A tax identification number (TIN) is a unique nine-digit number issued by the Social Security Administration or the Internal Revenue Service to anyone who pays taxes (personal or business).

A Tax Identification Number (TIN) is a unique number assigned to taxpayers and used by the Internal Revenue Service (IRS) in its administration of the nation's tax system. What Is a Tax ...

The REAL ID Act, passed in 2005, sets security standards for issuing sources of identification, such as driver's licenses.

If you expect to have to file a U.S. tax return in 2021, and your identification number is expiring, submit a renewal application by completing the Form W-7 and including all required documents.