Your tax ID number is almost certainly already printed on documents you have at home. For individuals, it’s a nine-digit Social Security Number, or an Individual Taxpayer Identification Number (ITIN) if you aren’t eligible for an SSN. Businesses use a nine-digit Employer Identification Number (EIN). To find your tax ID number, check a past tax return, a W-2 or 1099, your Social Security card, or the IRS notice that originally assigned the number. If none of those turn up, the IRS or Social Security Administration will help you retrieve or replace it for free.
Where Your SSN or ITIN Already Appears
Federal law requires your tax ID on every return or statement you file, so it’s scattered across paperwork you’ve already handled.1Office of the Law Revision Counsel. 26 USC 6109 – Identifying Numbers Check these first:
- Any previous federal tax return. Your SSN or ITIN is printed at the top of every Form 1040.
- Your W-2. Employers report your SSN on the annual wage and tax statement mailed each January.2Internal Revenue Service. General Instructions for Forms W-2 and W-3 (2026)
- 1099 forms. Payers list your tax ID on the 1099-NEC, 1099-MISC, 1099-INT, and similar forms.3Internal Revenue Service. Instructions for Forms 1099-INT and 1099-OID
- Your physical Social Security card, a blue-and-white paper document from the SSA.
- Your ITIN assignment letter, IRS Notice CP 565.4Internal Revenue Service. Understanding Your CP565 Notice
- Bank, mortgage, and lease records. Lenders and landlords collect your SSN for credit checks, so it often appears in account-opening paperwork and loan files.
Once you find your number, store the document somewhere secure. A locked file or safe deposit box works. Loose paperwork with your SSN on it is the easiest route to identity theft.
Where Your EIN Already Appears
An EIN is the federal tax ID assigned to businesses, nonprofits, and other entities.5Internal Revenue Service. Employer Identification Number If you need to locate yours, look at:
- The CP 575 notice. The IRS mails this when it first assigns the EIN, and it’s the most reliable single document for confirming the number.
- Business bank account paperwork. Banks require an EIN to open a business account.
- Payroll tax filings. Your EIN appears on every Form 941 and Form 940.6Internal Revenue Service. Publication 15 (2026), (Circular E), Employer’s Tax Guide
- Business licenses, sales tax permits, and certificates of authority.
- Any business loan application on file with a lender.
Looking Up Your Tax ID Online
If paper records aren’t handy, two free online tools can help you confirm your number.
IRS Online Account
The IRS offers a free individual online account that lets you view W-2s, certain 1099s, and tax return transcripts.7Internal Revenue Service. Online Account for Individuals Because those documents carry your SSN or ITIN, they can confirm your number. One caveat: the IRS partially masks personally identifiable information on transcripts for security, so the full number may not appear on every document.8Internal Revenue Service. Get Your Tax Records and Transcripts
My Social Security Account
The SSA’s online portal lets you manage your account and, depending on your situation, apply for a replacement Social Security card without visiting an office.9Social Security Administration. Replace Social Security Card If you already know the number and just want to verify it, logging in is enough.
Replacing a Lost Social Security Card
You often don’t need a physical card. Most employers and agencies accept the number verbally or through other records. But if you do need a replacement, the SSA issues one at no charge.9Social Security Administration. Replace Social Security Card
Depending on your state and situation, you may be able to apply online. Otherwise, schedule an appointment at your local Social Security office. Either way you’ll need proof of identity, ideally a primary document: a U.S. driver’s license, a state-issued ID card, or a U.S. passport. If you don’t have one of those, the SSA will accept certain secondary documents such as an employee ID, school ID, non-Medicare health insurance card, or U.S. military ID.10Social Security Administration. Learn What Documents You Will Need to Get a Social Security Card Everything must be an original or a copy certified by the issuing agency. Photocopies and notarized copies don’t count.
Once your application is complete, cards typically arrive in 5 to 10 business days. Mail-in applications can take two to four weeks.11Social Security Administration. How Long Will It Take to Get a Social Security Card You’re limited to three replacements per year and ten in your lifetime, though name changes and immigration-status updates don’t count against those limits, and the SSA can grant hardship exceptions.12Social Security Administration. 20 CFR 422.103 – Social Security Number Cards
Retrieving or Renewing an ITIN
If you’ve lost the CP 565 notice that assigned your ITIN, call the IRS at 800-829-1040 (7 a.m. to 7 p.m. local time), or 267-941-1000 from outside the United States.13Internal Revenue Service. Individual Taxpayer Identification Number (ITIN)
Before you use an old ITIN, check whether it’s still active. An ITIN expires automatically if you don’t use it on a federal tax return for three consecutive tax years. Filing with an expired ITIN can delay your return and cost you eligibility for certain tax credits, which may reduce a refund or trigger penalties and interest.14Internal Revenue Service. How to Renew an ITIN
To renew, complete Form W-7 and check the box marked “Renew an existing ITIN.” The steps mirror the original application. One exception: if your ITIN appears only on information returns reporting payments to you, like a 1099, you don’t need to renew it. Expired ITINs still work on those forms.
Retrieving a Lost EIN
If your EIN isn’t in any business record you can find, call the IRS Business and Specialty Tax Line at 800-829-4933. It’s open Monday through Friday, 7 a.m. to 7 p.m. local time, with Alaska and Hawaii on Pacific time.5Internal Revenue Service. Employer Identification Number The representative will verify your identity and confirm you’re authorized to receive the number before releasing it.
If you’re not the business owner, the owner can authorize you as a representative by filing Form 2848 (Power of Attorney and Declaration of Representative). For an EIN request, list “EIN Application” as the matter and “Form SS-4” as the tax form number.15Internal Revenue Service. Instructions for Form 2848 EIN authorizations aren’t kept on the IRS’s centralized file, so you’ll mail or fax the completed form to the office handling the matter.
A Note on Adoption Taxpayer Identification Numbers
If you claimed a child with a pending domestic adoption on your taxes, the IRS may have issued an Adoption Taxpayer Identification Number (ATIN) as a temporary tax ID while the adoption was underway.16Internal Revenue Service. Adoption Taxpayer Identification Number To find a previously assigned ATIN, check your copy of Form W-7A, the application you filed to obtain it. Any IRS correspondence about the adoption tax credit will also list the number. If neither turns up, contact the IRS for assistance.
What Happens If You Can’t Furnish a Tax ID
When a bank, employer, or other payer asks for your tax ID and you don’t provide it, you can be penalized $50 per failure, up to $100,000 per calendar year.17eCFR. 26 CFR 301.6723-1 – Failure to Comply With Other Information Reporting Requirements Payers without a valid TIN on file may also be required to withhold a portion of your payments and remit it to the IRS under backup withholding rules. Businesses that file information returns like 1099s and W-2s with missing or wrong TINs face their own tiered penalties, which grow the longer the error goes uncorrected.18Internal Revenue Service. Information Return Penalties
Protecting the Number Once You Have It
If you’re worried someone else might file a return using your SSN or ITIN, enroll in the IRS Identity Protection PIN program. An IP PIN is a six-digit code that must be included on your federal tax return, which blocks most fraudulent filings in your name.
Anyone with an SSN or ITIN who can verify their identity is eligible, and parents or legal guardians can request an IP PIN for dependents. The easiest route is your IRS online account. If you can’t set one up, you may qualify to apply by mail using Form 15227, provided your adjusted gross income on your most recent return was under $84,000, or $168,000 for married filing jointly.19Internal Revenue Service. Get an Identity Protection PIN