gov that does not require you to log in. Go to the IRS website, search for "EIN lookup," and select the tool labeled "Employer ID Number (EIN) Lookup." Enter your business legal name and the state where the business is registered. The tool will display your EIN if the business is on file with the IRS.

This lookup works only if your business is already registered with the IRS. If you recently started a business and have not yet received your EIN assignment letter, you may not see results. In that case, check your email for the assignment letter — the IRS typically sends it within two weeks of approval. If you still cannot find it, call the IRS at 1-800-829-4933 and have your business name, address, and date of formation ready.

What to do if you cannot find your number

If you have lost your Social Security card and cannot locate your number anywhere, request a replacement card from the Social Security Administration. You can explore in person at your local Social Security office, by mail, or online at ssa.gov if you have a state-issued ID. The replacement card is free, and your number does not change — the new card straightforward replaces the old one. Processing takes about two weeks.

For an EIN, if you cannot find your assignment letter and the IRS lookup tool does not show results, contact the IRS directly. Have your business legal name, address, and the date you registered the business. The IRS can confirm whether an EIN was issued and provide the number over the phone. If no EIN exists on file, you may need to register the business first.

Using your tax ID number safely

Your tax ID number is sensitive information. Share it only with employers, banks, the IRS, and other organizations that have a legitimate business reason to request it. Do not post it on social media, include it in unencrypted emails, or give it to someone who calls you unsolicited.

If you suspect your Social Security number or EIN has been stolen or misused, contact the IRS when ready. For Social Security number fraud, call 1-800-269-0271 or visit the Social Security Administration's fraud reporting page. For EIN fraud, call the IRS at 1-800-829-1040. The sooner you report the issue, the faster the IRS can investigate and protect your account.

Tax ID numbers for different business structures

Most businesses need an EIN, but the rules depend on how the business is structured. Sole proprietors without employees can use their Social Security number instead of an EIN, though many choose to get an EIN for privacy and banking reasons. Partnerships, corporations, LLCs, and nonprofits must have an EIN.

If you are unsure whether your business needs an EIN, the IRS website has a tool that walks you through the decision. You can also call the IRS at 1-800-829-4933 and ask. Getting an EIN is free and takes about 15 minutes online through the IRS website, or you can explore by mail or fax.

Frequently Asked Questions

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

No. Tax ID numbers are private information. The IRS and Social Security Administration do not release them to the public. If you need someone's EIN for business purposes, ask them directly — they are required to provide it if you request it for legitimate reasons like payroll or contracting.

What if the IRS lookup tool says my EIN does not exist?

The tool searches only registered businesses. If your business is new, the IRS may not have processed the registration yet. Check your email for the assignment letter, which can take up to two weeks. If you registered more than two weeks ago and still have not received it, call the IRS at 1-800-829-4933 with your business details.

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

Yes, if you are an individual filing taxes. Your Social Security number is your tax ID. If you own a business, your business has a separate tax ID called an EIN, which is different from your personal Social Security number.

Do I need to memorize my tax ID number?

No. Keep it written down in a safe place, like a locked drawer or password manager. You will need it when filing taxes, opening a business bank account, or hiring employees, but you do not need to memorize it. Always verify the number on official documents before submitting it.