What is an SSN?
A Social Security Number (SSN) is a nine-digit identifier issued by the U.S. Social Security Administration (SSA) to U.S. citizens, permanent residents and certain authorized non-immigrants. Originally created in 1936 for tracking Social Security benefits, the SSN has become the de-facto national identifier used for tax filings, employment verification, credit reporting, banking and government services.
Who is eligible?
SSNs are issued to U.S. citizens at birth (or by application), to lawful permanent residents (green card holders), and to non-immigrants with work authorisation (H-1B, L-1, F-1 with OPT/CPT, etc.). Tourists, B-1/B-2 visitors and non-resident investors without work authorisation generally cannot obtain an SSN — they may apply for an ITIN instead.
What is the SSN used for?
Common uses include filing U.S. federal and state income tax returns (Form 1040), Form W-2 wage reporting, Form 1099 contractor reporting, opening U.S. bank and brokerage accounts, applying for U.S. credit and mortgages, and Form I-9 employment eligibility verification. Many of these functions can also be performed with an ITIN or EIN where the SSN is unavailable.
Privacy and identity-theft risk
Because the SSN is widely used and rarely changed, identity theft risk is high. U.S. data-breach disclosure laws — including California’s CCPA/CPRA, the New York SHIELD Act and most U.S. state breach-notification statutes — apply heightened protections to SSNs. The IRS issues Identity Protection PINs (IP PINs) to help victims of tax-related identity theft.
SSN vs. ITIN vs. EIN
SSNs identify individuals; ITINs identify individuals not eligible for an SSN; EINs identify entities. All three are nine-digit numbers, but each has a distinct issuing process, format convention and authorised use.