Taxpayer Identification Number (TIN)
A Taxpayer Identification Number (TIN) is a unique nine-digit identifier used to identify taxpayers for tax administration. The Internal Revenue Service (IRS) uses TINs to process tax returns, report income, and track taxpayer accounts. Social Security numbers (SSNs) are one common type of TIN.
Key points
- TINs are nine-digit numbers used to identify individuals and entities for tax purposes.
- The IRS issues most UINs (Unique Identification Numbers), while the Social Security Administration issues SSNs.
- A TIN must be included on tax returns and many tax-related documents; it is also commonly requested for employment, credit, and government benefits.
Common types of TINs
- Social Security Number (SSN)
- Issued by the Social Security Administration to U.S. citizens, permanent residents, and certain temporary residents.
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Format: XXX-XX-XXXX. Required for legal employment and Social Security benefits.
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Individual Taxpayer Identification Number (ITIN)
- Issued by the IRS to certain nonresident and resident aliens, their spouses, and dependents who are ineligible for an SSN.
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Format: XXX-XX-XXXX and always begins with a 9. Applicants use Form W-7 and supporting documents.
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Employer Identification Number (EIN)
- Issued by the IRS to businesses, trusts, estates, and other entities.
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Format: XX-XXXXXXX. Used to report employer tax obligations, business income, and other entity-level tax filings.
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Adoption Taxpayer Identification Number (ATIN)
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Temporary number for children in domestic adoption proceedings when an SSN is not yet available. The child must be a U.S. citizen or permanent resident and the adoption must be pending.
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Preparer Tax Identification Number (PTIN)
- Required for paid tax return preparers to include on each return they prepare.
Note: A child must generally have an SSN before a parent can claim them as a dependent on a tax return.
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When a TIN is required
- Filing federal tax returns with the IRS (individuals and entities).
- Employment — employers request SSNs to verify work authorization and report wages.
- Credit and financial services — banks and lenders use SSNs on applications and to report to credit bureaus.
- State tax filings — states may issue separate identification numbers for business tax purposes.
Global use
Most countries use some form of taxpayer or national identification number for taxation, employment, benefits, and credit. Examples:
* Canada: Social Insurance Number (SIN), formatted XXX-XXX-XXX.
* European Union: member countries use national TINs to identify taxpayers and facilitate cross-border tax matters.
Practical notes
- TINs are sensitive personal information and are not publicly available online. Agencies issue official documentation when a TIN is assigned.
- An SSN is a type of TIN but not the only one; businesses and other entities use EINs, and certain individuals use ITINs or ATINs depending on eligibility.
Bottom line
TINs are essential identifiers for tax administration, employment, credit, and government benefits. Individuals, businesses, trusts, estates, and other entities must use the appropriate TIN when filing tax returns and conducting tax-related transactions.
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Sources
- Internal Revenue Service (IRS) — Individual Taxpayer Identification Number, Employer Identification Number, Adoption TIN, PTIN guidance
- Social Security Administration — Social Security Number & Card
- Government of Canada — Social Insurance Number overview
- European Commission — Taxpayer Identification Number guidance