A Tax Identification Number (TIN) is a unique numeric identifier assigned by a government tax authority to people and entities for tax administration and reporting. In the United States the term “Taxpayer Identification Number” is used by the IRS; a TIN can be a Social Security number (SSN) or one of several IRS-issued numbers used by individuals, businesses, estates, trusts, and other entities.
Key takeaways
– A TIN identifies taxpayers to the tax authority and is used for filing returns, reporting income, and claiming tax benefits.
– In the U.S., common TINs are SSN, Employer Identification Number (EIN), Individual Taxpayer Identification Number (ITIN), Adoption Taxpayer Identification Number (ATIN), and Preparer Tax Identification Number (PTIN).
– TINs are sensitive personal information and are not publicly searchable; use care when sharing.
– Almost every country uses some form of TIN (e.g., Canada’s Social Insurance Number, EU member-state TINs) for taxation and related government services.
Types of U.S. TINs (what they are and who they’re for)
– Social Security Number (SSN): issued by the Social Security Administration (SSA) primarily to U.S. citizens, permanent residents, and certain temporary residents eligible to work. It’s the most common TIN for individuals. (SSA)
– Employer Identification Number (EIN): issued by the IRS to businesses, partnerships, corporations, estates, trusts, and certain nonprofits. Used for employer reporting, business tax filings, and opening business accounts. (IRS)
– Individual Taxpayer Identification Number (ITIN): issued by the IRS to individuals who need a U.S. taxpayer identification number but are not eligible for an SSN (nonresident aliens, certain resident aliens, dependents/spouses of U.S. taxpayers). ITINs do not authorize work. (IRS)
– Adoption Taxpayer Identification Number (ATIN): temporary number for a child in the process of adoption who does not yet have an SSN. (IRS)
– Preparer Tax Identification Number (PTIN): issued to paid tax return preparers who prepare or assist in preparing U.S. federal tax returns. (IRS)
When is a TIN required?
– Filing a federal tax return or claiming tax credits/deductions (e.g., claiming dependents). For example, a parent must have an SSN for a child before claiming that child as a dependent. (IRS)
– Employment and payroll reporting — employers must collect SSNs from employees for wage and tax reporting. (SSA/IRS)
– Business reporting — banks and the IRS require an EIN to open business accounts, file employment taxes, or report certain payments. (IRS)
– Financial institutions often require a TIN to report interest, dividends, and to satisfy U.S. tax identification rules (and for compliance with FATCA/CRS) when dealing with foreign investors. (IRS; international guidance)
– Government benefits and certain licensing or registration processes typically require a TIN.
Who needs a TIN?
– Individuals who file U.S. tax returns, receive income reportable to the IRS, or are claimed as dependents.
– Employers, partnerships, corporations, nonprofits, estates, and trusts for federal tax purposes.
– Non-U.S. persons engaged in U.S. trade or investment or who receive U.S.-sourced income that’s reportable to the IRS often need an ITIN or EIN.
– Paid tax preparers need a PTIN for preparing federal tax returns.
Are TINs available online?
– You cannot look up or retrieve someone else’s TIN online because TINs are sensitive personal information.
– You can apply for certain TINs online: for example, most entities and individuals can apply for an EIN online through the IRS website; some applicants can apply for SSNs in-person at SSA offices or mail the application; the PTIN application is online; ITIN applications generally use mail, in-person IRS Taxpayer Assistance Centers, or Certifying Acceptance Agents (CAAs). (IRS, SSA)
– Authorized payers and some filers can use IRS TIN-matching services (e.g., for 1099 payee name/TIN verification) but this is not a public lookup. (IRS)
Is a Taxpayer Identification Number the same as a Social Security number?
– A Social Security number (SSN) is one type of TIN used by individuals in the U.S. for employment, Social Security benefits, and tax reporting.
– TIN is a broader term that includes SSNs and other identifiers (EIN, ITIN, ATIN, PTIN). SSNs grant work authorization (for those eligible); ITINs do not.
Global TINs
– Most countries issue TINs or equivalent identifiers for taxation and related services: Canada issues Social Insurance Numbers (SINs), EU countries each have TINs for residents and taxpayers, and many other jurisdictions maintain tax ID systems. Rules and formats vary by country. (Government of Canada; European Commission)
Practical steps — how to get the common U.S. TINs
1) Get an SSN (if eligible)
• Who should apply: U.S. citizens, lawful permanent residents, and noncitizens who have authorization to work in the U.S.
• How to apply: Complete Form SS-5 (Application for a Social Security Card) and submit to the SSA with original or certified identity and immigration documents (passport, birth certificate, I-551, work authorization documents). Many applications require an in-person visit to an SSA office or mailing the documents as instructed by SSA. (SSA: Social Security Number & Card)
• Typical use: employment, Social Security benefits, individual tax filing.
