A tax identification number (TIN) is a unique number used by tax authorities to identify individuals and businesses for tax-related purposes. It helps track tax payments, process tax returns, and maintain accurate financial records. Depending on the country, a TIN may be issued as a Social Security Number (SSN), Employer Identification Number (EIN), or another government-approved identification number. Individuals and businesses may need a tax identification number when filing taxes, opening financial accounts, or conducting official transactions.