A tax identification number, commonly referred to as a TIN, is a unique identifier assigned by a tax authority to individuals or businesses for the purpose of taxation and other related activities.
In the United States, for instance, the Internal Revenue Service (IRS) issues a nine-digit Taxpayer Identification Number (TIN) to individuals and businesses. This number is used to identify taxpayers in the tax system, track their tax-related activities, and ensure compliance with tax laws.