2) Get an EIN (for businesses and certain trusts/estates)
• Who should apply: business entities, employers, certain trusts, estates, nonprofits.
• How to apply: Apply online (for entities with a principal business in the U.S.) or by mail/fax using IRS Form SS-4. Online issuance is immediate if eligible. (IRS: Employer Identification Number)
• Tips: Keep the EIN confirmation letter (CP 575) for your records; banks often require it to open business accounts.
3) Get an ITIN (for individuals not eligible for an SSN but who need a U.S. TIN)
• Who should apply: nonresident aliens, resident aliens (based on days of presence) who are not eligible for an SSN but must file a U.S. tax return, or be listed on a return as a spouse or dependent. ITIN does not permit lawful employment. (IRS: Individual Taxpayer Identification Number)
• How to apply: Complete IRS Form W-7 and attach required original or certified documents proving identity and foreign status (passport is preferred). Submit with the federal tax return (unless an exception applies) to the IRS, or use a Certifying Acceptance Agent (CAA) or visit an IRS Taxpayer Assistance Center that accepts ITIN documentation.
• Processing: Allow several weeks; follow current IRS guidance for timelines.
4) Get an ATIN (for adoptions)
• Who should apply: adoptive parents when the child is a U.S. citizen being adopted internationally, or a foreign child being adopted by U.S. citizens, and the child doesn’t yet have an SSN. (IRS: Adoption Taxpayer Identification Number)
• How to apply: File Form W-7A. ATINs are temporary and used until an SSN is issued after final adoption.
5) Get a PTIN (for paid tax preparers)
• Who should apply: any paid federal tax return preparer.
• How to apply: Create an IRS account and register online on the IRS PTIN system. Renew annually. (IRS: PTIN Requirements)
Practical steps — for employers and payers
– Collect the employee’s SSN on Form W-4 and verify it. Employers can use SSA’s Social Security Number Verification Service (SSNVS) or IRS TIN Matching (for certain payee TIN/name matching for information returns) if eligible. These are secure, authorized services — not public searches. (SSA; IRS)
Practical steps — what to do if you lose or need to replace a TIN document
– Lost SSN card: Replace via SSA using Form SS-5 with required documents proving identity and citizenship/immigration status. Limit on number of replacement cards may apply. (SSA)
– Lost EIN: The EIN itself doesn’t change; contact the IRS Business & Specialty Tax Line or retrieve the original EIN assignment letter from your records. (IRS)
– Lost ITIN assignment letter: Contact the IRS ITIN unit for help; do not create a new application unless instructed.
Practical security tips
– Do not share your TIN/SSN unless absolutely necessary (employers, banks for tax reporting, authorized government agencies).
– Store official letters/cards in a secure place.
– Monitor credit reports and consider a credit freeze if identity theft is suspected.
– Use secure methods (encrypted email, secure portals) when sharing TINs with tax preparers or financial institutions.
Common FAQs
– Can a nonresident work with an ITIN? No. An ITIN does not authorize employment. Noncitizens who will work in the U.S. should obtain an SSN (if eligible) and appropriate immigration work authorization. (IRS; SSA)
– Can someone get a TIN instantly? Some numbers (EINs) can be issued immediately online if criteria are met. SSNs and ITINs typically require document verification and processing time.
– Can you look up someone else’s TIN online? No — TINs are confidential; the IRS provides specific, secure services for authorized users (e.g., TIN Matching).
When to contact the IRS or SSA
– IRS: questions about EINs, ITINs, ATINs, PTINs, or tax-facing TIN requirements (irs.gov).
– SSA: questions about SSN issuance, replacement, or card policies (ssa.gov).
The bottom line
A TIN is a critical identifier for tax administration. In the U.S., an SSN is the most common TIN for individuals who are authorized to work; other TINs (EIN, ITIN, ATIN, PTIN) serve businesses, non-worker individuals, adoptive situations, and tax preparers. Apply through the appropriate agency (SSA or IRS), protect your TIN carefully, and use authorized IRS/SSA services for verification and replacement.
References and resources
– Investopedia — “Tax Identification Number (TIN)” (background summary)
– Social Security Administration — Social Security Number & Card: /
– Internal Revenue Service — Individual Taxpayer Identification Number (ITIN):
– Internal Revenue Service — Employer Identification Number (EIN):
– Internal Revenue Service — Adoption Taxpayer Identification Number (ATIN):
– Internal Revenue Service — PTIN Requirements for Tax Return Preparers:
– Internal Revenue Service — Qualifying Child Rules / TIN Requirement guidance: /
– Government of Canada — Social Insurance Number Overview:
– European Commission — Taxpayer Identification Number (TIN) information
Editor’s note: The following topics are reserved for upcoming updates and will be expanded with detailed examples and datasets.